ANSYS Maxwell Loss Calculations in a Magnetic Gear

In this video, PADT’s Kang Li shows how to carry out loss calculations from permanent magnets and the core materials.

All Things Ansys 093: Introducing Ansys 2021 R2

 

Published on: July 26th, 2021
With: Eric Miller, Tom Chadwick, Aleksandr Gafarov, Joe Woodward, Ted Harris, Sina Ghods, & Josh Stout
Description:  

In this episode your host and Co-Founder of PADT, Eric Miller is joined by members of the simulation support team to explore Ansys 2021 R2 and discuss their favorite features so far.

Ansys multiphysics software solutions and digital mission engineering help companies innovate and validate like never before. Ansys gives engineers the power to see how their ideas will perform against millions of variables.

Ansys 2021 R2 delivers significant improvements in simulation technology together with nearly unlimited computing power to help engineers across all industries reimagine product design and achieve product development goals that were previously thought impossible.

If you have any questions, comments, or would like to suggest a topic for the next episode, shoot us an email at podcast@padtinc.com we would love to hear from you!

Listen:
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@ANSYS #ANSYS

Friday Flownex Tech Tips #12

Sizing Pumps and Manually Specifying a Pump Curve in Flownex

As a System Engineer you may not always already have equipment decided on for your particular network. Flownex makes it easy to start from scratch and will help determine the equipment necessary to meet the flow or process requirements. In today’s tip we’ll go over how to size a pump using the basic centrifugal pump component and how to manually enter pump curve data. We are using Flownex version 8.12.7.4334

Sizing a Pump

In our example scenario let us pretend we are sizing a pump for a cooling water circuit. We are tasked with finding a pump which will deliver water at a rate of 1 kg/s to the heat exchanger. We know our upstream and downstream boundary conditions as well as the heat added at the exchanger and the speed at which we will be operating the pump.

Choose the appropriate flow component

There are a few different pumps available in Flownex:

Basic Centrifugal Pump: Used when we do not have a pump chart available, particularly useful when sizing a pump.

Fan or Pump: Used when a pump chart is available for modeling either compressible or incompressible flows.

Positive Displacement Pump: Used for modeling rotary and reciprocating pumps where the fluid is incompressible, non-Newtonian, or a slurry.

Variable Speed Pump: Similar to the Fan or Pump but with the ability to interpolate between fan/pump curves for different speeds of rotation.

In this case we’d choose the Basic Centrifugal Pump. This is found in the component pane under Turbos and Pumps. Since we only know the RPM we can enter it in the inputs under Speed at BEP:

Recall we don’t know what the design of the pump will be. Since all we know is that the mass flow rate needs to be 1 kg/s we will check the box for fixed mass flow and then select to change design to target our desired flowrate.

Once we hit solve our pump design inputs will be populated such that our desired mass flow rate is achieved. We can cross-reference these values with available pumps to choose the appropriate component for our network!

Specifying a Pump Curve

If we already know which pump we are using, or perhaps are trying to decide between several available pumps, we may need to add these pump curves to Flownex. To add a pump curve we will navigate to the Charts and Lookup Tables pane > Project Database > Flow Solver > Turbos and Pumps. In this scenario we are looking at a single speed pump so we will right-click on Pump and Fan Charts and Add a Category.

We can name our category whatever is appropriate and then right-click on the newly created category to add our own pump chart.

To edit the newly created pump chart we can either double-click on it or right-click and select edit. Now we simply specify the Reference Density and then fill out the table with the relevant data points. To speed things along we can copy and paste a table of data points from excel or whatever source we get this curve from. Don’t forget to check your units!

Bonus Tip!

Girl Gang Garage: Custom Car Rebuilds + 3D Scanning + 3D Printing

What do you get when you cross a 1961 Volvo PV544 retro-look car with a sleek 2019 Volvo S60 T8 Polestar Engineered sedan – and why would you ever do that?

You get a custom head-turner hybrid vehicle designed to get people talking, especially about women in automotive trades. That’s because this blended vehicle project is being disassembled, redesigned and rebuilt by an all-female team based at Girl Gang Garage in Phoenix Arizona.

Bogi Lateiner and Shawnda Williams, co-owners of Girl Gang Garage, stand next to the stripped-down body of a 1961 Volvo PV544 that will soon be retrofitted on the chassis of a brand-new 2019 Volvo S60 T8 Polestar Engineered sedan. The rebuild project provides a rare hands-on learning opportunity for women of all ages and skill levels, from around the U.S., to come and learn (or improve) skills in welding, cutting, transmission work, body repair/painting, electronics, upholstery and more. (Image courtesy Girl Gang Garage.)

Girl Gang Garage founder and co-owner, Bogi Lateiner, TV host of Motortrend’s All Girls Garage and Garage Squad shows, is well on the way to transforming these vehicles as the third major public project she has undertaken. Along with co-owner Shawnda Williams, Lateiner offers women of all ages, experiences and skill levels the chance to lend a hand, learn a tool, and possibly discover a new career-path in the automotive trades.

The front showroom of Girl Gang Garage (Phoenix AZ). At the left is the group’s second all-female build dubbed High Yellow 56, displayed at the 2019 SEMA Show. Partially hidden in the center is the first (2017) Girl Gang build, the Chevy Montage with its BMW engine, and at the right is the early-stage PV544 rebuild slated for showing at the 2021 SEMA Show. (Image courtesy PADT Inc.)

Lateiner and Williams apply well-honed old-school skills but have been increasingly interested in the possibilities offered by today’s digital workflow. That’s why early in 2021, after conversations with the fellow re-build team at Kindig-It Custom Car Fabrication, Lateiner reached out to Stratasys to see how they might work together to incorporate 3D printing in the PV544 project.

At Stratasys, Pat Carey, Senior Vice President Americas Products & Solutions, and Allen Kreemer, Senior Strategic Applications Engineer, were immediately onboard with the chance to help Girl Gang Garage move into the digital world while widening their circle of women with automotive skills and interests. They loaned the team an F370 FDM 3D printer and accompanying support-removal SCA tank and offered to supply filament material for a two year try-whatever-you-want time period. Moreover, they pulled together a volunteer team of women across the country who could support the effort on multiple fronts.

Every 3D printer looks better with a cool scooter in front: the Stratasys F370 FDM printer, installed at Girl Gang Garage. (Image courtesy PADT Inc.)

A Virtual Team and a Digital Workflow

The team includes engineers whose day-time jobs have them working at Stratasys, Link3D, Autodesk, Xerox, Collins Aerospace and Ford Motor Company or as independent consultants. Printer installation and local support is handled by PADT Inc, a Stratasys reseller and 3D printing/design/simulation company located just 16 miles away from Girl Gang Garage. In addition, members of Women in 3D Printing offered to coordinate many of the publicity efforts and even sponsor a related design competition targeted at young women in high schools and colleges who are learning CAD skills. (More on that to come.)

During the first few Zoom meetings that introduced Lateiner and Williams to the technical capabilities of the different team members and the printer, the basic rebuild plan was presented: strip the PV544 down to bare metal (removing every mechanical and electrical component), disassemble the S60 down to the chassis, engine, drive-train and hybrid motor system, and figure out how to make the two sections fit!

Traditionally, that workflow depended strictly on the classic tools of the trade, from cutting wheels and a Sawzall to hand-grinders and pneumatic drills. Those components are still coming into play on the current project under the skilled eye of the Girl Gang Garage leaders, but now complementary digital processes are being added.

