## Topological Optimization in ANSYS 18.1 – Motorcycle Component Example

We’ve discussed topological optimization in this space before, notably here:

If you’re not familiar with topological or topology optimization, a simple description is that we are using the physics of the problem combined with the finite element computational method to decide what the optimal shape is for a given design space and set of loads and constraints. Typically our goal is to maximize stiffness while reducing weight. We may also be trying to keep maximum stress below a certain value. Frequencies can come into play as well by linking a modal analysis to a topology optimization.

Why is topology optimization important? First, it produces shapes which may be more optimal than we could determine by engineering intuition coupled with trial and error. Second, with the rise of additive manufacturing, it is now much easier and more practical to produce the often complex and organic looking shapes which come out of a topological optimization.

ANSYS, Inc. has really upped the game when it comes to utilizing topology optimization. Starting with version 18.0, topo opt is built in functionality within ANSYS. If you already know ANSYS Mechanical, you already know the tool that’s used. The ANSYS capability uses the proven ANSYS solvers, including HPC capability for efficient solves. Another huge plus is the fact that SpaceClaim is linked right in to the process, allowing us to much more easily make the optimized mesh shape produced by a topological optimization into a more CAD representation set for use in validation simulations, 3D printing, or traditional manufacturing.

The intent of this blog is to show the current process in ANSYS version 18.1 using a simple example of an idealized motorcycle front fork bracket optimization. We don’t claim to be experts on motorcycle design, but we do want to showcase what the technology can do with a simple example. We start with a ‘blob’ or envelope for the geometry of our design space, then perform an optimization based on an assumed set of loads the system will experience. Next we convert the optimized mesh information into solid geometry using ANSYS SpaceClaim, and then perform a validation study on the optimized geometry.

Here we show our starting point – an idealized motorcycle fork with a fairly large blob of geometry. The intent is to let ANSYS come up with an optimal shape for the bracket connecting the two sides of the fork.

The first step of the simulation in this case is a traditional Static Structural simulation within ANSYS Workbench. The starting point for the geometry was ANSYS SpaceClaim, but the initial geometry could have come from any geometry source that ANSYS can read in, meaning most CAD systems as well as Parasolid, SAT, and STEP neutral file formats.
A single set of loads can be used, or multiple load cases can be defined. That’s what we did here, to simulate various sets of loads that the fork assembly might experience during optimization. All or a portion of the load cases can be utilized in the topological optimization, and weighting factors can be used on each set of loads if needed.
Here we see the workflow in the ANSYS Workbench Project Schematic:

Block A is the standard static structural analysis on the original, starting geometry. This includes all load cases needed to describe the operating environment. Block B is the actual topological optimization. Block C is a validation study, performed on the optimized geometry. This step is needed to ensure that the optimized shape still meets our design intent.

Within the topology optimization, we set our objective. He we choose minimizing compliance, which is a standard terminology in topology optimization and we can think of it as the inverse which is maximizing stiffness.

In the static structural analysis, 7 load cases were used to describe different loading situations on the motorcycle fork, and here all have been used in the optimization.
Further, we defined a response constraint, which in this example is to reduce mass (actually retain 15% of the mass):

Another quantity that’s often useful to specify is a minimum member constraint. That will keep the topology optimization from making regions that are too small to 3D print or otherwise manufacture. Here we have specified a minimum member size of 0.3 inches:

Since the topological optimization solution uses the same ANSYS solvers for the finite element solution as a normal solution, we can leverage high performance computing (distributed solvers, typically) to speed up the solution process. Multiple iterations are needed to converge on the topology optimization, so realize that the topo opt process is going to be more computationally expensive than a normal solution.

Once the optimization is complete, we can view the shape the topo opt method has obtained:

Notice that only a portion of the original model has been affected. ANSYS allows us to specify which regions of the model are to be considered for optimization, and which are to be excluded.

Now that we have a shape that looks promising, we still need to perform a validation step, in which we rerun our static simulation with the loads and constraints we expect the fork assembly to experience. To do that, we really want a ‘CAD’ model of the optimized shape. The images shown above show the mesh information that results from the topo opt solution. What we need to do next is leverage the ANSYS SpaceClaim geometry tool to create a solid model from the optimized shape.
A simple beauty in the ANSYS process is that with just a couple of clicks we proceed from Block B to Block C in the Workbench project schematic, and can then work with the optimized shape in SpaceClaim.

As you can see in the above image, SpaceClaim automatically has the original geometry as well as the new, optimized shape. We can do as much or as little to the optimized shape as we need, from smoothing and simplification to adding manufacturing features such as holes, bosses, etc. In this case we simply shrink wrapped it as-is.
Continuing with the validation step, the geometry from SpaceClaim automatically opens in the Mechanical window and we can then re-apply the needed loads and constraints and then solve to determine if the optimized shape truly meets our design objectives. If not, we can make some tweaks and run again.

