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Flow Simulation

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I thought I'd just post some additions to inform you all of the Simulation software that the developers have snuck into SP's of 2012.  Thanks to my friends and colleagues, Delphine G. & Omar Z. for providing me with these details.


I think you'll agree that I always look forward to the What's New every year.  What's even cooler is when you get gifts like these after the initial release.  It's like Xmas in July!


Simulation 2012 SP2 (not verified yet by yours truly, um just simply not enough time in the day)

  1. In NL, plot reaction or contact forces vs time
  2. In NL, select a time value instead of a step to view results
  3. In NL, plot contact contours, not just vectors
  4. In NL, animate contact contour and vector plots


Flow Sim 2012 SP1 (same disclaimer as above)

  1. Improved solution-adaptive meshing technology (SP1). The improved refinement technology improves the quality of the computational mesh in the high-gradient flow regions in case solution-adaptive refinement is involved.


Flow Sim 2012 SP2 (ditto)

  1. Chinese UI and Help.
  2. Improved fan model. The new model offers better convergence and less oscillations at the beginning of the calculation.
  3. Record video. Now you can record screen activities as an animation file
  4. Improved definition of Electrical Condition. Now the specified electrical resistance is applied to the exact area of contacts between conductive solids.
  5. Export materials and connection to external databases. Now you can export desired material from Engineering Database to XML files.
  6. Tutorial for Tracer Study


Copyright © 2012 Dassault Systèmes SolidWorks Corp. All rights reserved.
Do not distribute or reproduce without the written consent of Dassault Systèmes SolidWorks Corp.

Adapted from an email that I sent out to a client:

I will give you my opinion on a good starting machine for doing pretty much any Flow Simulation.  I can say this because I have worked with a number of customers over my 8+ years at SolidWorks.  Note that any computer purchase (if one were to happen for you), that upgradeability (especially on RAM) of the system should be high in your considerations for future-proofing.


I would recommend going with a Quad core Intel i7 processor, which is the latest technology in CPUs from Intel; faster CPU speeds are preferable but the fastest speed chips come at a premium… economically speaking, one step below fastest or mid-range speeds are fine and money is better spent on more RAM.  Dual-core CPUs are OK.  If you can go for dual Quad cores, go for it.  With any processors today, typically hyperthreading is enabled by default, my recommendation is to disable hyperthreading in the BIOS.


More RAM is better as implied earlier.  I’d go with 8GB to start, and upgradeable to 16GB or more; 4GB is OK as a start.  Obviously you’ll need a 64-bit OS to take advantage of the additional RAM, so Win7 64-bit is best moving forward; WinXP 64-bit is OK (for now).


A big bottleneck that many people do not consider is reading and writing data to hard drive, especially larger file sizes created by analysis.  Laptops now offer SSDs which is where I would recommend customers to go, but again they come at a premium per GB.  If SSD is not on your plates for now, then get the speediest spinning HDD available; laptop HDDs are not as speedy as desktop ones.  If traditional HDD on a desktop, also consider RAID10 for speed and mirrored redundancy… requires 4 identical HDDs.


Video card is not a big requirement for the analysis side of things, but recommendations are to go with a SW approved graphics card (workstation grade, i.e OpenGL) & driver.  Let design side of modeling determine what graphics card to use.


Hope this info helps!  Attached find a WMV capturing the Intel CPU Performance gadget of my machine running a Flow Sim problem with 3.2 million cells.


Copyright © 2011 Dassault Systèmes SolidWorks Corp. All rights reserved.
Do not distribute or reproduce without the written consent of Dassault Systèmes SolidWorks Corp.

More than one person has told me that we should rename SolidWorks Flow Simulation to SolidWorks Flow and Thermal Simulation, because (a) it does a lot more than just flow calculations and (b) it is the best design tool to use for thermal simulation especially when convection is involved.  I'll have to agree with them solely for the fact that it would make my job a little bit easier.


Temperature plays such a large role in fluid dynamics that you cannot uncouple it from the solution; a great example in point is any material property, such as density and viscosity, that are very temperature dependent.  The change in density due to heating and cooling is what drives the flow in natural convection.  Thus you have air (or the environmental fluid) moving and convection is going on everywhere all the time, with the exception of when a body is sitting in a vacuum where there is no environmental fluid.