It Starts with Scanning

Using the GOM Tscan Hawk hand-held 3D laser-line scanner to digitally capture reference points, surface curvature and details on the PV544 body. (Image courtesy PADT Inc.)

PADT recently became a reseller of GOM 3D scanning hardware and software tools, and the timing was perfect to bring the new handheld Tscan Hawk system on-site. Operating with both red-line and blue-line (different wavelength) laser scanners plus stereo cameras, the Tscan Hawk captures millions of spatial 3D-point-coordinates (termed clouds of data) which are converted into a standard STL mesh file format for several end-purposes. The red lasers generate measurements across medium to large surfaces while the blue-wavelength sensors capture fine detail, with accuracy down to 20 microns.

GOM Inspect software records reference points, captures the individual coordinate data and allows interrogation of that data to provide dimensions, such as the distance between the engine frame mounts or the diameter of the hole into which the headlamp fits.

 (Images courtesy PADT Inc.)

These three images show a) the reference-point data that appears on the laptop screen as the shape of the PV544 vehicle’s underside is captured, b) the completed scan showing the 3D details of the as-built sheet metal and c) a report page from GOM Inspect software with dozens of dimensions extracted from the scan, such as the length of the trunk opening and the width of the opening available for the engine mount. The scan data, if exported as an STL file, could be sent directly to a 3D printer – though for this project the team is not printing the full body. Instead, subsets of the scan are being used for reverse engineering, where the data works as the basis for creative design elements to be printed and perhaps painted or plated.

To do so, the scanned data is be brought into a surfacing package such as Geomagic Design X or Innovmetric PolyWorks. Those software tools let users convert the STL mesh into an IGES surface, which can then be brought into a CAD package as the basis for a new solid model.

Not for the real build but as a fun example, here is a possible headlight-rim with the letters “Girl Gang Garage” cut out as a circular repeat pattern, that could be backlit with LEDS to customize the build. The design and dimensions are based on the maximum inscribed circle fitted by the GOM Inspect software inside the given opening. (In future blog posts, we’ll show examples of the CAD team’s actual 3D printing results.)

Scanning has many other purposes and capabilities. If CAD data were available for the actual vehicle, those files could be imported, overlaid on the captured data, and compared, alerting the user to deviations between intended and actual dimensions – a very common use of GOM Inspect software.

Next Steps

Every Thursday through Sunday, volunteer women come to Girl Gang Garage and learn to use cutting tools, welders, sanders and more, making daily progress toward the completed hybrid PV544. (All women are invited to come help and learn, at no cost – just sign up to get involved and get yourself to Phoenix.) Here are a few glimpses into the work as of early April – much more has been done but stay tuned for the next blog post as we show off elements of the S60 sedan, scan data being used for reference, and details of the design contest.

Views of the PV544 Volvo with work underway on a rear fender (also shown as scan data from the Tscan Hawk, with Bogi Lateiner in her Girl Gang Garage location). (Images courtesy PADT Inc.)

PADT Inc. is a globally recognized provider of Numerical Simulation, Product Development and 3D Printing products and services. For more information on Stratasys printers and materials, contact us at info@padtinc.com.

ANSYS Maxwell: Building a Magnetic Gear Model

In this video, PADT’s Kang Li steps users through the process of building and running a magnetic gear from scratch in Ansys Maxwell. The model shows both standard magnets and a Halbach array.

Friday Flownex Tech Tips #11

How to use Flow Path Graphs and Increment Plots in Flownex

Flow Path Graphs and Increment Plots can be incredibly useful visualization tools to see how a simulation result varies as a function of length along the axial flow path and to see a higher fidelity result for a single flow component. Use these in Flownex to up your reporting game! In this demo we are using Flownex version 8.12.7.4334

Creating a Flow Path

A flow path is any continuous series of flow elements and can be created by clicking “Flow Paths” in the results ribbon. Once we’ve created our new flow path we define it by choosing our start and end nodes.

Another, simpler, method is to simply drag and drop the nodes onto the flow path start and end point:

If we have a branched network we can add an intermediate node or flow component to our flow path to ensure the correct path is captured in the graph:

Insert a Flow Path Graph

The Flow Path Graph is in the component pane under visualization > graphs. Once the graph is added to the canvas we simply need to drag and drop our newly created flow path onto the graph and choose the characteristic we are interested in plotting. We will need to drag and drop the flow path for each characteristic we would like plotted.

How to create Increment Plots

You may have noticed in the previous images that there were many data points on the graphs for each of our flow components. This is because we had each pipe modeled as 25 increments. When we add increments to our flow components Flownex will treat each component as if it were split up that number of increments – solving the conservation equations for each increment rather than once over the entire component. This is helpful when modeling long pipes, capturing pressure waves, or determining exactly where a phase change may happen. A good way to think about this is that it is essentially the same as refining a mesh in a typical finite element analysis.

There is another plot in Flownex we can use for a single flow component that has been incremented. The increment plot is located in the components pane under Visualization > Graphs > Increment Plots. If we were, for example, trying to plot the inside surface temperature of our first pipe in this example network we could use an increment plot to see what is going on.

To create an increment plot we simply drag and drop the plot onto the canvas. We can either selectively drag results from individual increments or multi-select many increments and drag the desired variable onto the graph. Note that since there is a tie of each increment parameter separately there may be some delay if we are multiselecting a very large number of increments.

Bonus Tips!

  • We can use a Flow Path graph for a single component to avoid having to multi-select increments.
  • To create a graph on its own page instead of floating on the canvas go to the Project Explorer pane on the left side of the GUI, select Graphs, then right-click on the Graphs Folder and select Add Graph Page and choose your desired type of plot.

Mini Mechanica clock section of 3D printed Tourbillon Clock at PADT

Three Dimensions of Time: A new, 3D Printed Clock Highlighting PADT’s Additive Capabilities

Tracking time has challenged the human race for centuries, resulting in some of the finest mechanisms ever crafted. From sundials and hourglasses to pocket watches and atomic clocks, we have marked the passage of time with ever-increasing precision. Along the way, we became supremely skilled at creating the requisite gears and springs, as well as the machines to produce them. (If you have a deeper interest in measuring time, one must-read book is Longitude by Dava Sobel.)

This post, however, is about taking clock-making to a new dimension – three dimensions, in fact, using multiple 3D printers to generate not only the gears and structural components but even the watch-spring and winding-key, based on a mechanism called a Tourbillon. Invented around 1800 by Abraham-Louis Breguet, the Tourbillon concept compensates for the effects of gravity on delicate watch-springs when the watch is carried or laid down (varying its orientations), by employing multiple axes.

A traditionally made Tourbillon watch mechanism (watchgecko.com)

An excellent write-up on this concept is on MyMiniFactory, which is also where you’ll find the fascinating design of a 3D-printable Tourbillon clock from a designer called Mechanistic. Check out this mesmerizing video of the clock in action. Mechanistic has previously done other awesome designs and this past Spring did a crowd-funding effort to support printing all the components on a hobby-type 3D printer.

Depending on one’s donation amount, some or all of the intricate clock’s CAD files are downloadable. Recently Justin Baxter, PADT’s senior 3D Printing Service Engineer (with years of hobbyist clock-making under his belt), set out to reproduce the device with a twist. Why not take advantage of all the additive manufacturing systems in use by PADT’s Manufacturing Division, and print at least one component on each?

