Using Bright CM to Manage a Linux Cluster

COD_Cluster-Bright-1What goes into managing a Linux HPC (High Performance Computing) cluster?

There is an endless list of software, tools and configurations that are required or recommended for efficiently managing a shared HPC cluster environment.

A shared HPC cluster typically has many layers that deliver a usable environment that doesn’t have to  depend on the users coordinating closely or the system administrators being superheroes of late-night patching and just-in-time recovery.

bright-f1

Figure 1 Typical Layers of a shared HPC cluster.

For each layer in the diagram above there are numerous open-source and paid software tools to choose from. The thing to note is that it’s not just a choice. System administrators have to work with the user requirements, compatibility tweaks and ease of implementation and use to come up with a perfect recipe (much like carrot cake). Once the choices have been made, users and system administrators have to train, learn and start utilizing these tools.

HPC @ PADT Inc.

At PADT Inc. we have several Linux based HPC clusters that are in high demand. Our Clusters are based on the Cube High Value Performance Computing (HVPC) systems and are designed to optimize the performance of numerical simulation software. We were facing several challenges that are common with building & maintaining HPC clusters. The challenges were mainly in the areas of security, imaging and deployment, resource management, monitoring and maintenance.

To solve these challenges there is an endless list of software tools and packages both open-source and commercial. Each one of these tools comes with its own steep learning curve and mounting time to test & implement.

Enter – Bright Computing

After testing several tools we came across the Bright Computing – Bright Cluster Manager (Bright CM). Bright CM eliminates the need for system administrators to manually install and configure the most common HPC cluster components. On top of that it provides the majority of the HPC software packages, tools and software libraries in their default software image.

A Bright CM cluster installation starts off with an extremely useful installation wizard that asks all of the right questions while giving the user full control to customize the installation. With a note pad, a couple of hours and a basic understanding of HPC clusters, you are ready to install your applications.

bright-f2

Figure 2. Installation Wizard

An all knowing dashboard helps system admins master and monitor the cluster(s) or if you prefer the CLI CM shell provides full functionality through command line. From the dashboard system admins can manage multiple clusters down to the finest details.

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Figure 3. Cluster Management Interface.

An extensive cluster monitoring interface allows systems admins, users and key stakeholders to generate and view detailed reports about the different cluster components.

bright-f4

Figure 4. Cluster Monitoring Interface.

Bright CM has proven to be a valuable tool in managing and optimizing our HPC environment. For further information and a demo of Bright Cluster Manager please contact sales@padtinc.com.

10 Useful New Features in ANSYS Mechanical 16.0

ansys-mechanical-16-heade2r

PADT is excited about the plethora of new features in release 16.0 of ANSYS products.  After sorting through the list of new features in Mechanical, here are 10 enhancements that we found to be particularly useful for general applications.


1: Mesh Display Style

This new option in the details view for the mesh branch makes it easy to visualize mesh quality items such as aspect ratio, skewness, element quality, etc.  The default style is body color, but it can be changed in the details to element quality, for example, as shown here:

ansys-mechanical-16-f1a

Figure 1. A. – Mesh Display Style Set to Element Quality

figure1b

Figure 1. B. – Element Quality Plot After Additional Mesh Settings

ansys-mechanical-16-f1c

Figure 1. C. – Accessing Display Style in the Mesh Details


2: Image to Clipboard

How many times have you either done a print screen > paste into editing tool > crop or done an image to file to get the plots you need into tools such as Word and PowerPoint?  The new Image to Clipboard menu pick streamlines this process.  Now, just get the image the way you want it in the geometry view, right click, and select Image to Clipboard.  Or just use Ctrl + C.  When you paste, you’ll be pasting the contents of that view window directly.  Here’s what it looks like:

ansys-mechanical-16-f2

Figure 2 – Right Click, Image to Clip Board


3: Beam Contact Formulation

This was a beta feature at 15.0, but if you didn’t get a chance to try it out, it’s now fully supported at 16.0.  The idea here is that instead of the ‘traditional’ bonded contact methods (using the augmented Lagrange or pure penalty formulation) or the Multi-Point Constraint (MPC) bonded option, we now have a new choice of beam contact.  This option utilizes internally-created massless linear beam elements to connect the two sides of a contact interface together.  This can be more efficient than the traditional formulations and can avoid the over constraints that can happen if multiple contact regions utilizing the MPC option end up generating constraint equations that tend to conflict with each other.

ansys-mechanical-16-f3

Figure 3 – Beam Formulation for Bonded Contact


4: Nonlinear Adaptive Region

If you have ever been frustrated by the error message in the Solution Information window that says, “Element xyz … has become highly distorted…”, version 16.0 adds a new tool to our toolbox with the Nonlinear Adaptive Region capability.  This capability is in its infancy stage at 16.0, but in the right circumstances it allows the solution to recover from highly distorted elements by pausing, remeshing, and then continuing.  We plan on publishing more details on this capability soon, but for now please know that it exists and more can learned in the 16.0 Mechanical Help.  There are a lot of restrictions on when it can work, but a big one is that it only works for elements that become overly deformed due to large and nonuniform deformation, meaning not due to unstable materials, numerical instabilities, or structures that are unstable due to buckling effects.