The above image shows a result plot from the validation step. The geometry efficiently comes through SpaceClaim from the optimization step to the validation step. The needed tools are all nicely contained within ANSYS.

Hopefully this has given you an idea of what can be done with topology optimization in ANSYS as well as how it’s done. Again, if you already know ANSYS Mechanical, you already know the bulk of how to do this. If not, then perhaps what you have seen here will spark a craving to learn. We can’t wait to see what you create.

## Distributed ANSYS 18.1 with the SP-5 Benchmark using an INTEL 1.6TB NVMe

I recently had a chance to run a series of benchmarks on one of our latest CUBE numerical simulation workstations. I was amazed by the impressive benchmark numbers and wanted to share with you the details for the SP-5 benchmark using ANSYS 18.1. Hopefully this information will help you make the best decision the next time you need to upgrade your numerical simulation C Drive from whatever to now is the time to buy a Non-Volitile Memory Express drive. Total speedup using identical CUBE hardware, except for the INTEL DC P3700 NVMe drive @32 Cores is a 1.19x speedup!

• Time Spent Computing Solution ANSYS SP-5 Benchmark
• 161.7 seconds vs. 135.6 second
• ANSYS 17.1 & ANSYS 18.1 Benchmarks

The link below is to a great article that I think will catch you up to speed regarding NVMe, PCIe and SSD Technology.

HDD Magazine hints NVME is coming, I say NVMe is already here…

# CUBE w32iP Specifications (July 2017)

• CUBE Mid-Tower Super Quiet Chassis (900W PS)
• CPU: 32 INTEL Cores – 2 x INTEL e5-2697A V4 32c@2.6GHz/3.6GHz Turbo
• OS: INTEL NVMe – 1 x 1.6TB INTEL Enterprise Class SSD
• Mid-Term Storage: – 1 x 10TB Enterprise Class SATA 6Gbp/s, 256M, Helium sealed
• RAM: 256GB DDR4-2400MHz LRDIMM RAM
• GRAPHICS: NVIDIA QUADRO P6000 (24GB GDDR5X RAM)
• MEDIA: DVD-RW/Audio 7.1 HD
• Windows 10 Professional

## Just how much faster the INTEL NVME drive performs over previously run ANSYS Benchmarks?

### Check out the data for yourself:

• ANSYS Benchmark Test Case Information.
• ANSYS HPC Licensing Packs required for this benchmark
• I used (2) HPC Packs to unlock all 32 cores.
• 1.19x Total Speedup!
• Designed, tested and configured within your budget. We are happy to help and to  listen to your specific needs.

# ANSYS SP-5 Benchmark Details

#### BGA (V18sp-5)

Analysis Type Static Nonlinear Structural
Number of Degrees of Freedom 6,000,000
Equation Solver Sparse
Matrix Symmetric
 July 2017 TIME SPENT COMPUTING SOLUTION TOTAL CPU TIME FOR MAIN THREAD ELAPSED TIME CUBE w32iP CUEB w32iP CUBE w32iP # of Cores CUBE w32iP CUBE w32iP CUBE w32iP 2 1034.3 1073.7 1076 4 594.7 630.3 633 6 431.5 465.7 472 8 333.4 367.9 377 10 268.7 302.6 316 12 243.6 276.5 287 14 223 256.2 264 16 186.8 219.3 227 18 180 212.4 226 20 174.4 207.4 220 22 164.5 197.4 209 24 155.6 188.2 199 26 147.1 179.2 193 28 146.4 178.2 190 30 140.8 168.5 196 31 140.4 164 196 32 135.6 158.1 182 WO/GPU Acceleration WO/GPU Acceleration WO/GPU Acceleration July 2017, drjm, PADT, Inc.

CUBE W32iP SP-5 Benchmark Graph

## Webinar: Additive Manufacturing & Simulation Driven Design, A Competitive Edge in Aerospace

PADT recently hosted the Aerospace & Defence Form, Arizona Chapter for a talk and a tour. The talk was on “Additive Manufacturing & Simulation Driven Design, A Competitive Edge in Aerospace” and it was very well received.  So well in fact, that we decided it would be good to go ahead and record it and share it. So here it is:

Aerospace engineering has changed in the past decades and the tools and process that are used need to change as well. In this presentation we talk about how Simulation and 3D Printing can be used across the product development process to gain a competitive advantage.  In this webinar PADT shares our experience in apply both critical technologies to aerospace. We talk about what has changed in the industry and why Simulation and Additive Manufacturing are so important to meeting the new challenges. We then go through five trends in each industry and keys to being successful with each trend.