This approach spans the AM technologies of Fused Deposition Modeling (Stratasys FDM material extrusion), PolyJet (Stratasys material deposition), selective laser sintering (3D Systems SLS polymer powder bed fusion), direct metal laser sintering (EOS DMLS metal powder bed fusion), stereolithography (3D Systems and UnionTech vat SLA photopolymerization) and digital light processing (Stratasys Origin One DLP vat photopolymerization).

The Triple-Axis Tourbillon Mechanical Clock Design

Not all of the clock’s 230 components are 3D printed – metal screws, pins and ball bearings round out the assembly – but Justin is slowly printing all other parts spread across colors, materials and AM technologies. For starters, he has recreated the central first-axis mechanism called the Mini Mechanica; this subset serves well for new users to test out their own systems and parameters ensuring effective dimensional tolerances. The Mini Mechanica part files are also available as a separate free download.

First section of the Mechanist design of a 3D printed, three-axis Tourbillon mechanical clock, printed at PADT based on the downloaded files from MyMiniFactory. (Image courtesy PADT)

Justin’s Mini Mechanica includes the following parts made of ABS (acrylonitrile-butadiene-styrene), each 3D printed on one of our two Stratasys F370 FDM systems:

Part Name
01_Bottom Base
02_Upper_Base
03_Tourbillon_Lower_Cage
04_Tourbillon_Upper_Cage
05_Cage_Bridge
06_Cage_Spacer
07_Ratchet_Post
08_Winder
09_Mainspring
10_Core_Post
11_Impulse_Pin
12_Tourbillon_Ring_Gear
13_Hairspring
14_Balance_Wheel
15_Escape_Fork
16_Escape_Wheel
17_Washer
18_Display_Stand

When finished, here is how that subset will fit into the completed three-axis clock:

Three-axis Tourbillon clock designed for 3D printing by Mechanistic, with part files available by donation on MyMiniFactory (www.myminifactory.com) (MyMiniFactory)

Note: the fully printed clock operates on a 90 minute run-time if a steel spring is employed, and 20 minute run time with a 3D printed (FDM) version. (We’ve seen suggestions for adding a battery.)

For more details on the Triple Axis clock, see the conveniently provided assembly guide: (2) How to build a 3D Printed Triple Axis Tourbillon | Assembly Guide – YouTube.

As the part-builds progress across our other printers and materials, we’ll post an update. Here are a few more components in progress, including the decorative base on the left, which was printed in Nylon 12GS on our SLS powder-bed printer.

In-progress parts 3D printed for the Mechanica Tri-Axis Tourbillon Clock currently being reproduced at PADT. The decorative base at the left was printed in Nylon 12GS on our SLS system; the parts for the MiniMechanica (assembled at the top) and the remaining black and grey parts were printed in ABS and ASA on our Stratasys F370 FDM systems. (Image courtesy PADT Inc.)

PADT Inc. is a globally recognized provider of Numerical Simulation, Product Development and 3D Printing products and services. For more information on Stratasys polymer printers and materials and EOS metal printers, contact us at info@padtinc.com.

An Ansys Licensing Tip – ANSYSLMD_LICENSE_FILE

Most Ansys users make use of floating licensing setups, and I would say the majority of those actually make use of licenses that are hosted nonlocally but on their network. Within this licensing scheme, there are quite a few different tools and utilities that we can use to specify where we pull our licenses, too. One of the methods that is making a comeback (in my recent experience) as far as success in troubleshooting and overall reliability is specifying the environment variable ANSYSLMD_LICENSE_FILE.

This variable allows you to point directly towards one or more license servers using a port@address definition for the FlexNet port. With just this defined, the interconnect port will default to 2325, but if your server setup requires another interconnect port then you can also specify this using the ANSYSLI_SERVERS environment variable with the same format.

The downside is that this is a completely separate license server specification from the typical ansyslmd.ini approach, so any values specified this way will not be visible in the “Ansys Client License Settings” utility. On the upside, this is a completely separate license server specification! Meaning, if there are permission issues associated with ansyslmd.ini, or the other license utilities experienced some unknown errors on installation, this may be able to circumvent those issues entirely.

Also, for more advanced setups this can be used to assign specific license servers to individual users on a machine or to potentially help with controlling the priority of license access if multiple license servers are present. Anyway, this may be worth looking into if you encounter issues with client-side licensing!

Mechanical Updates in Ansys 2021 R2: External Models, Composites & Meshing – Webinar

Ansys Mechanical delivers features to enable faster simulations, easier workflows, journaling, scripting and product integrations that offer more solver capabilities. 

With the Ansys suite of tools, engineers can perform finite element analyses (FEA), customize and automate solutions for structural mechanics challenges and analyze multiple design scenarios. By using this software early in the design cycle, businesses can save costs, reduce the number of design cycles and bring products to market faster.

Join PADT’s Lead mechanical engineer Doug Oatis to discover the new features that have been added to Ansys Mechanical in the first webinar covering the 2021 R2 release.

Highlights include unlimited modeling possibilities with journaling and scripting in the Mechanical interface and increased meshing efficiency and quality for shell meshing, among many others.

Register Here

If this is your first time registering for one of our Bright Talk webinars, simply click the link and fill out the attached form. We promise that the information you provide will only be shared with those promoting the event (PADT).

You will only have to do this once! For all future webinars, you can simply click the link, add the reminder to your calendar and you’re good to go!

All Things Ansys 092: Recap of Ansys 2021 R1 & Beyond

 

Published on: July 12th, 2021
With: Eric Miller, Tom Chadwick, Aleksandr Gafarov, Joe Woodward, Ted Harris, Doug Oatis & Josh Stout
Description:  

In this episode your host and Co-Founder of PADT, Eric Miller is joined by members of the simulation support team to recap Ansys 2021 R1 and discuss expectations and predictions for 2021 R2.

If you have any questions, comments, or would like to suggest a topic for the next episode, shoot us an email at podcast@padtinc.com we would love to hear from you!

Listen:
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@ANSYS #ANSYS

Friday Flownex Tech Tips #10

Rotor-Rotor and Rotor-Stator Cavities

Happy Friday! In today’s tech tip we’ll introduce the rotating components library and demonstrate how to utilize the cavity drawing tool for rotor-stator cavities which can be a huge time-saver when building secondary flow networks. We are working with Flownex version 8.12.7.4334.

Rotating Components

One common implementation of rotating components in Flownex that I see is for modeling secondary flow networks for gas turbines. These flow paths are also sometimes called secondary air systems. What this refers to is the flowpath separate from the primary flowpath (Secondary, get it?). This is flow used to cool equipment, shrouds, discs, vanes, and to provide buffering for the seals to the oil system.

https://flownex.com/industries/gas-turbines/

Flownex has a whole library of rotating components that come in handy when building these secondary flow networks. These are well documented in the Flownex help manuals if you’d like to read up on technical specification, inputs, results, and theory.

  • Custom Vortex
    • A custom vortex is used when velocity profile is between that of a forced vortex and free vortex.
  • Forced Vortex
    • In a forced vortex the fluid moves similar to a solid body with constant angular velocity.
  • Free Vortex
    • Free vortex swirl is calculated using mass flow rate average of the incoming swirl streams, swirl is constant over the radius; usually used for rotating fluid in an open cavity.
  • Labyrinth Seal
    • Used for modeling axial and radial straight and staggered seals.
  • Rotating Annular Gap
    • Used to model flow through an annulus with the inner or outer cylinder rotating.
  • Rotating Channel
    • Used for flow inside channels in rotating discs and blades.
  • Rotating Nozzle
    • Similar to a stationary nozzle where there is a discharge coefficient as a function of the inlet type.
  • Rotor-Rotor Cavity
    • Used when calculating swirl ratio from moment balance on the the rotor surfaces, bolt heads, and flows.
  • Rotor-Stator Cavity
    • Used when calculating swirl ratio from moment balance on the the rotor and stator surfaces, bolt heads, and flows.