The convective heat transfer rate also varies widely over a given surface because it depends on many factors, such as: geometry, orientation to gravity, temperature of solid and fluid, material of solid and the type of surrounding fluid, and velocity of the fluid.  If one trys to get a uniform averaged value over a surface, even with the best tables or hand calcs, it'll be a ballpark figure at best and assuming it to be uniform can neglect a lot of the physics.  SW Flow Simulation does the calculating and consideration of all these factors because it knows the geometry and the flow equation is applied to the 3 conservation methods: mass,  momentum, and energy (energy conservation being the thermal calculation part).  It takes longer to manually calculate the heat transfer coefficient for every surface in contact with the surrounding fluid, so we're all too lazy (and in this case rightfully so) to take the time to do this and hence just collectively apply a single value for many surfaces.


Consider this picture of a custom heat sink showing contours of convective heat transfer coefficient; could you get a good average heat transfer coefficient from this model?  I'll say no.




So in summary, SW Flow Simulation is the best tool for Thermal analysis because the correct handling of convection, both forced and free, is crucial in getting accurate results that best matches the physics of a real-world design.

After finishing the  calculation for an external flow problem, a great way to show the results is  with flow trajectories.  Since the computational domain usually is quite large  for external problems, this is not as straight-forward as for an internal flow  where one can choose either the inlet or outlet lid.  The best way to create  flow trajectories for an external flow problem (concentrating the flow lines  around the body) is by manually picking points on a plane.  I'll instruct you  how to do this later, but first some example pictures:




After you right click Flow Trajectories on the tree and choose Insert, you get the dialog box shown below.  Choose the second Starting Points option button for Picking Points that has XYZ on it.  In the blue box below that choose a Plane, and then orient the graphics window perpendicular to that plane and use the slider bar in the dialog box to position the plane to where you want it.  At this stage you can manually enter XYZ coordinates, but this is way too cumbersome to do many points, so instead select the Pick Points button that looks like an anchor (think of it as fixing that plane).  Now orient the graphics window normal to the body, and then start graphically picking points just around the body (see the selected points in the pictures at bottom).  As you move your cursor around the values in the now grayed out XYZ boxes will change to reflect your cursor position on the screen.  You have additional options of replacing, deleting individual or deleting all points.  The remaining options for flow trajectories below this section are the same.  Finally, click the green checkmark for OK.






Copyright © 2010 Dassault Systèmes  SolidWorks Corp. All rights reserved.
Do not distribute or reproduce without  the written consent of Dassault Systèmes SolidWorks Corp.

In this Flow example, I have an inlet pipe diameter 2 times larger than its corresponding outlet pipe diameter with a turbulent flow rate.  Below is a descriptive picture of this pipe with two different configurations: (A) at a small angle of 3°, which causes a very long transition, and (B) a larger angle of 30° resulting in a short fitting.

Pipe A

Pipe B


Which configuration results in a smaller, thus better, pressure drop?  Better yet, what is the best angle to reduce the pressure drop to a minimum.  It is very easy with configurations (or a design table) to create a fitting with a transitional angle at every degree from 3 to 30.  We can leverage these configurations within SW Flow Simulation with Cloning and Batch Runs to complete the task.

What we find out is that the best angle is 11°, as shown in the graph of the results below (only values until 13 are shown).  This is because if the angle is too small, then the overall pipe length is longer resulting in frictional pressure losses.  Larger angles creates a sharp velocity increase and the resulting pressure drop goes up.  Isn't this a perfect reason to use a virtual test bench to find out what the best design is without spending the money and taking the time to build the physical test!


Could I have done this same task with the Parametric Study tool in Flow Simulation?  Not exactly, that tools requires that you have a set value defined by a Goal that you are hoping to converge upon, thus the Parametric Study tool is not an optimization tool.


Copyright © 2010 Dassault Systèmes  SolidWorks Corp. All rights reserved.
Do not distribute or reproduce without  the written consent of Dassault Systèmes SolidWorks Corp.

SLPM is the unit that a gas flow meter reads, but even though it appears to be a volume flow rate, it is in fact a mass flow rate.  It is nonsense to report the SLPM at equivalent standard (or STP) conditions (0°C or 273.15K and  1atm) without also noting the pressure and temperature for the reference condition.  I have a conversion spreadsheet that you can also use in cases where someone gives you a gas flow rate at standard conditions. You can download the spreadsheet from here: (5.66 KB)


The second tab of the spreadsheet has the molecular mass for different gas mixtures that you can use to populate the "Mole Mass" column on the first sheet.