## Video Tips – Two-way connection between Solidworks and ANSYS HFSS

This video will show you how you can set up a two-way connection between Solidworks and ANSYS HFSS so you can modify dimensions as you are iterating through designs from within HFSS itself. This prevents the need for creating several different CAD model iterations within Solidworks and allows a more seamless workflow.  Note that this process also works for the other ANSYS Electromagnetic tools such as ANSYS Maxwell.

## Importing and Splitting Solid Models for ANSYS HFSS 18.0

Importing solid 3D Mechanical CAD (or MCAD) models into ANSYS HFSS has always been and remains to be a fairly simple process. After opening ANSYS Electronics Desktop and creating an HFSS design, from the menu bar, select Modeler > Import. A dialog box will open to navigate to and directly open the model.

The CAD will automatically be translated and loaded into the HFSS 3D Modeler. If the geometry is correct and does not require any editing, the import process is complete and analysis can begin! However, if there are any errors with the geometry, there is excessive or invalid detail, or if it’s not organized into separate bodies conducive for electromagnetic analysis, you may soon realize that the editing capability is limited to scaling, reorienting, or Boolean operations. This approach can be particularly troublesome when portions of the model (or all of the model) which consist of different materials are not split into different objects. For example, notice the outer conductor, inner conductor, and dielectric of the imported SMA below are all one solid object.

[1] First, after opening ANSYS SpaceClaim, the step file can be imported through the menu File > Open or by simply dragging and dropping the file into the SCDM window. [2] To separate the dielectric from the outer conductor, select Design > Intersect > Split Body. [3] Click and hold the center mouse button to rotate the model so the boundary between the dielectric and outer conductor is visible. Hold the Ctrl key and click the center mouse button to pan, and use the center mouse scroll to zoom in and out. Finally, press ‘z’ on the keyboard to fit the view window. [4] When positioned, click on the object to split (in this case it is the entire model). [5] Then, click on the face which defines the boundary between the dielectric and outer conductor. [6] Finally, press the Esc key. The first split is done!

Repeat the Split Body process to separate the center conductor from the dielectric. Notice under the structure tree that there are now three separate objects.

The split body function is also useful to simplify a structure for analysis. For example, the female side of the SMA could be simplified as a solid center conductor. [1] Reposition the connector to view the female side. [2]-[3] Control the visibility of each body with the object’s checkbox in the structure tree. [4] Measure the length of the female side by pressing the letter ‘e’ on the keyboard and selecting the top edge (note the line length of 2.95mm for later). [5] Then, repeat the Split Body process to split the center conductor at the boundary between the male and female sides. [6]-[7] However, rather than pressing the Esc key, click on the female receiver to automatically remove the body.

[1] To extend the center pin to its original length, select Design > Edit > Pull. [2] Click on the face where the female side was originally attached and select the Up To option. [3] Type in the previously measured length of 2.95mm. [4] Finally, press Enter (press Esc 3x to exit the Pull command).

Repeat the Split Body and Pull processes until the model has been divided into different bodies for each material type and is sufficiently simplified.

Once the model is ready, select File > Save As to save the geometry as the preferred format. Perhaps the most familiar approach to HFSS users would be to save the new model as a STEP file, then to import the model into HFSS as described in the first paragraph.

## Overset Meshing in ANSYS Fluent 18.0

One of the tough challenges in creating meshes for CFD simulations is the requirement to create a mesh that works with very different geometry. With Overset meshing you can create the ideal mesh for each piece of geometry in your model, and let them overlap where they touch and the program handles the calculations at those boundaries. All of this is handled simply in the ANSYS Workbench interface and then combined in ANSYS FLUENT.

## Secant or Instantaneous CTE? Understanding Thermal Expansion Modeling ANSYS Mechanical

One of the more common questions we get on thermal expansion simulations in tech support for ANSYS Mechanical and ANSYS Mechanical APDL revolve around how the Coefficient of Thermal Expansion, or CTE. This comes in to play if the CTE of the material you are modeling is set up to change with the temperature of that material.

This detailed presentation goes in to explaining what the differences are between the Secant and Instantaneous methods, how to convert between them, and dealing with extrapolating coeficients beyond temperatures for which you have data.

## Getting to Know PADT: Flownex Sales and Support

This is the second installment in our review of all the different products and services PADT offers our customers. As we add more, they will be available here.  As always, if you have any questions don’t hesitate to reach out to info@padtinc.com or give us a call at 1-800-293-PADT.

The PADT sales and support team focused on simulation solutions is best known for our work with the full ANSYS product suite.  What a lot of people don’t know is that we also represent a fantastic simulation tool called Flownex. Flownex is a system level 1-D program that is designed from the ground up to model thermal-fluid systems.