Cavity Drawing Tool

Now we get to the nitty gritty of todays tip; how to utilize the cavity drawing tool. When we use either a Rotor-Rotor component or a Rotor-Stator component there are two options for specifying the surface geometry. We can either model as pure radial disks, or as a complex surface specification.

We can use the complex surface specification option to model a rotor-stator cavity like in the cross-section below. When using this option we will need to get a cross-section like this from CAD or from a scaled technical schematic.

To specify this surface geometry we will click the radio button next to surface geometry and add our image to the project. For a refresher on adding an image to your project check out the blog post on adding a background image.

Reference Measurements

We will first need to specify our reference axial and radial coordinates. This is done by dragging the red and blue boxes to known locations on the cross section and entering in the values in our desired units.

Surface Geometry

Now that we have specified the reference measurements we can define our rotor and stator surface geometries. This can be done in the Rotor Surface Geometry ribbon and the Stator Surface Geometry ribbon. The mode in the top right of the GUI lets us know if we are adding points, moving points, or deleting points. To add points we will click and drag from the previous point.

You’ll notice the inner and outer radius fields are automatically updated. This can be a good way to sanity check against known measurements or against CAD. We will need to do the same thing for the stator surface geometry.

Bolts

If there are rotor or stator bolts they may be added in their respective ribbons. The blue lines we see in these images represent the limits of the rotor or stator surface. If bolts are added we will need to click Bolt Details at the bottom of the window and add bolt geometry. The radius fraction is populated automatically and the other inputs will need to be updated as needed by the engineer.

Cavity Shroud

If we need to model the cavity shroud this can be done in the shroud ribbon. In our demonstration today the shroud is included in the rotor and stator surface geometries. For this case we can de-select specify shroud width.

Gap Width

Next we must specify the gap width. To understand what the appropriate width to specify we must dive a little bit into the theory.

Flow regimes for rotor-stator cavity flow can be classified by the following image:

“G” being the gap width ratio (s/a where s is the gap width and a is the outer radius of the cavity) and Re is the Reynolds number for cavity flow. Essentially there are four regimes which are determined by the Reynolds number and gap ratio.

Flownex uses correlations from Haaser et. al (1987) and Daily and Nece (1960) to calculate the required moments produced by the rotor or stator on the fluid within the cavity. Haaser et al. is valid for Regime IV whereas Daily and Nece is valid for 0.0127<=s/a<=0.217 and 1000<=Re<=1e7. It is suggested to use Haaser when the flow is in Regime IV and Daily and Nece when the flow is within the other regions.

I hope I haven’t lost you.

So, for complex geometry (not just two flat surfaces) it is recommended to use the smallest gap width first and calculate the disc Reynolds number. Using the smallest gap width gives you the smallest gap width ratio which will lower the point at which your fluid is in the flow regimes graph above. Now check in what region you are. If your Reynolds number is high enough to be in region IV, and while using the smallest gap width your are still in region IV then it is safe to say that your entire flow will be valid when using Haaser. If this is true, you can then use the smallest gap width because the correlations of Haaser is not dependent on gap width. Using the minimum gap width essentially allows you to make sure that your entire flow is within regime IV. When you have used the smallest gap but see that your gap width ratio and/or Reynolds number leaves you in a different regime (I,II or III), we will then suggest that you calculate the moments using Daily and Nece.

To summarize, start with the smallest gap width and determine the Flow Regime:

If we are in region IV for the smallest gap width then we can leave the gap width as originally specified. If we were in any other region we should change our gap width to be an average:

Don’t forget to specify the correct correlation in the inputs for your rotor stator cavity as well. Big thanks to Leander Kleyn at Flownex for helping me understand the theory behind the gap width!

Discretization of the Cavity

Lastly, we need to assign the discretization of the model. This can be thought of as sort of refining the mesh of the cavity. We can specify more or less increments and can drag the increments around to be sure to capture changing geometry.

There you have it! A complex surface specification of a rotor-stator cavity using the cavity drawing tool in Flownex!

A PADT Engineer in King Attiball’s Court – Chapter 6

There just is not enough engineer-focused fiction out there. Romance, Horror, Sci-Fi, Young Adult, Historical, Mystery, etc. They all do well, but they are rarely written for the engineers of the world.

Here at PADT, we are all about undoing such injustices. We decided to brainstorm a story about an engineer who does simulation and 3D Printing and ends up on an adventure. We hope they will find some mystery, some science fiction, and some horror. Maybe even a little romance. To develop the characters and the plot we all got on an MS Teams meeting and blocked it out. It was a lot of fun. That turned into an outline, that will turn into a chapter every month.

We hope you enjoy the result as much as we enjoyed dreaming the journey up.

It should be noted that every character in this story is completely made up. Sometimes we steal some names from real people as a shoutout to them, but that is about it. PADT does not have a basement or a fancy cluster in one. Everything is made up. Well, almost everything. We do have a stack of furniture in the back of shipping and receiving.


Chapter 1: Batch Submission | Chapter 2: New Friends | Chapter 3: Like an Owl
Chapter 4: Off to Sea | Chapter 5: City on the Nile

Chapter 6
Temple of Spies

Even though it was hard for Ash to break away from the spectacle of Giza, Alim and Ash headed to where the battery had been before the pirate attack, dodging the crewman as they readied the ship. It was not on the workbench where they had left it.

Ash’s biggest fear had come true – during the battle, the ship had made some abrupt turns, tilting the deck almost verticle to the water.

“I hope it didn’t fall overboard. You search that side,” she told Alim. “I’ll look over here.” Her heart sank as she looked in the stacked sails and supplies that surrounded the work area. She was frantic because her charging cable, and the only iPhone lightning connector that existed in the past, was attached to the clay jar.

She found no trace, not even some broken pottery. When she looked over her shoulder, Alim stood at the workbench, empty-handed.

The boat thudded against the dock, and for the first time on her journey, Ash felt hopeless. The majesty of Egypt stood before her in all its glory. But all she could think of was how she had lost touch with home.

“Well,” she said to herself in English, “I guess I am really stuck now.” She felt Alim’s hand on her shoulder, comforting her the only way he knew how.

“Who is your favorite trader? The master of the sea?” It was Duzi shouting from the far end of the ship.

Ash said to Alim, “I am in no mood for his bragging.”

Duzi kept on as he walked towards them. “Defeater of pirates, procurer of exotic spices, exporter of the greatest olive oil in the east, and importer of the finest rugs from the far west?”

He stopped behind them, and Ash said, “not now, Duzi.”

“But, I have one more claim to fame.”

Ash sighed. “Go ahead, what is it? Purveyor of succulent goat eyes? Seller of ice to Eskimos?”

“The first one is disgusting. And the second, I have no idea what ize or an esk-kee-mo is.”

“What then?”

“I, my skilled, beautiful, and mysterious foreign artificer, am also the finder of lost lightning jars.”