As shown in figure 4. A., a Nonlinear Adaptive Region can be inserted under the Solution branch.  It is scoped to bodies.  Options and controls are set in the details view.

ansys-mechanical-16-f4a

Figure 4. A. – Nonlinear Adaptive Region

If the solver encounters a ‘qualifying event’ that triggers a remesh, the solver output will inform us like this:

 

**** REGENERATE MESH AT SUBSTEP     5 OF LOAD STEP      1 BECAUSE OF
      NONLINEAR ADAPTIVE CRITERIA

 

 

 

 

AmsMesher(ANSYS Mechanical Solver Mesher),Graph based ANSYS Meshing EXtension,v0.96.03b
(c)ANSYS,Inc. v160-20141009
  Platform           :  Windows 7 6.1.7601
  Arguments          :  F:\Program Files\ANSYS Inc\v160\ANSYS\bin\winx64\AnsMechSolverMesh.exe
                     :  -m
                     :  G:\Testing\16.0\_ProjectScratch\Scr692\file_inpRzn_0001.cdb
                     :  –slayers=2
                     :  –silent=0
                     :  –aconcave=15.0000
                     :  –aconvex=15.0000
                     :  –gszratio=1.0000
  Seed elements      :  _RZNDISTEL block

– 17:6:17 2015-2-11

  ===================================================================
  == Mesh quality metrics comparison                                
  ===================================================================
  Element Average    :  ——–Source——–+——–Target——–
  ..Skewness(Volume) :    4.0450e-001             4.1063e-001        
  ..Aspect Ratio     :    2.3411e+000             2.4331e+000        
  Domain Volume      :    8.6109e-003             8.6345e-003        

  Worst Element      :  ——–Source——–+——–Target——–
  ..Skewness(Volume) :    0.8564  (e552     )      0.7487  (e2217    )   
  ..Aspect Ratio     :    4.9731  (e434     )      6.8070  (e2236    )   

  ===================================================================
  == Remeshing result statistics                                    
  ===================================================================
  Domain(s)          :   1      
  Region(s)          :   1      
  Patche(s)          :   7      
  nNode[New]         :   39      
  nElem[New/Eff/Src] :   79 / 92 / 2076      

  Peak memory        :   10 MB

– 17:6:17 2015-2-11
– AmsMesher run completed in 0.225 seconds

  ========================= End Run =================================
  ===================================================================

 **** NEW MESH HAS BEEN CREATED SUCCESSFULLY. CONTINUE TO SOLVE. 

Results item tabular listings will show that a remesh has occurred, as shown in figure 4. B.

ansys-mechanical-16-f4b

Figure 4. B. – Results Table Indicating a Remesh Occurred in the Nonlinear Adaptive Region

ansys-mechanical-16-f4c

Figure 4. C. – Before and After Remesh Due to Nonlinear Adaptive Region


5: Thermal Fluid Flow via Thermal ‘Pipes’

This has also been a beta option in prior releases, but nicely, at 16.0 it becomes a production feature.  The idea here is that we can use the ANSYS Mechanical APDL FLUID116 elements in Mechanical, without needing a command object.  These fluid elements have temperature as their degree of freedom in this case, and enable the effects of one dimensional fluid flow.  This means we have a reduced order model for capturing heat transfer due to a fluid moving through some kind of cavity without having to explicitly model that cavity.  The pipe ‘path’ is specified using a line body.

The line body gets defined with a cross section in CAD, and is tagged as a named selection in Mechanical.  This thermal pipe can then interact on appropriate surfaces in your model via a convection load.  Once the convection load is applied on appropriate surfaces in your model, the Fluid Flow option can then be set to Yes, and the line body is specified as the appropriate named selection.  Appropriate BC’s need to be applied to the line body, such as temperature constraints and mass flow rate, as shown in figure 5.

ansys-mechanical-16-f5

Figure 5 – Thermal “Pipe” Line Body at Top, Showing Applied Boundary Conditions


6: Solver Pivot Checking Control

This new option under Analysis Settings > Solver Controls allows you to potentially continue an analysis that has stopped due to pivoting issues, meaning a model that’s not fully constrained or one that is having trouble due to contact pairs not being fully in contact. 

The options are Program Controlled, Warning, Error, and Off.  The Warning setting is the one to use if you want the solver to continue after any pivoting issues have occurred.  The Error setting means that the solver will stop if pivoting issues occur.  The Off setting results in no pivot checking to occur, while Program Controlled, which is the default, means that the solver will decide.

ansys-mechanical-16-f6

Figure 6 – Solver Pivot Checking Controls Under Analysis Settings


7: Contact Result Trackers

This new feature allows you to more closely track contact status data while the solution is running, or after it has completed.  This capability uses the .cnd file that is created during the solution in the solver directory.  It is useful because it gives you more information on the behavior of your contact regions during solution so you can have more confidence that things are progressing well or potentially stop the solution and take corrective action if they are not.  The tracker objects get inserted under the Solution Information branch, as shown in figure 7. A.

ansys-mechanical-16-f7a

Figure 7. A. – Contact Trackers Inserted Under Solution Information

A large variety of quantities can be selected to track, such as Number Contacting, Number Sticking, Gap, Penetration, etc.

ansys-mechanical-16-f7b

Figure 7. B. – Contact Results Tracker Settings in the Details View

Contact results tracker quantities can be viewed in real time during the solution, as shown in figure 7. C.

ansys-mechanical-16-f7c

Figure 7. C. – Contact Results Tracker Showing Gap Decreasing as the Solution Progresses


8: Tree Filtering

For large assemblies or other complex models, there are useful enhancements in how the tree can be filtered, including the ability to create Groups.  Groups can consist of tree entities that are geometry, coordinate systems, connection features, boundary conditions, or even results.  Grouping is accomplished as easily as selecting the desired items in the tree, then right clicking to specify Group, as shown in Figure 8. A.

ansys-mechanical-16-f8a

Figure 8. A. – Grouping Displacements

A new folder in the tree is then created which can be named something useful.  Figure 8. B. shows the displacement boundary condition group (folder) after it was given a name.

ansys-mechanical-16-f8b

Figure 8. B. – Group of Displacement BC’s, Given a Meaningful Name

It’s easy to right click and Ungroup if needed, and there is also a Group Similar Objects option which allows you to select just one item in the tree and easily group all similar items by right clicking.