On the main tab, you insert values in the  white columns and the calculated values are in yellow columns.  Insert the reference temperature (in °C) and pressure (in atm), and then finally put in the stated SLPM for the gas flow, and you will get the mass flow rate to be used in kg/s.


Copyright © 2010 Dassault Systèmes  SolidWorks Corp. All rights reserved.
Do not distribute or reproduce without  the written consent of Dassault Systèmes SolidWorks Corp.

Here's a few new Flow Simulation Post-Processing Tips that may help you out in creating both meaningful and exciting result plots.

Have you ever had problems with showing Surface Plots, where it basically shows none of the surfaces that you selected; an example of this is given below:



If you make a simple change to the definition of the Surface Plot, by adding the Offset option.



You will get the expected results, as shown below:



To get the same Flow Trajectory animations as shown in the following YouTube videos:
or this one...

Create a new flow trajectory, with spheres and a large density (1,000 or more), on the plane parallel to the flow direction, and slide the plane just before the solid body.



Create an animation, click on More, and then right-click the magenta line and choose Properties.

Set the impulse to restart every 0.5 sec (or whatever looks best).



A few thanks goes to Dolf Broekaart, Manager of Simulation from VAR Design Solutions out of the Netherlands, who showed me some great new ways to make use of the flow trajectory animations.  Thanks Dolf!


Copyright © 2010 Dassault Systèmes SolidWorks Corp. All rights  reserved.
Do not distribute or reproduce without the written consent of  Dassault Systèmes SolidWorks Corp.

I frequently tell people that SolidWorks Flow Simulation is a well documented program.  If you are using this simulation tool, you will want to have easy access to three important PDF document files, these are: (1) Solving Engineering Problems, (2) Technical Reference and (3) Tutorials.  The files are copied to your hard drive when the software is installed, and you may not have known that they are there.

First how to create the shortcut.  Find the location of the folder where they reside; in my installation they are located at: C:\Program Files\SolidWorks Corp\SolidWorks Flow Simulation\lang\english\Docs which I think would be the typical location for the English language version.  You can also find them through windows by doing a search for one of the documents, such as "solvingengineeringproblems.pdf".  Open that file's folder location via a right-click menu on that filename and choosing "Open containing folder."

To create a shortcut to that file, right-click the file and then select "Create Shortcut."  Another way to create a shortcut directly on your desktop is to right-click on the file and choose: Send To > Desktop (create shortcut).  Next, my preference is to rename the shortcut to make it more descriptive to me and remove any unnecessary words such as "Shortcut to" (I already know that's what it is).

Finally to finish up, I like to place this shortcut in the Start Menu list.  To do this, simply left-click and hold the shortcut link file, drag it over to the Start Menu in the bottom left, hover there until it opens the list, then drag over to Programs and hover there too, and do this same thing until to can drop it into the program folder where you want, such as in the SolidWorks Tools folder.  (I actually create a different new programs folder within the SolidWorks one just for all my Simulation stuff.  If you know how to do this, very easy, go ahead and do that too).

So what is contained in these documents:

(1) Solving Engineering Problems

Strategies for using Flow Simulation to solve real world problems.  Advanced knowledge on such topics as meshing, calculation control and flow freezing (or FF) (FF is a tool to help speed up a thermal-convection conjugate problem).  Also a guide to some other advanced features that not everyone would run into for their problems, such as cavitation, steam, humidity and real gases (instead of the default ideal gas law).  Example problems are given.

(2) Technical Reference

All the detailed info for someone wanting to know how the program solves the Navier-Stokes equation.  Physical capabilities, governing equations and numerical solution techniques are some chapters of this document.  The document also includes 23 validation examples showing Flow Simulation predictions against either theoretical or experimental data.  References to publications for these problems are provided.  The unsolved fully-setup model files are located at (typical installation): C:\Program Files\SolidWorks Corp\SolidWorks Flow Simulation\Validation Examples

(3) Tutorials

Before you get started using the program and even before going to on-site training.  It is highly recommended to go through a few of the 13 tutorial examples in this document.  Start with one of the first three (the ones prefixed "First Steps") to learn the interface before moving onto another one that is of interest to you.  The model files are located at (typical installation): C:\Program Files\SolidWorks Corp\SolidWorks Flow Simulation\Examples


Copyright © 2009 Dassault Systèmes SolidWorks Corp. All rights reserved.
Do not distribute or reproduce without the written consent of Dassault Systèmes SolidWorks Corp.