Ash spun around to look at him. He was standing next to the bench, with a toothy grin spread across his face. His arms were wrapped around the battery jar, the charging cable still attached to the two copper contacts. Relief surged through her. But at the same time, she could not look away from his infectious smile or stop thinking about how he had called her “HIS skilled, beautiful, and mysterious foreign artificer.”

She walked up to him, gently took the jar from his arms to place it on the bench, threw her arms around his neck, and kissed him all over his face. She found herself lingering a bit on his lips as he started to kiss her back. She lost herself in the feel of his strong body holding her.

The sounds of the dock, the crew moving about, and the blood rushing in her ears blocked out Verihbitt’s not-so-subtle vocal cues to get Duzi and Ash’s attention.

Frustrated with trying to be subtle, she yelled, “Duzi! The customs agent is waiting at the plank to speak to the shipmaster. I informed him that our captain fell overboard, and instead, we have an infatuated boy who is supposed to be in charge.”

The couple broke their embrace and flushed with embarrassment.

Ash said, “Um, thank you, Duzi, for finding my jar. It was very important to me.”

“We can all see how important it was to both of you,” said Verihbitt.

Duzi collected himself, flashed Ash that same smile, and said, “I should find your lost things more often.” Then he went in search of the customs agent.

Placing her backpack over one shoulder and gathering the battery in her arms, Ash followed Verihbitt and Alim off the ship in a daze. They stepped off the plank and onto the stone streets of Giza.

She took in the sites and sounds of the city and said, “I really do not know what came over me.”

Verihbitt laughed and tossed her long hair over her shoulder, “I know exactly what came over you. You need to build up resistance to the smile. He wields it as deftly as he does a spear.”

The oarsmen split into three groups. One in front of and another behind the travelers. A third group stayed on the ship. Duzi and Alim continued to talk to an official in long robes and a faded headdress. Ash saw a knowing look pass between the three men, followed by Alim passing a leather pouch to a slave next to the official. Once the bag was stashed away into the slave’s robes, they all bowed slightly to one another and parted. Duzi shouted an order to his men and joined the rest of the group to begin walking into the city.

The brightness of the painted walls and statues was almost overwhelming to Ash. Raised on pictures and video ruins with weathered stone, she had always pictured ancient cities as brown and gray. Although most of the homes and shops were made of mud bricks, plenty of markets and temples along their path assaulted the eyes with vivid coloring.

They walked up a small hill and turned into a courtyard to find a cluster of buildings that stood out because they were so different. Ash recognized the Phonecian architecture and the image of Baal over the entrance to the temple that stood in the center of the courtyard. A lush, green garden filled the space between the temple and the covered walkway that ran along the edges. Doorways to dark, and cooler rooms, peaked between the plants and columns. A single fountain gurgled off to one side.

Mnihh’dm climbed up on the low wall around the base of the fountain, filled his hands with water, and splashed his face.

He turned to the group and, with a flourish of his hand, pronounced, “welcome to this most sacred shrine to Baal, Lord of the Heavens, the southernmost home to the most divine and magnificent King Attiball, and his most trusted and loyal embassy to the mighty Pharos of Egypt. In that it is also very empty, I suspect that the King’s most honored caretaker is once again taking care of our most trustworthy ambassador, the King’s eighth son, at the most luxurious, discriminating, and expensive brothel in all of Giza. “

The group laughed a little nervously at Mnihh’dm’s irreverence.

“Come, Verihbitt, let us find and purify the women’s quarters for you and our foreign guest while Alim sweeps out the King’s suites and Takaa chases that rats from the barracks.”

Things were not as bad as the Mnihh’dm had implied. They had also found a group of Temple servants sleeping the afternoon away behind the altar. With their help, the quarters were squared away just before the sun began to set. Ash had even found a small workshop in the back corner that she commandeered. The battery was stored in a safe place, and she dispatched two of the temple servants to get her two baskets of whatever citrus they could find.

Ash kept looking for Duzi as they all hurried around the complex. He occasionally popped out into the courtyard to bark orders at his men. But he never glanced towards her. Doubt started to set in as she wondered if he had only responded to her affection out of reflex. And worse, that he now regretted his response.

When she ran out of things to do, she went looking for her friends. She found Verhibitt, Takaa, and Mnihh’dm sitting under a tree in the garden, drinking watered wine and snacking. Ash hesitated. She remembered what had happened that last time she had joined them in a courtyard, under a tree, for a light afternoon snack.

Takaa noticed her and the look of fear on her face. “Ash, please join us. Duzi’s soldiers are guarding the entrance and patrolling the walls. This meal will not be as exciting as the last one we had in a garden.”

Mnihh’dm held out a bowl of wine, and Verihbitt motioned to a spot on the bench next to her. Soon she was laughing with her friends and discussing their adventures since they had met. A witch trial, saving the King’s life, rescuing Verhibitt’s father, and escaping pirates. That was enough to put Duzi and his ignoring her out of her mind. The warmth of the food and wine mixed with the cool breeze blowing down the Nile, and she caught herself yawning.

Excusing herself, she headed off to her new bed. Laying there, she could hear both her friends and the oarsmen talking. She wondered if Duzi was with his troops, but she could not make out his voice across the courtyard. She fell asleep arguing with herself about what she should do first in the morning – talk to Duzi and figure out what was going on with them or charge up the battery and try and talk to Alex.

In the clear morning, contacting the future won out. As soon as Ash was washed, she headed to the workshop and rounded up a couple of the temple servants to squeeze the fruit their compatriots had scrounged up the previous night. Before long, she had a full pot of yellowish liquid. Ash sent them away and then slowly poured the juice into the battery. She then replaced the cloth around the copper contacts.

After testing the current with her tongue, she took a deep breath and plugged the connector into her phone.

She felt the phone vibrate in her hand. Ash was so excited she gave out a small squeak of joy. Then, a simple icon appeared on the screen showing an empty battery with a lightning bolt.

“Yes! It worked.”

She was not sure how long she paced back in forth in that small room. It seemed like hours, but the sun was still low in the sky when she tried to turn the phone on. The screen showed a time and five-percent battery.

Ash was so nervous it took her four times to put her PIN in. The warning about locking the phone terrified her, so she took her time on the fourth try and was rewarded with her home screen. One bar of signal showed in the upper right corner.

The messaging icon soon displayed the number five in its small red circle. Ash opened up the app and read messages from Alex.

Ash, are you there?

???

Checking in again, I hope your battery is not dead.

“Long one, just in case you get signal.Just to let you know, the FBI is involved now, as well as some other government people who don’t talk a lot. Like men-in-black looking government people. I’ve been “isolated” in the basement. They gave me a cot and bring food. I have some new friends that watch everything I do. Texting now from the bathroom stall. Sorry TMI. Oh, I can only send to you if I’m down in the basement near the fancy secret computer. I didn’t tell them what you told me. Let me know if that is OK. I did tell Harriet. She says time travel is not covered by short-term disability. And that she misses you and is very worried. They have told us to not shut down the quantum temporal server. I think they know it was involved in your disappearance, but they are telling me nothing. Your boss man Doug actually asked if your batch job was still running and if someone could take a look and try and get results from it. Yes, I know. I could not believe it either.”

“Nothing? It’s been another day here. We hope you are OK. Try and let us know how you are and if we should tell the g’ment.”