9: Results Set Listing Enhancements

In addition to the information on remeshing that we mentioned back in useful new feature number 4, there is a new capability to right click in the tabular listing of results and then right click to create total deformation or equivalent stress results.  This capability can make it faster to create a deformation or stress plot for a particular time point or result set of interest.

The procedure to do this is:

  • Left click on the Solution branch in the tree.
  • Left click on the desired Results set in Tabular Data
  • Right click on that results set and select Create Total Deformation Results or Create Equivalent Stress Results, as shown in figure 9.

The result of these steps will be a new result item in the tree, waiting for you to evaluate so you can see the new results plot.

ansys-mechanical-16-f9

Figure 9 – Right Click in Solution Tabular Data to Create Deformation or Equivalent Stress Result Items


10: Explode View

We’ve saved a fun one for last, the new Explode View capability.  This allows you to incrementally ‘explode’ the view of your assemblies, making it potentially easier to visualize the parts and interaction between parts that make up the assembly.  To use this feature, make sure the Explode View Options toolbar is turned on in your View settings.  There are several options for the ‘explosion center’, such as the assembly center or the global or a user defined coordinate system.

ansys-mechanical-16-f10a 

Figure 10. A. – The Explode View Options Toolbar

As you can see in figure 10. A., there is a slider that allows you to control the ‘level’ of view explosion.  Keep in mind this is just a visual tool and does nothing to the coordinates of the parts in your assemblies.

Figures 10. B. and 10. C. show various slider settings for the exploded view of an assembly.

ansys-mechanical-16-f10b

Figure 10. B. – Explode View Level 3

ansys-mechanical-16-f10c

Figure 10. C. – Explode View Level 4


This concludes our tour of 10 useful new features in ANSYS Mechanical 16.0.  We hope you find this information helps you get your ANSYS Mechanical simulations completed more efficiently.  There are lots and lots of other new features that we didn’t mention here.  The Release Notes in the Help covers a lot of them.  We’ll be writing more about some of the things we mentioned here as well as some of the other new features soon.  

PADT’s ANSYS Sales Team Celebrates Sales Record for 2014

2014 was both a challenging and rewarding year at PADT. One area of the company that achieved success last year was the ANSYS Sales team.  Lead by Bob Calvin, our account  managers Oren Raz and Patrick Barnett worked with the support of our technical team  throughout the year to help our customers find the right solution for their simulation needs. All that hard work resulted in a record year of sales for ANSYS products by PADT.

A big "Thank You" needs to go out to all of our fantastic customers who make selling and supporting this tool such a pleasure. Our success is a direct result of the success that they are having in the application of ANSYS, Inc. technology to improve their products and their product development process. I know that sounds kind of "salesy" but it is true.  We keep selling more of this stuff for one simple reason, it works. 

And making it work is also the job of our technical support team, our engineers who serve as application engineers, and the business support staff that takes care of the details. 

 This week we were lucky to have Bob Thibeault, the new ANSYS Director North America Channel, and Clark Cox, the ANSYS Channel Account Manager, visit Phoenix and we were able to get a picture with them as we placed our 6th annual sales achievement medal on our "wall o' awards."

PADT-2014-ANSYS-Sales-Achievement-Award
2014 Accomplished – Putting the medal on the wall
(L to R) Clark Cox, Bob Thibeault, Ward Rand, Eric Miller, Bob Calvin

Things are already off to a great start for 2015 and we hope to be working with even more customers as we help them explore new and profitable ways to apply this technology. 

Quick Tip: Concatenating Text Files Using ANSYS Mechanical APDL

So you have text output from some ANSYS analysis and you wish you could just do this:

cat lift.txt  cop.txt drag.txt >> results.txt

and you are writing an ANSYS macro and want it to run on all platforms.  The following macro will use APDL commands to join the files together. 

macro1.mac

/inquire,linesin1,lines,lift,txt

*sread,str1array,lift,txt,,80,,linesin1

/inquire,linesin2,lines,cop,txt

*sread,str2array,cop,txt,,80,,linesin2

/inquire,linesin3,lines,drag,txt

*sread,str3array,drag,txt,,80,,linesin3

*cfopen,results,txt

*vlen,linesin1

*vwrite,str1array(1)

%80S

*vlen,linesin2

*vwrite,str2array(1)

%80S

*vlen,linesin3

*vwrite,str3array(1)

%80S

*cfclose

Bonus: If you want to strip some lines off of the top or read less than all the lines, you can pass additional arguments to *sread:

/inquire,linesin1,lines,lift,txt

Lines_skip=5

Lines_read=linesin1-lines_skip

*sread,str1array,lift,txt,,80,lines_skip,lines_read

 

Seminar Info: Designing and Simulating Products for 3D Printing

Note: We have scheduled an encore Lunch & Learn and companion Webinar for March 23, 2015.  Please register here to attend in person at CEI in Phoenix or here to attend via the web.

ds43dp-1People are interested in how to better do design and simulation for products they manufacture using 3D Printing.  When the AZ Tech council let us know they had a cancelation for their monthly manufacturing Lunch and Learn, we figured why not do something on this topic, a few people might show up. We had over 105 people register, so we had to close registration. In the end around 95 total people made it to the seminar, which is more than expected so we had to add chairs. Who would have thought that many people would come for such a nerdy topic?.