### What does Flownex Do?

Flownex Simulation Environment is an interactive software program that allows users to model systems to understand how fluids (gas and/or liquid) flow and how heat is transferred in that same system due to that flow.  the way it works is you create a network of components that are connected together as a system.  The heat and fluid transfer within and between each node is calculated over time, giving a very accurate, and fast,  representation of the system’s behavior.

As a system simulation tool, it is fast, it is easy to build and change, and it runs in real time or even faster.  This allows users to drive the design of their entire system through simulation.

Need to know what size pump you need, use Flownex.  Want to know if you heat exchanger is exchanging enough heat for every situation, use Flownex.  Tasked with making sure your nuclear reactor will stay cool in all operating conditions, use Flownex.   Making sure you have optimized the performance of your combustion nozzles, use Flownex.  Time to design your turbine engine cooling network, use Flownex. Required to verify that your mine ventilation and fire suppression system will work, use Flownex. The applications go on and on.

### Why is Flownex so Much Better than other System Thermal-Fluid Modeling Solutions?

There are a lot of solutions for modeling thermal-fluid systems. We have found that the vast majority of companies use simple spreadsheets or home-grown tools. There are also a lot of commercial solutions out there. Flownex stands out for five key reasons:

1. Breadth and depth of capability
Flownex boasts components, the objects you link together in your network, that spread across physics and applications.  Whereas most tools will focus on one industry, Flownex is a general purpose tool that supports far more situations.  For depth they have taken the time over the years to not just have simple models.  Each component has sophisticated equations that govern its behavior and user defined parameters that allow for very accurate modeling.
2. Developed by hard core users
Flownex started life as an internal code to support consulting engineers. Experienced engineering software programmers worked with those consultants day-in and day-out to develop the tools that were needed to solve real world problems.  This is the reason why when users ask “What I really need to do to solve my problem is such-and-such, can Flownex do that?” we can usually answer “Yes, and here are the options to make it even more accurate.”
3. Customization and Integration
As powerful and in-depth as Flownex is, there is no way to capture every situation for every user.  Nor does the program do everything. That is why it is so open and so easy to customize and integrate. As an example, may customers have very specific thermal-pressure-velocity models that they use for their specific components. Models that they developed after years if not decades of testing. Not a problem, that behavior can be easily added to Flownex.  If a customer even has their own software or a 3rd party tool they need to use, it is pretty easy to integrate it right into your Flownex system model.Very common tools are already integrated. The most common connection is Matlab/Simulink.  At PADT we often connect Excel models from customers into our Systems  for consulting.  It is also integrated into ANSYS Mechanical.
4. Nuclear Quality Standards
Flownex came in to its own as a tool used to model the fluid system in and around Nuclear Reactors.  So it had to meet very rigorous quality standards, if not the most stringent they are pretty close. This forced to tool to be very robust, accurate, and well documented. And the rest of us can take advantage of that intense quality requirement to meet and exceed the needs of pretty much every industry.  We can tell you after using it for our own consulting projects and after talking to other users, this code is solid.
5. Ease of Use
Some people will read the advantages above and think that this is fantastic, but that much capability and flexibility must make it difficult to use. Nothing could be further from the truth.  Maybe its because the most demanding users are down the hallway and can come and harangue the developers. Or it could be that their initial development goal of keeping ease of use without giving up on functionality was actually followed.  Regardless of why, this simulation tool is amazingly simple and intuitive.  From building the model to reviewing results to customization, everything is easy to learn, remember, and user.  To be honest, it is actually fun to use. Not something a lot of simulation engineers say.

### Why does buying and getting support from PADT for Flownex make a Difference?

The answer to this question is fairly simple: PADT’ simulation team is made up of very experienced users who have to apply this technology to our own internal projects as well as to consulting jobs.  We know this tool and we also work closely with the developers at Flownex.  As with our ANSYS products, we don’t just work on knowing how to use the tool, we put time in to understand the theory behind everything as well as the practical real world industry application.

When you call for support, odds are the engineer who answers is actually suing Flownex on a customer’s system.  We also have the infrastructure and size in place to make sure we have the resources to provide that support.  Investing in a new simulation tool can generate needs for training, customization, and integration; not to mention traditional technical support. PADT partners with our customers to make sure they get the greatest value form their simulation software investment.

Our team is ready and waiting to answer your questihttp://www.flownex.com/flownex-demoons or provide you with a demonstration of this fantastic tool. .  You can email us at info@padtinc.com or give us a call at 480.813.4884 or 1-800-293-PADT.

## Aerospace Summit, Additive Manufacturing Peer Group, and Industry-Education Partnership – A Three Event, Three State Hat Trick

Sometimes everything happens at once.  This June 22nd was one of those days.  Three key events were scheduled for the same time in three different states and we needed to be at all of them. So everyone stepped up and pulled it off, and hopefully some of you reading this were at one of these fantastic events.  Combined they are a great example of PADT’s commitment to the local technology ecosystem, showing how we create true win-win partnerships across organizations and geographies.   Since the beginning we wanted to be more than just a re-seller or just consultants, and this Thursday was a chance to show our commitment to doing just that.