Ash stood looking at her phone for a long time. So much to take in. She started to type:

I’m still here. Had to build a battery from scratch. It worked! Don’t have much juice, fig n lit 😊 I’m safe. Won’t lie, it’s been dangerous. The ancient world is a ruthless place. I’ve made friends and we are helping each other. Ask H if I have enough vacation left to cover this? Lol. Seriously, tell her I miss her and have her tell my parents everything but to keep it to themselves. Until we figure out what happened, I don’t trust them. I watched too much x-files. Does that make me Skully and you Moulder? 😊 Battery going down, will try again tomorrow with more charge.

Ash reread the message and wanted to make some corrections but was worried her small charge would be gone. She pushed send. The phone made a whooshing sound and said sent.

She leaned her back against the bench and waited. Soon, three little dots appeared next to the “Alexes.”

So glad to hear from you!!!!! wOOt. Will do as you say. Please send any clues to help. Harriet is nice, but no hacker.

The real-time connection with the future sent adrenalin through Ash’s body. Her hands shook as she typed a response.

“Thx! Please send any info you have as text.”

OK

Before she could add more, the phone’s screen went black.

She went to find Alim and asked him to organize a steady stream of citrus fruit and squeezed juice, asking him to have the filled jugs left at the door to the workshop. Once the pitchers started showing up, she replenished the liquid in the battery. It seemed to her that the charging lasted about fifteen minutes. She resisted the temptation to send another message and instead left the phone off and concentrated on building up a full charge on her phone. Her brief time in the past had taught her that she might have to grab everything and run. She could not risk not having a full charge.

She worked like this, alone, taking solo walks around the courtyard between draining and filling the battery. The rest of her group seemed to be out doing other things, except Alim, who occasionally stopped in to check on her and offer help. When the sun set, he brought her an oil lamp and some dinner so she could keep going into the night.

“Ash, wake up. Ash.” Verihbitt was gently shaking her. “It is almost mid-day.”

Ash opened her eyes and saw wood. She had fallen asleep on the bench. She groaned in pain as she straightened her stiff back. With a start she remembered her phone and turned it on. While she waited for it to boot, she thanking Verihbitt and apologizing to her while she waited to see what charge she had.

The phone turned on and showed 97%. There were no new messages from Alex, so she turned it off and put the phone into her backpack’s pocket.

“Your magic clay tablet is working again?”

Ash said, “Yes, thanks to all of your help. It will be useful. I was so focused on fixing it that I let the day get away. Did I miss anything yesterday?”

“Let’s take a walk around the garden, and I’ll fill you in.”

A short time later, Verihbitt and Ash shared a sedan chair while Takaa and Mnihh’dm trotted behind the oarsmen who carried them. They were headed to the Temple of Montu, the Egyptian falcon god of war. While Ash had been charging batteries, the rest of the group had been out trying to find out more about the mysterious king that was terrorizing the eastern part of the sea. An Egyptian, recently returned from that part of the world, agreed to meet them there and fill them in on what he had seen.

When they arrived at the temple, Ash was once again so awed by what she saw that she was speechless. The tall, thin building had giant carved pillars at the entrance that depicted Montu’s consorts. Every wall was covered with colorful hieroglyphics. Ash wanted to stop one of the priests who scurried around the entrance and ask them to read the passages.

Verihbitt pulled on her arm and said, “Close your mouth and come inside.”

The massive interior was dimly lit by torches and a single shaft of light that came through the ceiling. More carved columns stretched on either side of the space. A huge statue of a falcon-headed man sat at the far end of the chamber. The three Phoenicians walked purposefully towards an altar at the base of the statue. Remembering to close her mouth, Ash scurried after.

A man in elaborate robes stood to the side of the altar, gazing up at the statue. When the group got close, he turned towards them and asked, “did you bring the sacrifice?”

Mnihh’dm stepped forward and deposited a wrapped bundle on the altar.

“We have brought a sacred cat to honor the god Montu.”

The package was bigger than any cat Ash had seen, and she thought she heard the sound of clinking coins when Mnihh’dm placed it on the altar. The robed man picked it up to gauge its weight, and Ash clearly heard the coins. Once her eyes adjusted to the gloomy interior, Ash noticed more robed men milling about all around them, their faces hidden in large hoods.

The man bowed and said, “The god will be pleased.” He spoke something in what must have been Egyptian towards a dark alcove in the side of the chamber, and a thin man in a tattered tunic stumbled forward.

The man fell to his knees and began to mumble a sing-song chant towards the statue.

“You can pray later.” Said the robed man, who Ash assumed must be a priest. “Now, you need to tell these people what you saw. In the language of the traders.”

The prostrate man rose to his feet, and in broken Phoenician, began to talk.

“We were five weeks in voyage, traveling with a wealthy tax collector. He wanted to show his wife the west. Past Tripoli, we were. We see the black towns.”

He stopped and dropped to his knees again, and began to pray. Ash could sense the terror in his voice, even though she did not know the language he spoke.

The priest pulled the man back to his feet and shook him.

“After many places we find black, we turn back to Tripoli. We see it there and then the thunder brought the sun to us and flames. Death. I jump in the sea. Grab piece of wood. Wake up on shore near Tripoli. Our ship gone.”

Verihbitt stood in front of the man and gently grabbed his shoulders. She asked, “What did you see before the thunder, before the sun came?”

The man looked away. He began to shake and cry. Finally, he said, “We see the largest ship we ever see. It long and –“

One of the hooded priests was running towards the man, a large club raised above his head. Before Ash or any of her companions could gather what was going on, he brought the club down and the man’s head. Brains and blood spattered over the altar and the base of the statue.

Ash heard a loud banging and turned just in time to see the large bronze doors at the entrance to the chamber slam shut. Several groups of hooded priests slowly moved towards them.

Takaa shouted, “Behind me.”

Ash muttered, “not again” in English, and dashed to get behind the bodyguard. Both he and Mnihh’dm pulled long bronze knives from beneath their cloaks. Verihbitt leaped up onto the statue and pulled a spear from the stone hands of the god.

They slowly backed to the side of the statue, a hieroglyphics-covered wall behind them. The priests continued to move forward. Each one carried a large club like the one used to murder the man they had been questioning.

Their guards were outside, locked outside of the bronze doors. Ash realized, with a cold hard shiver, that they were trapped.

Her three friends took a defensive stance in front of her as she tried to reason out some solution. She thought about taking her phone out to text a message to Alex and her parents. Then she remembered the flash on the phone and how the people in the market had been terrified by the bright light. She quickly took the phone from her backpack pocket and turned it on. The priests got closer, forming a semicircle of at least a dozen men.

The phone turned on and she hit the photo icon, turned the flash on, and snapped a picture of the men approaching them.

They shouted in fear and covered their eyes, shouting the Phoenician word for bright lightening. Noticing their distraction, Verihbitt stepped forward and smashed an oil torch hanging from the wall, sending flames towards the priests. That stopped enough for them for Mnihh’dm and Takaa to jump forward, slicing and stabbing their long knives. Ash flashed the camera again, and Verihbitt joined the two men to hack and slash at their foes. Before she could push the button for a third flash, all of the priests were fleeing, bleeding on the floor, or screaming in agony from the burning oil that covered them.

Verihbitt leaned on the sacred spear she had borrowed from the god and said, “These are no Egyptian priests of Montu. They were speaking fluent Phoenician.”

Takaa said, “You are right, and look.” He bent to pull the robes off the chest of one of the dead priests. She reached down and pulled a necklace of the corpse. “They are all wearing these.”

The necklace had a large bronze disk that was clearly a stylized sun. Below the shiny disk, a half-dozen lightning bots shot from the sun in different directions. Ash had never seen anything like it in any of the Phoenecian jewelry she had studied.