For an hour and fifteen minutes they sat and listned to us talk about the ins and outs of using this growing technology to make end use parts.  Here is a copy of the PowerPoint as a PDF.

We did add one bullet item in the design suggestions area based on a question. Someone pointed out that the machine instructions, what the AM machine uses to make the parts, should be a controlled document. They are exactly right and that is a very important process that needs to be put in place to get traceability and repeatability.  

Here are some useful links:

As always, do not hesitate to contact us for more information or with any questions.

If you missed this presentation, don't worry, we are looking to schedule a live/web version of this talk with some enhancements sometime in March.  Watch the usual channels for time, place, and registration information. We will also be publishing detailed blog posts on many of the topics covered today, diving deeper into areas of interest.

Thank you to the AZ Tech Council, ASU SkySong, and everyone that attended for making this our best attended non-web seminar ever.

Design and Simulation for 3D Printing Full House

The Full Power of SpaceClaim Engineer – Now Available from PADT

SpaceClaim-1We have been using SpaceClaim with ANSYS Workbench for about four years now, and we always liked it. Then it came as part of the Geomagic Spark tool and we got more excited.  This was a powerful geometry creation, editing, and reapir tool that was saving us time all across PADT.  The, when ANSYS, Inc. purchased the company SpaceClaim we got realy excited.  So excited that we decided to become a reseller of the full product, and not just the ANSYS or Geomagic tools.  The addition of a module for working with STL files sealed the deal and as of the begining of the year we are offering all flavors of SpaceClaim to our customers.

The official press release can be found here. You can learn a lot about the product by visiting the web page.

To get started learning about why we love this program so much, check out this video showing the new features in the latest version:

Then go visit their YouTube channel and watch videos that may be of special interest to you.

Or, contact us here at PADT and we would be happy to share with your our enthusiasm for this tool.

SpaceClaim-Model1b

 

Deflategate Update: ANSYS Simulation Shows it Really Does not Make a Difference.

There is still more debate going on about the deflated footballs that the New England Patriots used in their playoff game. "Who Deflated Them? When? Were they acting on orders?"  But no one is asking if it makes a real difference.

Enter ANSYS simulation software. Using the newest ANSYS product, ANSYS AIM, the engineers at ANSYS, Inc. were able to simulate the effect of lower pressure on grip. It turns out that the the difference in pressure only made a 5mm difference in grip. No big deal.  

Being a Multiphysics tool they were able to quickly also run a flow analysis and see what impact drag from "wobble" had on a pass.  A 10% off axis wobble resulted in 20% more drag, that is a few yards on a long pass.  Their conclusion, throwing a tight spiral is more important than the pressure of the ball.

Check out the full article on the ANSYS blog: 

http://www.ansys-blog.com/superbowl-deflategate-scandal-debunked-using-engineering-simulation/#more-11576

Here is the video as well:

Donny Don’t – Remote Objects

Nothing like a good ‘ol fashion Simpson’s reference.  I’m trying to start a new series of articles that address common mistakes and things to avoid, and what better reference than when Bart ‘joined’ the Junior Campers and found out he might get a knife out of the deal. 

6lrWlDO

For this first article, let’s talk about remote objects (force, displacement, points, joints).  First, remote objects are awesome.  Want to add a rotational DOF to your solid-object model?  Remote Displacement.  Want to apply a load and don’t want to worry about force/moment balance?  Remote Force.  Want to apply a load but also constrain a surface?  Remote Point.  Take two points and define a open/locked degrees of freedom and you have a kinematic joint.

The thing to watch out for is how you define these remote points.  ANSYS Mechanical does an amazing job at making a pretty tedious process easy (create pilot node, create constraint-type contact, specify DOFs to include, specify formulation).  In Mechanical, all you need to do is highlight some geometry, right mouse click, and insert the appropriate object (remote point, remote force, etc).  No need to keep track of real constant sets, element tshape’s…easy.  Almost too easy if you ask me.

Once you start creating multiple remote objects, you may see the following:

message1

If you dig into the solver output file you may see this:

image

The complaint is that we have multiple overlapping constraint sets.  Let’s take a step back and see the model I’ve setup:

image

I have a cylinder, attached to a body-to-ground spring on one face, a translational joint applied on the OD, and a remote force and moment applied on the opposite end.  If I follow the instructions shown from the ANSYS Workbench message about graphically displaying FE Connections (select the ‘Solution Information’ item, click the graphics tab):

image

We can see that any type of constraint equation is shown in red.  The issue here is that the nodes on the OD edge on the top and bottom of my cylinder belong to multiple constraint equation sets.  On the bottom my my cylinder those nodes are being constrained to the spring end AND the cylindrical joint.  On the top the nodes on the edge are being constrained to the joint AND remote force.  When you hit solve, ANSYS needs to figure out how to resolve the conflicting constraint sets (a node cannot be a slave term for two different constraint sets).  I don’t know exactly how the solver manages this, but I like to imagine it’s like two people fighting over who gets to keep a dog…and they place the dog in-between them and call for it, and whoever the dog goes to gets to keep it. 