## Albuquerque: New Mexico Technology Council 3D Printing Peer Group Kickoff

Everyone talks about how they thing we should all work together, but there never seems to be someone who is willing to pull it all together. That is how the additive manufacturing committee in New Mexico was until the New Mexico Technology Council (NMTC) stepped up to host a peer group around 3D Printing.  Even though it was a record 103f in Albuquerque, 35 brave 3D Printing enthusiasts ventured out into the heat and joined us at Rio Bravo Brewing to get the ball rolling on creating a cooperative community.  We started with an introduction from NMTC, followed by an overview of what we want to achieve with the group. Our goals are:

1. Create stronger cooperation between companies, schools, and individuals involved in 3D Printing in New Mexico
2. Foster cooperation between organizations to increase the benefits of 3D Printing to New Mexico
3. Make a contribution to New Mexico STEM education in the area of 3D Printing

To make this happen we will meet once a quarter, be guided by a steering committee, and grow our broad membership.  Anyone with any involvement in Additive Manufacturing in the state is welcome to join in person or just be part of the on-line discussion.

Then came the best part, where we went around the room and shared our names, orginization, and what we did in the world of 3D Printing.  What a fantastic group.  From a K-12 educator to key researchers at the labs, we had every industry and interest representing. What a great start.

Here are the slides from that part of the presentation:

Once that was done PADT’s Rey Chu gave a presentation where it went over the most important developments in Additive Manufacturing over the last year or so.  He talked about the three new technologies that are making an impact, new materials, and what is happening business wise.  Check out his slides to learn more:

After a question and answer period we had some great conversations in small groups, which was the most valuable part.

If you want to learn more, please reach out to info@padtinc.com and we will add you to the email list where we will plan and execute future activities.  We are also looking for people to be on the steering committee and locations for our next couple of meetings. Share this with as many people as you can in New Mexico so that next event can be even better!

## Denver: MSU Advance Manufacturing & Engineering Sciences Building Opening

Meanwhile, in Denver it was raining.  In spite of that,  supporters of educating the next generation of manufacturers and engineers gathered for the opening of the Advanced Manufacturing and Engineering Sciences Building at Metropolitan State University.  This 142,000 sqft multi-disciplinary facility is located in the heart of downtown Denver and will house classes, labs, and local companies.  PADT was there to not only celebrate the whole facility, but we were especially excited about the new 3D Printing lab that is being funded by a \$1 million gift from Lockheed Martin.  A nice new Stratasys Fortus 900 is the centerpiece of the facility.  It will be a while before the lab itself is done, so watch for an invite to the grand opening.  While we wait we are working with MSU, Lockheed Martin, Stratasys, and others to put a plan together to develop the curriculum for future classes and making sure that the engineers needed for this technology are available for the expected explosion of use of this technology.

Phoenix:  2017 Aerospace, Aviation, Defense + Manufacturing Conference

The 113f high in Phoenix really didn’t stop anyone from coming to the AADM conference. This annual event was at ASU SkySong in Phoenix and is sponsored by the AZ Tech Council, AZ Commerce Authority, and RevAZ.  PADT was proud to not only be a sponsor, but also have a booth, participate in the advanced manufacturing panel discussion, and do a short partner presentation about what we do for our Aerospace and Defense Customers.

Here is Rob’s presentation on PADT:

We had great conversations at our booth with existing customers, partners, and a few people that were new to us.  This is always one of the best events of the summer, and we look forward to next year.

Researchers and students at universities around the world are tackling difficult engineering and science problems, and they are turning to simulation more and more to get to understanding and solutions faster. Just like industry. And just like industry they are finding that ANSYS provides the most comprehensive and powerful solution for simulation. The ANSYS suite of tools deliver breadth and depth along with ease of use for every level of expertise, from Freshman to world-leading research professors. The problem in the past was that academia operates differently from industry, so getting to the right tools was a bit difficult from a lot of perspectives.

Now, with the ANSYS Academic program, barriers of price, licensing, and access are gone and ANSYS tools can provide the same benefits to college campuses that they do to businesses around the world.  And these are not stripped down tools, all of the functionality is there.

### Students – Free

Yes, free.  Students can download ANSYS AIM Student or ANSYS Student under a twelve month license.  The only limitation is on problem size.  To make it easy, you can go here and download the package you need.  ANSYS AIM is a new user interface for structural, thermal, electromagnetic, and fluid flow simulation oriented towards the new or occasional user.  ANSYS Student is a size limited bundle of the full ANSYS Mechanical, ANSYS CFD, ANSYS Autodyn, ANSYS SpaceClaim, and ANSYS DesignXplorer packages.