Verihbitt took the necklace and looked at it more closely. She turned it over, looking for writing or any additional marks. She handed it back to Takaa. Then she walked to the base of the statue of Montu and gently placed the spear in its lap.

“Most honored Montu,” she said, “I am sorry we desecrated your shrine. But these men are not your priests. They are adherents to a cult that worships Reshef and Shapash. A cult that I thought my uncle had exterminated. Thank you for protecting us here in your shrine and for the use of your spear. We ask for your protection and guidance as we travel further west.” She then backed away from the statue, head bowed.

Verihbitt turned around when she reached the altar, grabbed the oversized coin-filled cat, and said to the group, “I think we should take this sacrifice with us to Tripoli. It might come in handy.”

– To Be Continued –

Please subscribe to our newsletter, so you will know when the next installment, “Three Days in Tripoli,” is released, wherein, after a brief stay in Egypt to gather supplies, Ash and friends sail westward again to the ancient Phoenician city of Tripoli (well, it ended up being called Tripoli later) where they hope to learn more about the mysterious king, his cult, and the superweapon he was using to burn cities to the ground.

Phoenician Cities - Phoenicia

Welcome to a New Era in Electronics Reliability Simulation

Simulation itself is no longer a new concept in engineering, but individual fields, applications, and physics are continually improved upon and integrated into the toolbox that is an engineer’s arsenal. Many times, these are incremental additions to a particular solver’s capabilities or a more specialized method of post processing, however this can also occasionally be present through new cross-connections between separate tools or even an entirely new piece of software. As a result of all this, Ansys has now reached critical mass for its solution space surrounding Electronics Reliability. That is, we can essentially approach an electronics reliability problem from any major physics perspective that we like.

So, what is Electronics Reliability and what physics am I referring to? Great question, and I’m glad you asked – I’d like to run through some examples of each physics and their typical use-case / importance, as well as where Ansys fits in. Of course, real life is a convoluted Multiphysics problem in most cases, so having the capability to accommodate and link many different physics together is also an important piece of this puzzle.

Running down the list, we should perhaps start with the most obvious category given the name – Electrical Reliability. In a broad sense, this encompasses all things related to electromagnetic fields as they pertain to transmission of both power and signals. While the electrical side of this topic is not typically in my wheelhouse, it is relatively straightforward to understand the basics around a couple key concepts, Power Integrity and Signal Integrity.

Power integrity, as its name suggests, is the idea that we need to maintain certain standards of quality for the electrical power in a device/board/system. While some kinds of electronics are robust enough that they will continue to function even under large variations in supplied voltage or current, there are also many that rely on extremely regular power supplies that only vary above certain limits or within narrow bounds. Even if we’re looking at a single PCB (as in the image below), in today’s technological environment it will no doubt have electrical traces mapped all throughout it as well as multiple devices present that operate under their own specified electrical conditions.

Figure 1: An example PCB with complex trace and via layouts, courtesy of Ansys

If we were determined to do so, we could certainly measure trace lengths, widths, thicknesses, etc., and make some educated guesses for the resulting voltage drops to individual components. However, considerably more effort would need to be made to account for bends, corners, or variable widths, and that would still completely neglect any environmental effects or potential interactions between traces. It is much better to be able to represent and solve for the entire geometry at once using a dedicated field solver – this is where Ansys SIwave or Ansys HFSS typically come in, giving us the flexibility to accurately determine the electrical reliability, whether we’re talking about AC or DC power sources.

Signal integrity is very much related, except that “signals” in this context often involve different pathways, less energy, and a different set of regulations and tolerances. Common applications involve Chip-signal modeling and DDRx virtual compliance – these have to do with not only the previous general concerns regarding stability and reliability, but also adherence to specific standards (JEDEC) through virtual compliance tests. After all, inductive electromagnetic effects can still occur over nonconductive gaps, and this can be a significant source of noise and instability in cases where conductive paths (like board traces or external connections) cross or run very near each other.

Figure 2: Example use-cases in virtual compliance testing, courtesy of Ansys

Whether we are looking at timings between components, transition times, jitter, or even just noise, HFSS and SIWave can both play roles here. In either case, being able to use a simulation environment to confirm that a certain design will or will not meet certain standards can provide invaluable feedback to the design process.

Other relevant topics to Electrical Reliability may include Electromagnetic Interference (EMI) analysis, antenna performance, and Electrostatic Discharge (ESD) analysis. While I will not expand on these in great detail here, I think it is enough to realize that an excellent electrical design (such as for an antenna) requires some awareness of the operational environment. For instance, we might want to ensure that our chosen or designed component will adequately function while in the presence of some radiation environment, or maybe we would like to test the effectiveness of the environmental shielding on a region of our board. Maybe, there is some concern about the propagation of an ESD through a PCB, and we would like to see how vulnerable certain components are. Ansys tools provide us the capabilities needed to do all of this.

The second area of primary interest is Thermal Reliability, as just about anyone who has worked with or even used electronics knows, they generate some amount of heat while in use. Of course, the quantity, density, and distribution of that heat can vary tremendously depending on the exact device or system under question, but this heat will ultimately result in a rise in temperature somewhere. The point of thermal reliability basically boils down to realizing that the performance and function of many electrical components depends on their temperature. Whether it is simply a matter of accounting for a change in electrical conductivity as temperature rises or a hard limit of functionality for a particular transistor at 150 °C, acknowledging and accounting for these thermal effects is critical when considering electronics reliability. This is a problem with several potential solutions depending on the scale of interest, but generally we cover the package/chip, board, and full system levels. For the component/chip level, a designer will often want to provide some package level specs for OEMs so that a component can be properly scoped in a larger design. Ansys Icepak has toolkits available to help with this process; whether it is simplifying a 3D package down to a detailed network thermal model or identifying the most critical hot spot within a package based on a particular heat distribution. Typically, network models are generated through temperature measurements taken from a sample in a standardized JEDEC test chamber, but Icepak can assist through automatically generating these test environments, as below, and then using simulation results to extract well defined JB and JC values for the package under test.

Figure 3: Automatically generated JEDEC test chambers created by Ansys Icepak, courtesy of Ansys

On the PCB level of detail, we are likely interested in how heat moves across the entire board from component to component or out to the environment. Ansys Icepak lets us read in a detailed ECAD description for said PCB and process its trace and via definitions into an accurate thermal conductivity map that will improve our simulation accuracy. After all, two boards with identical sizing and different copper trace layouts may conduct heat very differently from each other.

Figure 4: Converting ECAD information into thermal conductivity maps using Ansys Icepak, courtesy of Ansys

On the system level of thermal reliability, we are likely looking at the effectiveness of a particular cooling solution on our electronic design. Icepak makes it easy to include the effects of a heat exchanger (like a coldplate) without having to explicitly model its computationally expensive geometry by using a flow network model. Also, many of today’s electronics are expected to constantly run right up against their limit and are kept within thermal spec by using software to throttle their input power in conjunction with an existing cooling strategy. We can use Icepak to implement and test these dynamic thermal management algorithms so that we can track and evaluate their performance across a range of environmental conditions.