Now for this example, the solver is capable of handling the over-constraint because overall…the model is properly constrained.  The spring can loose some of the edge nodes and still properly connect to the cylinder.  Same goes for the other remote objects (translation joint and remote force/moment).  If we had more objects defined and more overlaps, that’s a different story.  You can introduce a pretty lengthy lag, or outright solver failure, if there are a lot of overconstraint terms in the model. 

So now the question becomes, how do I fix this.  The easiest way is to not fix this and ignore the warning.  If our part behaves properly, we get the reaction forces we’d expect, then odds are the overconstraint terms that are automatically corrected are fine.  If we actually wanted to remove that warning, we would need to make sure we scope remote objects that do not touch other remote objects.  We can do this by going into DesignModeler or SpaceClaim and imprinting the surfaces. 

image

In DM, I just extruded the edges with the operation set to imprint face.  In SpaceClaim you would just need to use the ‘copy edge’ option on the pull command:

image

Now this will modify the topology and will ensure we have a separation of nodes for all of our remote objects:

image

When we solve…no warning message about MPC conflicts:

image

And when we look at the FE connectivity, there are no nodes shared by multiple remote objects:

image 

The last thing I’d like to point out is the application of a force and moment on a remote point:

image

Whenever you have two remote objects operating on the same surface (e.g. a moment and force, force and displacement, etc), you should really be using a remote point.  If I were to create two remote objects:

image

I now come right back to my original problem of conflicting constraints.  These two objects share the exact same nodal set but are creating two independent remote points.  If you want to do this, right-mouse-click on one of your remote objects and select ‘promote to remote point’:

image

Then modify the other remote objects to use that remote point.  No more conflict. 

Very last point…in R16 it will now tell you when you have ‘duplicate’ remote objects  (like the remote force + displacement shown above). 

image

Hope this helps! 

Thermal Submodeling in ANSYS Workbench Mechanical 15.0

thermal-submodeling-18
If you've been following The Focus for a long time, you may recall my prior article about submodeling using ANSYS Mechanical APDL, which was a 'sub' model of a submarine.  The article, from 2006, begins on page 2 at this link:

Also, Eric Miller here at PADT wrote a Focus blog entry on the new-at-14.5 submodeling capability in ANSYS Workbench Mechanical.

Since both of those articles were about structural submodeling, I decided it was time we published a blog entry on how to perform submodeling in ANSYS Mechanical for thermal simulations.

Submodeling is a technique whereby we can obtain more accurate results in a small, detailed portion of a large model without having to build an incredibly refined and detailed finite element model of our complete system.  In short, we map boundary conditions onto a 'chunk' of interest that is a subset of our full model so that we can solve that 'chunk' in more detail.  Typically we mesh the 'chunk' with a much finer mesh than was used in the original model, and sometimes we add more detail such as geometric features that didn't exist in the original model like fillets.

The ANSYS Workbench Project Schematic for a thermal solution involving submodeling looks like this:

thermal-submodeling-1

Figure 1 – Thermal Submodeling Project Schematic

Note that in the project schematic, the links are automatically established when we setup the submodel after completing the analysis on the coarse model as we shall see below.

First, here is the geometry of the coarse model.  It's a simple set of cooling fins.  In this idealized model, no fillets have been modeled between the fins and the block.

thermal-submodeling-2

Figure 2 – Coarse Model Geometry, Idealized without Fillets

The boundary conditions consisted of a heat flux due to a  thermal source on the base face and convection to ambient air on the cooling fin surfaces.  The heat flux was setup to vary over the course of 3 load steps as follows:

Load Step        Heat Flux (BTU/s*in^2)

            1                      0.2

            2                      0.5

            3                      0.005

Thus, the maximum heat going into the system occurs in load step 2, corresponding to 'time' 2.0 in this steady state analysis.

thermal-submodeling-3

Figure 3 – Coarse Model Boundary Conditions – Heat Flux and Convection

The coarse model is meshed with relatively large elements in this case.  The mesh refinement for a production model should be sufficient to adequately capture the fields of interest in the locations of interest.  After solving, the temperature results show a max temperature at the base where the heat flux is applied, transitioning to the minimum temperature on the cooling fins where convection is removing heat.

thermal-submodeling-4

Figure 4 – Coarse Model Mesh and Temperature Results for Load Step 2

Our task now is to calculate the temperature in one of these fins with more accuracy.  We will use a finer mesh and also add fillets between the fin and base.  For this example, I isolated one fin in ANSYS DesignModeler, did some slicing, and added a fillet on either side of the base of the fin of interest.

thermal-submodeling-5

Figure 5 – Fine Model (Submodel) Isolated Fin Geometry and Mesh, Including Fillets at Base

 

ANSYS requires that the submodel lie in the exact geometric position as it would in the coarse model, so it's a good idea to overlay our fine model geometry onto the coarse model to verify the positioning.

thermal-submodeling-6

Figure 6 – Submodel and Coarse Model Overlaid

thermal-submodeling-7

Figure 7 – Submodel and Coarse Model Overlaid, Showing Addition of Fillet

The next step is to insert the submodel geometry as a stand-alone geometry block in the Project Schematic which already contains the coarse model, as shown in figure 8.  A new Steady-State Thermal analysis is then dragged and dropped onto the geometry block containing the submodel geometry.

thermal-submodeling-8

Figure 8 – Submodel Geometry Added to Project Schematic, New Steady-State Thermal System Dragged and Dropped onto Submodel Geometry

 

Next, we drag and drop the Engineering Data cell from the coarse model to the Engineering Data cell in the submodel block.  This will establish a link so that the material properties will be shared.