To spruce up the trajectory animations in Flow Simulation, here are a few things that you can do:

1) Turn on the Lighting effects (see below pics).  On the left, without lighting; on the right, with lighting on.  Locate the Apply Lighting button on the far right of the toolbar on the FloWorks tab.  (Bonus tip: To turn Lighting on by default, on the SolidWorks drop-down menu click Tools > Options, then click the Third-Party button at the bottom and in the dialog that opens scroll down to View Options and the fourth one from the bottom of this section is Apply Lighting (default).)



2) Impulse the trajectories.  After you create the animation, click on the More button on the animation toolbar, right-click on the flow trajectory timeline (colored purple to mean that it will launch), change the Restart time to a non-zero value by clicking the up button once.  When it plays it will impulse the flow from the inlet, which makes for a more dramatic animation.
Note: To play the animated GIF below, click on the picture.


3) Change the View orientation.  Just like you do with SW animator, change the view orientation by a right-click on the assembly (or part) name to turn off the lock orientation.  Create a control point at the beginning of the timeline, move the vertical time bar to a new time and then simply move and rotate the model, a new control point will automatically be created.  Now when you play, the model will gradually change its orientation from one control point to the next.

Here's a tweak for Flow Simulation to use when you want to create nice flow trajectory images for reports, publishing, or marketing, especially for close ups.

You can adjust the image quality of the flow trajectories by the following procedure:

In SolidWorks (with Flow Simulation add-in active), go to Tools > Options > click on the Third Party button at the bottom.  Scroll down to the section called "View Options" and locate the field for "Trajectory image quality."

Trajectory image quality allows you to adjust the quality of rendering of 3D pipes, arrows or spheres that are used to visualize flow and particle trajectories. You can change the value of Trajectory image quality in the range from 1 to 100, the bigger the value, the higher the quality of the 3D trajectories visualization. The default value is 10. Please note that high values can result in a significant increase in CPU time required to build the trajectories, especially in the case when the number of trajectories is also high.

Here is a chart to see exactly what changes the image quality value has on the rendering.

A quality of 1 makes a obviously faceted rendering, 10 is a little better and 100 is very smooth.  Not shown on the chart, I did not see much difference between the image quality for 50 and 100 except with the reflection of light.  Pipes show the least effect of image quality except for shininess and appearing slightly larger.


Copyright © 2009 Dassault Systèmes SolidWorks Corp. All rights reserved.
Do not distribute or reproduce without the written consent of Dassault Systèmes SolidWorks Corp.
A good way to show flow trajectories is by combining an  animation of arrows with pipes resulting in the below example animation.  When  animating the type called "Lines with arrows," it acts like an animation with pipes where they start from the beginning and go to the end; that's not the result that I am looking for.  But with the  new combination, the pipes stay static and the arrows move on top of the  pipes.

To accomplish this,  just simple create a flow trajectory plot with "Arrows" (flat arrows also work  well).  Set the size of the arrow appropriately, in my example I used a 2mm  arrow size.  Clone that flow trajectory plot and then edit the type to "Pipes" and make the size about 4 times smaller, so in my example the pipe size is  0.5mm.  Then just animate the first flow trajectory plot with the Arrows, so that the one with the Pipes stays static.


Animated 3D arrows with static pipes.gif
Copyright © 2009 Dassault Systèmes SolidWorks Corp. All rights reserved.
Do not distribute or reproduce without the written consent of Dassault Systèmes SolidWorks Corp.
Since the movie on Amelia Earhart started this past weekend, it reminded me of another historical figure in aeronautics, Henri CoandăThe point of this post: SW Flow Simulation supports the Coandă effect.

The Coandă effect is the tendency of a fluid jet to stay attached to an adjacent curved surface that is very well shaped.  The principle was named after Romanian Henri Coandă, who was the first to recognize the practical application of the  phenomenon in aircraft development.

More  info:
Copyright © 2009 Dassault Systèmes SolidWorks Corp. All rights reserved.
Do not distribute or reproduce without the written consent of Dassault Systèmes SolidWorks Corp.