That is pretty much it. If you need ANSYS for a class or just to learn how to use the most common simulation package in industry, download it for free.

### Academic Institutions – Discounted Packages

If you need access to full problem sizes or you want to use ANSYS products for your research, there are several Academic Packages that offer multiple seats of full products at discounted prices. These products are grouped by application:

• Structural-Fluid Dynamics Academic Products — Bundles that offer structural mechanics, explicit dynamics, fluid dynamics and thermal simulation capabilities. These bundles also include ANSYS Workbench, relevant CAD import tools, solid modeling and meshing, and High Performance Computing (HPC) capability.
• Electronics Academic Products — Bundles that offer high-frequency, signal integrity, RF, microwave, millimeter-wave device and other electronic engineering simulation capabilities. These bundles include product such as ANSYS HFSS, ANSYS Q3D Extractor,ANSYS SIwave, ANSYS Maxwell, ANSYS Simplorer Advanced. The bundles also include HPC and import/connectivity to many common MCAD and ECAD tools.
• Embedded Software Academic Products — Bundles of our SCADE products that offer a model-based development environment for embedded software.
• Multiphysics Campus Solutions— Large task count bundles of Research & Teaching products from all three of the above categories intended for larger-scale deployment across a campus, or multiple campuses.

There are many options on price and bundling based upon need and other variables, so you will need to contact PADT or ANSYS to help sort it all out and find the right fit for your organization.

What does all this mean?  It means that every engineer graduating from their school of choice should enter the workforce knowing how to use ANSYS Products, something that employers value. It also means that researchers can now produce more valuable information in less time for less money because they leverage the power of ANSYS simulation.The barriers are down, as students and institutions, you just need to take advantage of it.

## Robust Meshing for FEA with ANSYS

Meshing is one of the most important aspects of a simulation process and yet it can be one of the most frustrating and difficult to get right.  Whether you are using CAD based simulation tools or more powerful flagship simulation tools, there are different approaches to take when it comes to meshing complicated assemblies for structural or thermal analysis.

ANSYS has grown into the biggest simulation company globally by acquiring powerful technologies, but more importantly, integrating their capabilities into a single platform.  This is true for meshing as well.  Many of ANSYS’ acquisitions have come with several strong meshing capabilities and functionalities and ANSYS Workbench integrates all of that into what we call Workbench Meshing.  It is a single meshing tool that incorporates a variety of global and local mesh operations to ensure that the user not only gets a mesh, but gets a good quality mesh without needing to spend a lot of time in the prep process. We’ll take a look at a couple examples here.

TRACTOR AXLE

This is a Tractor Axle assembly that has 58 parts including bolts, gaskets and flanges.  The primary pieces of the assembly also has several holes and other curved surfaces.  Taking this model into Workbench Meshing yielded a good mesh even with default settings. From here by simply adding a few sizing controls and mesh methods we quickly get a mesh that is excellent for structural analysis.

Tractor Axle Geometry

Tractor Axle Default Mesh

Tractor Axle Refined Mesh

RIVETING MACHINE

The assembly below, which is a model from Grabcad of a riveting machine, was taken directly into Workbench Meshing and a mesh was created with no user input. As you can see the model has 5,282 parts of varying sizes, shapes and complexity.  Again without needing to make any adjustments, Workbench Meshing is able to mesh this entire geometry with 6.6 million elements in only a few minutes on a laptop.

Riveting Machine

Riveting Machine

Riveting Machine Default Mesh

Riveting Machine Default Mesh

The summary of the meshing cases are shown below:

 Case # of Parts User Operations # of Elements # of Nodes Time [s] Tractor Axle 58 0 415,735 723,849 34 Tractor Axle Refined 58 5 Body Sizings 2 Local Mesh Methods 930,406 1,609,703 43 Riveting Machine 5,282 0 2,481,275 6,670,385 790

Characteristics of a robust meshing utility are:

• Easy to use with enough power under the hood
• Able to handle complex geometry and/or large number of parts
• Quick and easy user specified mesh operations
• Fast meshing time

ANSYS Meshing checks all of these boxes completely.  It has a lot of power under the hood to handle large and/or complex geometry but makes it simple and easy for users to create a strong quality mesh for FEA analysis.

If you would like a more detailed step-by-step explanation of this process, check out the video below!

If you have any questions feel free to reach out to me at manoj@padtinc.com

Credit to Manoj Abraham from Grabcad for Riveting Machine Model. And no I didn’t choose this model just because he shared my name

## Combining ANSYS Simulation with HPC

Engineering simulation has become much more prevalent in engineering organizations than it was even 5 years ago.  Commercial tools have gotten significantly easier to use whether you are looking at tools embedded within CAD programs or the standalone flagship analysis tools.  The driving force behind these changes are to ultimately let engineers and companies understand their design quicker with more fidelity than before.