thermal-submodeling-9

Figure 9 – Drag and Drop Engineering Data from Coarse Model to Submodel

The final needed link is established by dragging and dropping the Solution cell from the coarse model onto the Setup cell in the submodel.  This step causes ANSYS to recognize that we are performing submodeling, and in fact this will cause a Submodeling branch to appear in the outline tree in the Mechanical window for the submodel.

thermal-submodeling-10

Figure 10 – Solution Cell Dragged and Dropped from Coarse Model to Submodel Setup Cell

After opening the Mechanical editor for the submodel block, we can see that the Submodeling branch has automatically been added to the tree.

thermal-submodeling-11

Figure 11 – Submodeling Branch Automatically Added to Outline Tree

After meshing the submodel I specified that all three load steps should have their temperature data mapped to the submodel from the coarse model.  This was done in the Details view for the Imported Temperature branch, by setting Source Time to All.

thermal-submodeling-12

Figure 12 – Set Imported Temperature Source Time to All to Ensure All Loads Steps Are Mapped

Next I selected the four faces that make up the cut boundaries in the submodel and applied those to the geometry selection for Imported Temperature.

thermal-submodeling-13

Figure 13 – Cut Boundary Faces Selected for Imported Temperature

 

As mentioned above, the Imported Temperature details were set to read in all load steps by setting Source Time to All.  The Imported Temperature branch can now be right-clicked and the resulting imported temperatures viewed.  I also inserted a Validation branch which we will look at after solving.

thermal-submodeling-14

Figure 14 – Setting Source Time to All, Viewing Imported Temperature on Submodel

Any other loads that need to be applied to the submodel are added as well.  For this model, it's convection on the large faces of the fin that are exposed to ambient air.

thermal-submodeling-15

Figure 15 – Submodel Convection Load on Fin Exposed Faces

Since there are three load steps in the coarse model and we told ANSYS to map results from all time points, I set the number of steps to three in Analysis Settings, then solved the submodel.  Results are available for all three load steps.

thermal-submodeling-16

Figure 16 – Submodel Temperature Results for Step 2 (Highest Heat Flux Value in Coarse Model)

Regarding the Validation item under the Imported Temperature branch, this is probably best added after the solution is done.  In my case I had to clear it and recalculate it.  Validation can display either an absolute or relative (percent difference) plot on the nodes at which loads were imported.  Figure 17 shows the relative difference plot, which maxes out at about 6%.  The validation information as well as mapping techniques are described in the ANSYS Help.

thermal-submodeling-17

Figure 17 – Submodel Imported Temperature Validation Plot – Percent Difference on Mapped Nodes

Looking at the coarse model and submodel results side by side, we see good agreement in the calculated temperatures.  The temperature in the fillets shows a nice, smooth gradient.

thermal-submodeling-18

Figure 18 – Coarse and Submodel Temperature Results Showing Good Agreement

Hopefully this explanation will be helpful to you if you have a need to perform submodeling in a thermal simulation in ANSYS.  There is a Thermal Submodeling Workflow section in the ANSYS 15.0 Help in the Mechanical User's Guide that you may find helpful as well.

 

 

 

Serial and Parallel ANSYS Mechanical APDL Simulations

ANSYS-APDL-Macro-PeDALThere are times when you want to study the effects of varying parameters.  If you have an existing MAPDL script that is parameterized, the following procedure will allow you to easily run many variations in an organized manner. 

Let’s assume a parameterized MAPDL macro called build_solve that does something you want to simulate many times and has 2 variables called power and scale which are set with argument 1 and 2 respectively.  Running this macro with the classic interface, with power=30 and scale=2.5 would look like this:

build_solve,30,2.5

Next, create a MAPDL macro to launch all of the simulations.  This script could be named control.mac.  The first thing to do here is to create arrays of your parameters and assign values to them.  This example will vary power and scale.  Here are the arrays of values that will be passed to build_solve:

*dim,power,array,4

power(1)=10,20,40,80

*dim,scale,array,6

scale(1)=1,2,3,5,10,20

Most of the control.mac commands will be put inside of nested *do loops.  There will be a *do loop for each of parameters being varied.

*do,ii,1,4

*do,jj,1,6

Next, use *cfopen to set up the arguments to be passed to build_solve.  Each time through the *do loops will create a new run1.mac

*cfopen,run1,mac

  a=power(ii)

  b=scale(jj)

  *vwrite,a,b

  build_solve,%G,%G

*cfclose

One of the key features of this approach is to run anywhere and build directories below the working directory.  Use the /inquire command to store the current directory name.

/INQUIRE,dir_,DIRECTORY

Use *cfopen to create a string that will be used for the directory name.  By using the variables as part of the string, the directories will have unique names.  A time or date stamp could also be included in this string.  This macro is executed immediately to create the string dirnam for use in the commands subsequently.