The next topic that we should consider is that of Mechanical Reliability. Mechanical concepts tend to be a little more intuitive and relatable due to their more hands-on nature than the other two, though the exact details behind the cause and significance of stresses in materials is of course more involved. In the most general sense, stress is a result of applying force to an object. If this stress is high compared to what is allowed by a material, then bad things tend to happen – like permanent deformation or fracture. For electronic devices consisting of many materials, small structures, and particularly delicate components, we have once again surpassed what can be reasonably accomplished with hand calculations. Whether we are looking at an individual package, the integrity of an entire PCB, or the stability that a rigid housing will provide to a set of PCBs, Ansys has a solution. We might use Ansys Mechanical to look at manufacturing allowances for the permissible force used while mounting a complicated leaded component onto a board, as seen below. Or maybe, we will use mechanical simulation to find the optimal positioning of leads on a new package such that its natural vibrational frequencies are outside normal ambient conditions.

Figure 5: A surface component with discretely modeled leads, courtesy of Ansys

At the PCB level, we face many of the same detail-oriented challenges around representing traces and vias that have been mentioned for the electrical applications. They may not be quite as critical and more easily approximated in some ways, but that does not change the fact that copper traces are mechanically quite different from the resin composites often used as the substrate (like FR-4). Ansys tools like Sherlock provide best in class PCB modeling on this front, allowing us to directly bring in ECAD models with full trace and component detail, and then model them mechanically at several different levels depending on the exact need. Automating a materials property averaging scheme based on the local density of traces may be sufficient if we are looking at the general bending behavior of a board, but we can take it to the next level by explicitly modeling traces as “reinforcement” elements. This brings us to the level of detail where we can much more reliably look at the stresses present in individual traces, such that we can make good design decisions to reduce the risk of traces peeling or delaminating from the surface.

Figure 6: Example trace mapping workflow and methods, courtesy of Ansys

Beyond just looking at possible improvements in the design process, we can also make use of Ansys tools like LS-DYNA or Mechanical to replicate testing or accident conditions that an existing design could be subjected to. As a real-world example, many of us are all too familiar with the occasional consequences of accidentally dropping our smart phones – Ansys is used to test designs against these kind of shock events, where impact against a hard surface can result in high stresses in key locations. This helps us understand where to reinforce a design to protect against the worst damage or even what angle of impact is most likely to cause an operational failure.

As the finale for all of this, I come back to the first comment of reality being a complex Multiphysics problem. Many of the previous topics are not truly isolated to their respective physics (as much as we often simplify them as such), and this is one of the big ways in which the Ansys ecosystem shines: Comprehensive Multiphysics. For the topic of thermal reliability, I simply stated that electronics give off heat. This may be obvious, but that heat is not just a magical result of the device being turned on but is instead a physical and calculable result of the actual electrical behavior. Indeed, this the exact kind of result that we can extract from one of the relevant electronics tools. An HFSS solution will provide us with not only the electrical performance of an antenna but also the three-dimensional distribution of heat that is consequently produced. Ansys lets us very easily feed this information into an Icepak simulation, which then has the ability to give us far more accurate results than a typical uniform heat load assumption provides.

Figure 7: Coupled electrical-thermal simulation between HFSS and Icepak, courtesy of Ansys

If we find that our temperatures are particularly high, we might then decide to bring these results back into HFSS to locally change material properties as a function of temperature to get an even more accurate set of electrical results. It could be that this results in an appreciable shift in our antenna’s frequency, or perhaps the efficiency has decreased, and aspects of the design need to be revisited. These are some of the things that we would likely miss without a comprehensive Multiphysics environment.

On a more mechanical side, the effects on stress and strain from thermal conditions are very well known and understood at this point, but there is no reason we could not use Ansys to bring the electrical alongside this established thermal-mechanical behavior. After all, what is a better representation of the real physics involved than using SIwave or HFSS to model the electrical behavior of a PCB, bringing those result into an Icepak simulation as a heat load to test the performance of a cooling loop or heat sink, and then using at least some of those thermal results to look at stresses through not only a PCB as a whole but also individual traces? Not a whole lot at this moment in time, I would say.

The extension that we can make on these examples, is that they have by and large been representative cases of how an electronics device responds to a particular event or condition and judging its reliability metrics based on that set of results, however many physics might be involved. There is one more piece of the puzzle we have access to that also interweaves itself throughout the Multiphysics domain and that is Reliability Physics. This is mostly relevant to us in electronics reliability for considering how different events, or even just a repetition of the same event, can stack together and accumulate to contribute towards some failure in the future. An easy example of this is a plastic hinge or clip that you might find on any number of inexpensive products – flexing a thin piece of plastic like in these hinges can provide a very convenient method of motion for quite some time, but that hinge will gradually accumulate damage until it inevitably cracks and fails. Every connection within a PCB is susceptible to this same kind of behavior, whether it is the laminations of the PCB itself, the components soldered to the surface, or even the individual leads on a component. If our PCB is mounted on the control board of a bus, satellite, or boat, there will be some vibrations and thermal cycles associated with its life. A single one of these events may be of much smaller magnitude and seemingly negligible compared to something dramatic like a drop test, and yet they can still add up to the point of being significant over a period of months or years.

This is exactly the kind of thing that Ansys Sherlock proves invaluable for: letting us define and track the effect of events that may occur over a PCB’s entire lifecycle. Many of these will revolve around mechanical concepts of fatigue accumulating as a result of material stresses, but it is still important to consider the potential Multiphysics origins of stress. Different simulations will be required for each of mechanical bending during assembly, vibration during transport, and thermal cycling during operation, yet each of these contributes towards the final objective of electronics reliability. Sherlock will bring each of these and more together in a clear description of which components on a board are most likely to fail, how likely they are to fail as a function of time, and which life events are the most impactful.

Figure 8: Example failure predictions over the life cycle of a PCB using Ansys Sherlock, courtesy of Ansys

Really, what all of this comes down to is that when we design and create products, we generally want to make sure that they function in the way that we intend them to. This might be due to a personal pride in our profession or even just the desire to maximize profit through minimizing the costs associated with a component failure, however at the end it just makes sense to anticipate and try to prevent the failures that might occur under normal operating conditions.

For complex problems like electronics devices, there are many physics all intimately tied together in the consideration of overall reliability, but the Ansys ecosystem of tools allows us to approach these problems in a realistic way. Whether we’re looking at the electrical reliability of a circuit or antenna, the thermal performance of a cooling solution or algorithm, or the mechanical resilience of a PCB mounted on a bracket, Ansys provides a path forward.

If you have any questions or would like to learn more, please contact us at info@padtinc.com or visit www.padtinc.com.

Introducing Ansys Rocky – Webinar

PADT is excited to share more information on one of the latest Ansys acquisitions, Rocky DEM.

Rocky is a powerful 3D Discrete Element Modeling (DEM) Particle Simulation Software that quickly and accurately simulates the flow behavior of bulk materials with complex particle shapes and size distributions, for typical applications such as conveyor chutes, mills, mixers, and other materials handling equipment.

Rocky is fully integrated with the Ansys Workbench suite of products, providing engineers with the ability to perform coupled analysis of particles simulation together with other physics such as structural and fluids. 

Such coupling can be performed using both 1-way and 2-way approaches, depending upon the nature of the problem to be solved. When Rocky is coupled with Ansys Mechanical software, engineers can evaluate the tension stresses and forces generated by granular matter as it interacts with materials handling equipment, such as transfer chutes and conveyor belts.

Join PADT’s Senior CFD Engineer and Rocky expert Tom Chadwick for a look at what this tool is all about, as well as how it operates in a variety of industries, such as:

  • Food & Beverage
  • Agricultural Equipment
  • Medical Devices
  • And More

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