Engineering simulation is one of those cliché items where everyone says “We want more!”  Engineers want to analyze bigger problems, more complex problems and even do large scale design of experiments with hundreds of design variations – and they want these results instantaneously.   They want to be able to quickly understand their designs and design trends and be able to make changes accordingly so then can get their products optimized and to the market quicker.

ANSYS, Inc. spends a significant amount of R&D in helping customers get their results quicker and a large component of that development is High Performance Computing, or HPC.  This technology allows engineers to solve their structural, fluid and/or electromagnetic analyses across multiple processors and even across multiple computing machines.  Engineers can leverage HPC on laptops, workstations, clusters and even full data centers.

PADT is fortunate to be working with Nimbix, a High Performance Computing Platform that easily allowed us to quickly iterate through different models with various cores specified.  It was seamless, easy to use, and FAST!

Let’s take a look at four problems: Rubber Seal FEA, Large Tractor Axle Model, Quadrocopter CFD model and a Large Exhaust CFD model.  These problems cover a nice spectrum of analysis size and complexity. The CAD files are included in the link below.

TRACTOR AXLE FEA

This model has several parts all with contact defined and has 51 bolts that have pretension defined.  A very large but not overly complex FEA problem.  As you can see from the results, even by utilizing 8 cores you can triple your analysis throughput for a work day.  This leads to more designs being analyzed and validated which gives engineers the results they need quicker.

SUMMARY

• 58 Parts
• 51 x Bolts with Pretension
• 928K Elements, 1.6M Nodes
 Cores Elapsed Time [s] Estimated Models Per 8 [hours] 2 14,525 2 4 9,710 3 8 5,233 6 16 4,009 7

RUBBER SEAL FEA

The rubber seal is actually a relatively small size problem, but quite complex.  Not only does it need full hyperelastic material properties defined with large strain effects included, it also includes a leakage test.  This will pressurize any exposed areas of the seal.  This will of course cause some deformation which will lead to more leaked surfaces and so on.  It basically because a pressure advancing solution.

From the results, again you can see the number of models that can be analyzed in the same time frame is signifcantly more.  This model was already under an hour, even with the large nonlinearity, and with HPC it was down to less than half an hour.

SUMMARY

• 6 Parts
• Mooney Rivlin Hyperelastic Material
• Frictional Contact
• Large Deformation
• 42K Elements, 58K Nodes
 Cores Elapsed Time [s] Estimated Models Per 8 [hours] 2 3,353 9 4 2,489 12 8 1,795 16

The drone model is a half symmetry model that includes 2 rotating domains to account for the propellers.  This was ran as a steady state simulation using ANSYS Fluent.  Simply utilizing 8 cores will let you solve 3 designs versus 1.

SUMMARY

• Multiple Rotating Domains
• 2M Elements, 1.4M Nodes
 Cores Elapsed Time [hours] Speedup 2 2.1 1 4 1.2 1.8 6 0.8 2.6 8 0.7 3

EXHAUST CFD

The exhaust model is a huge model with 33 million elements with several complicated flow passages and turbulence.  This is a model that would take over a week to run using 1 core but with HPC on a decent workstation you can get that down to 1 day.  Leveraging more HPC hardware resources such as a cluster or using a cloud computing platform like Nimbix will see that drop to 3 hours.  Imagine getting results that used to take over 1 week that now will only take a few hours.  You’ll notice that this model scaled linearly up to 128 cores.  In many CFD simulations the more hardware resources and HPC technology you throw at it, the faster it will run.

SUMMARY

• K-omega SST Turbulence
• Multi-Domain
• 33M Elements, 7M Nodes
 Cores Elapsed Time [hours] Speedup 16 26.8 1 32 13.0 2.1 64 6.8 3.9 96 4.3 6.2 128 3.3 8.2

As seen from the results leveraging HPC technology can be hugely advantageous.  Many simulation tools out there do not fully leverage solving on multiple computing machines or even multiple cores.  ANSYS does and the value is easily a given.  HPC makes large complex simulation more practical as a part of the design process timeline.  It allows for greater throughput of design investigations leading to better fidelity and more information to the engineer to develop an optimized part quicker.

If you’re interested in learning more about how ANSYS leverages HPC or if you’d like to know more about NIMIBX, the cloud computing platform that PADT leverages, please reach out to me at manoj@padtinc.com

## When the going gets tough, the tough use ANSYS for CFD Meshing

If you do CFD simulations then you know the struggle that is involved in meshing. It is a fine balance of accuracy, speed, and ease of set up. If you have complex geometry, large assemblies, or any difficulty meshing then this blog article is for you.