*dim,power,array,4

*cfopen,temp1,mac

*vwrite,a,b

dirnam='power_%G_scale_%G'

*cfclose

/input,temp1,mac

Eventually, the resulting directory structure will look something like the image below.  Each directory will contain a separate simulation with the arguments of power and scale set respectively.

mapdl-script-automation

The last *cfopen creates a windows batch file which will (when executed)

  1. Create the new directory

  2. Copy all of the macro files from the working directory into the new directory (including run1.mac)

  3. Change into the new directory using CD

  4. Launch ansys in batch mode, in this case using a gpu and 12 cpus, using the run1.mac input and outputting to f.out

  5. Change back to the working directory (ready to do it all again)

The code for the windows batch file is:

*cfopen,rfile,bat

*vwrite,dir_(1),dirnam

MKDIR "%C\%S"

*vwrite,dir_(1),dirnam

COPY *.mac "%C\%S"

*vwrite,dir_(1),dirnam

CD "%C\%S"

*vwrite,

"C:\Program Files\ANSYS Inc\v150\ansys\bin\winx64\ansys150" -b -acc nvidia -np 12 -i run1.mac -o f.out

*vwrite,dir_(1)

CD "%C"

*cfclose

The last step is to run the windows batch file.  /sys is used to make this system call.  If the simulation is not well parallelized and you have enough licenses available, run the simulations in low priority mode immediately.  This will launch all of your simulations in parallel:

  • /sys,start /b /low rfile.bat

If the model is well parallelized (in other words, it will use your system’s gpu/cpus/RAM efficiently) or you only have 1 license available, launch the batch files in high priority mode and use the /wait option which will insure that windows waits for the job to finish before launching the next simulation.

  • /sys,start /b /high /wait rfile.bat

You can download and view the examples control.mac and build_solve.mac from this zip file: build_solve-control-macros.zip

ANSYS 2015 Hall of Fame Announced – Los Alamos National Labs and SynCardia Models are Finalists

2015-hall-of-fame-header-closed

Every year for a while now ANSYS, Inc. has chosen models made by users of the ANSYS software tools for their Hall of Fame.  This year had some very cool models across CFD, Structural, and Electromagnetic – including some great Multiphysics applications. Visit the ANSYS website to see all the winners here.

The three commercial winers of "Best in Show" were varied but powerful examples of how simulation can be used to improve performance and reliability of products:

 best-in-show-2015-ansys-hall-of-fame

Andritz Hydro used ANSYS Mechanical to model their assemblies to see if replacing welds with bolted joints would reduce weight and cost while keeping reliability.  They used sub-modeling, bolted joints, and contact.  

BRP used ANSSY CFX, ICEM CFD, and Mechanical to capture the forces caused by cavitation on their outboard marine engine. This engine pushes a boat at 75MPH (!!!) through the water, so yes, they get cavitation.  They used ICEM CFD for meshing, CFX to predict the cavitation and capture the cavitation loading, and Mechanical to see how the loading impacted the gear train and shafts. They were able to obitmize the desgin quickly using this process.

Spinologics used ANSYS Mechanical APDL to model the process of using a rod to straighten a deformed spine (scoliosis). They use the scriptability of the APDL to automate the creation of the models.  Very cool stuff.  Check out the video on the link.

We also want to mention two customers that were involved as Finalists.  

syncardia-heartSynCardia is often mentioned in this blog because, well, they make a frick'n artificial heart that saves lives every day.  We modeled an early iteration on the heart as a multiphysic problem probobly 5 or 6 years ago, it could have been longer ago. More recently Stony Brook University and the University of Arizona did a much more detailed model in ANSYS Fluent that looks at not just pressure and velocity, but Platelet dispersion patterns in the artificial heart.  Check out the video here:  https://storage.ansys.com/hof/2015/video/2015-stonybrook.mp4

2015-lanl-bgLos Alamos National Labs is another long time PADT customer and we were fortunate enough to be involved in the study that was recognized as a finalist. They used ANSYS Fluent to model something called vortex-induced motion or VIM in off-shore oil rigs.  Basically waves hit the platform and create these big swirling vortices.  These in turn put loads on the structure that can sometimes be very large.  The purpose of this study was to find a way to accurate predict VIM with simulation so they could then evaluate various solutions. A true Fluid-Solid Interaction (FSI) and because of the size of the structures and all that turbulence, High Performance Computing (HPC) problem. We hope to publish a paper on some related work this year… watch this space for more.

 This competition is a great way to see what others are doing, and if you submit your models, to show off what you have done.  Contact your ANSYS rep to learn more or drop us a note.

 

ANSYS Icepak: Diverging Residuals, Find and Fix the Problem!

Over the past week I have found myself dealing with a stubborn natural convection ANSYS Icepak model with convergence plots that would have been more aptly named divergence plots that looked like this:

pic2

In this post I’m going to show you the process I went through to find and fix my problem.

First, a few things to know about Icepak:

  • Many of the problems associated with your Icepak model are very likely mesh related.

  • If the bad elements are in a solid, you are probably OK, but if they are in the fluid, watch out!!

So, what is the conclusion? I have a mesh problem.

Second, how do you find the problem?

According to the above “convergence” plot, the continuity equation is diverging (or to my frustrated, on-a-deadline mind, it was GOING CRAZY). Well, a diverging continuity equation indicates that I have a conservation of mass problem. After consulting with one of my more experienced colleagues, Clinton Smith, he suggested that I do the following to work towards pin-pointing the problem:

  • Plot the gravity direction velocity (in my case, this was Uy)

  • Look for the Minimum and Maximum Uy locations in the model

Plotting Uy along a cut plane produced this:

ansys-icepack-diverging-residuals-3

ansys-icepack-diverging-residuals-4

As Clinton thought, plotting Uy instantly showed me the section of my model that was producing un-physical results. Next, I looked for the maximum and minimum velocity locations because this would further show me problems.

ansys-icepack-diverging-residuals-6

ansys-icepack-diverging-residuals-5

Next, I need to determine why this area of my model is the problem. Like I said above, it is likely a mesh problem. In the Mesh Control panel under the Quality tab checking the Face alignment values often help to locate very bad elements:

ansys-icepack-diverging-residuals-7

Clicking on the pink block above displays the elements in the graphics window and it was instantly obvious that my problem was due to distorted elements in my area of interest:

ansys-icepack-diverging-residuals-8

ansys-icepack-diverging-residuals-9

When I look at these elements with a perspective of my model geometry I see that the elements are obviously in the fluid domain:

ansys-icepack-diverging-residuals-10

ansys-icepack-diverging-residuals-11

I have found my problem.