## Why should I spend time making a good mesh?

The mesh is arguably one of the most important parts of any simulation set up. A good mesh can solve significantly faster and provide more accurate results. Conversely, a poor mesh can make the simulation have inaccurate results and be slow to converge or not converge at all. If you have done any simulation then you know that hitting the solve button can feel like rolling the dice if you don’t have a robust meshing tool.

## When is it going to matter?

A good mesh is going to matter on a Friday afternoon when you need to get the simulation started before you leave for the weekend because it takes two days to run and you need to deliver results on Monday but you are up against the clock because you have to get to your kid’s soccer game by 5pm and the mesh keeps crashing.

A poor mesh can do more than just reorganizing you’re social agenda. A poor mesh can drastically change results like pressure drop in an internal flow passage or drag over a body. If you go into that meeting on Monday and tell your boss that the new design is going to perform 10% better than the previous design – you need to be confident that the design is 10% better not 10% worse.

## What should I do when I need to create a good mesh?

If you’re the poor soul reading this on a Friday afternoon because you are trying to frantically fix you’re mesh so you can get your simulation running before the weekend – I pity you. Continue reading for my proprietary step by step approach titled “How to get you’re CFD mesh back on track!” (Patent pending).

### Step 1) Know your tools

ANSYS has been developing its meshing technology since the beginning of time (not really but almost) – it’s no surprise that its meshing algorithms are the best in the business. In ANSYS you have a large number of tools at your disposal, know how to use them.

The first tool in your toolbox is the ANSYS automatic meshing technology. It is able to predictively apply settings for your part to get the most accurate automatic mesh possible. It has gotten so good that the automatic mesh is a great place to start for any preliminary simulations. If you want to get into the details, ANSYS meshing has two main groups of mesh settings – Global Meshing Parameters and Local Meshing Parameters. Global mesh parameters are great for getting a good mesh on the entire model without going into detailed mesh settings for each part.

But when you do have to add detailed meshing settings on a part by part basis then local mesh settings won’t let you down.

### Step 2) Know your physics

What is your primary result of interest? Drag? Pressure drop? Max velocity? Stagnation? If you can quantify what you are most interested in then you can work to refine the mesh in that region so as to capture the physics accurately. ANSYS allows you set local sizing parameters on bodies, faces, lines, and regions which allow you to get the most accurate mesh possible but without having to use a fine mesh on the entire part.

### Step 3) Know your mesh quality statistics

Mesh quality statistics can be a good way to gauge the health of your mesh. They are not a foolproof method for creating a mesh that will be accurate but you will be able to get an idea of how well it will converge. In ANSYS meshing there is a number of mesh quality statistics at your fingertips. A quick and easy way to check your mesh is to look at the Minimum Orthogonal Quality statistic and make sure it is greater than 0.1 and Maximum Skewness is less than 0.95.

### Step 4) Know your uncertainty

Every test, simulation, design, process etc… has uncertainty. The goal of engineering is to reduce that uncertainty. In simulation meshing is always a source of uncertainty but it can be minimized by creating high quality meshes that accurately model the actual physical process. To reduce the uncertainty in meshing we can perform what is called a mesh refinement study. Using the concept of limits we can say that in the limit of the mesh elements getting infinitely small than the results will asymptotically approach the exact solution. In the graph below it can be seen that as the number of elements in the model are increased from 500 – 1.5million the result of interest approached the dotted line which we can assume is close to the exact solution.

By completing a mesh refinement study as shown above you can be confident that the mesh you have created is accurately capturing the physics you are modeling because you can quantify the uncertainty.

If you currently just skip over the meshing part of your CFD analysis thinking that it’s good enough or if your current meshing tool doesn’t give you any more details than just a green check mark or a red X then it’s time dig into the details of meshing and start creating high quality meshes that you can count on.

For more info about advanced meshing techniques in ANSYS – see this PDF presentation that is a compilation of ANSYS training material on the meshing subject.

If you still haven’t figured out how to get your mesh to solve and its 5pm on Friday see below*

*Common pitfalls and mistakes for CFD meshing:

• Choose your turbulence model wisely and make sure your mesh meets the quality metrics for that model.
• Make sure you don’t have boundary conditions near an area of flow recirculation. If you are getting reverse flows at the boundary then you need to move your boundary conditions further away from the feature that’s causing the flow to swirl in and out of the boundary.

## How-To: Creating Matching Faces on Touching Parts with ANSYS SpaceClaim

Sometimes you want to take two parts and and prepare them for meshing so that they either share a surface between them, or have identical but distinct surfaces on each part where they touch.  In this simple How-To, we share the steps for creating both of these situations so you can get a continuous mesh or create a matching contact surface in ANSYS Mechanical.