Third, how do I fix the problem? Well, the location of my bad elements happens to lie on a CAD body in Icepak. This means that I am limited in my ability to control the mesh on the actual body. So, though there are likely multiple ways that this problem could be solved, I had the idea to create an air block in the area above that I could much more easily control from a meshing perspective. Having a real Icepak primitive in that space would force the mesher to conform to the boundary of the CAD body.

ansys-icepack-diverging-residuals-12

Like I thought, the air block worked!

ansys-icepack-diverging-residuals-13

I should note that in order to get the mesh to conform exactly, I had to put the air block into its own meshed-separately assembly. And now my residuals look much better!

ansys-icepack-diverging-residuals-14

Summary:

  • Diverging continuity residuals indicate a conservation of mass problem

  • Plot velocities to locate problem region

  • Plot min/max velocity to further identify problem

  • If bad elements are in the fluid region, they must be fixed

  • Consider creating an air block in the region of interest to more finely control the mesh

Configuring Laptop “Switchable” Graphics for ANSYS Applications

IMG_4894

A lot of laptops these days come with “switchable” graphics.  The idea is that you have a lower capability but also lower power consuming ‘basic’ graphics device in addition to a higher performing but higher power demand graphics device.  By only using the higher performance graphics device when it’s needed, you can maximize the use time of a battery charge. 

A lot of the ANSYS graphics-intensive applications may need the higher end graphics device to display and run correctly.  In this article, we’ll focus on the AMD Firepro as the “higher end” graphics, with Intel HD graphics as the “lower end”.  We will show you how to switch to the AMD card to get around problems or errors in displaying ANSYS user interface windows.

The first step is to identify the small red dot graphics icon at the lower right in the task bar:

fix_laptop_graphics_ansys-01

Figure 1 – AMD Catalyst Icon

 

Next, right click on the icon to bring up the AMD Catalyst Control Center, if you don’t see the switchable option as shown two images down.

fix_laptop_graphics_ansys-02

Figure 2 – AMD Catalyst Control Center Right Click Menu Pick

 

Right click on the same icon again, if needed to select “Configure Switchable Graphics,” as shown here:

fix_laptop_graphics_ansys-03

Figure 3 – Select “Configure Switchable Graphics” via Right Click on the Same Icon

 

In the resulting AMD Catalyst Control Center window, click on the Add Application button.

fix_laptop_graphics_ansys-04

Figure 4 – AMD Catalyst Control Center Window

Next browse to the application that needs the higher end graphics capability.  This might take a little trial and error if you don’t know the exact application.  Here we select ANSYS CFD-Post and click Open.

fix_laptop_graphics_ansys-05

Figure 5 – Selecting appropriate executable for switchable graphics

Finally, select the High Performance option from the dropdown for your chosen executable, then click the Apply button.

fix_laptop_graphics_ansys-06

This should get your graphics working properly.  Again, the reason we have the two graphics choices is to allow us to better control power consumption based on the level of graphics that are needed per application.  Hopefully this article helps you to choose the proper graphics settings so that your ANSYS tools behave nicely on your laptop.

Getting to know ANSYS – SIwave

This video is an introduction to ANSYS SIwave – an analysis tool for Integrated Circuits and PCBs

ANSYS Workbench Installations and RedHat 6.6 – Error and Workaround

penguin_shWe were recently alerted by a customer that there is apparently a conflict with ANSYS installations if Red Hat Enterprise Linux 6.6 (RHEL 6.6) is installed. We have confirmed this here at PADT. This effects several versions of ANSYS, including 15.0.7, 14.5, and 14.0. The primary problem seems to be with meshing in the Mechanical or Meshing window.

The windows errors encountered can be: “A software execution error occurred inside the mesher. The process suffered an unhandled exception or ran out of usable memory.” or “an inter-process communication error occurred while communicating with the MESHER module.”

The error message popup can look like this:
th1

or
th2

th3
Note that the Platform Support page on the ANSYS website does not list RHEL 6.6 as supported. RHEL is only supported up through 6.5 for ANSYS 15.0. This is the link to that page on the ANSYS website:

http://www.ansys.com/staticassets/ANSYS/staticassets/support/r150-platform-support-by-application.pdf

That all being said, there is a workaround that should allow you to continue using ANSYS Workbench with RHEL 6.6 if you encounter the error. It involves renaming a directory in the installation path:

In this directory:

/ansys_inc/v150/commonfiles/MainWin/linx64/mw/lib-amd64-linux/

Rename the folder ‘X11’ to ‘Old-X11’

After that change, you should be able to successfully complete meshes, etc,. in ANSYS Workbench. Keep in mind that RHEL 6.6 is not officially supported by ANSYS, Inc. and their recommendation is always to stick with supported levels of operating systems. These are always listed in the ANSYS Help for the particular version you are running as well as at the link shown above.

Since the renamed directory is contained within the ANSYS installation files, it is believed that this will not affect anything else other than ANSYS. Use at your own risk, however. Should you encounter one of more of the errors listed above, we hope this article has provided useful information to keep your ANSYS installations up and running.