Mega Strom Chasing with Autodesk CFD

by James Herzing16 May 2016

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We’ve already seen how we can quickly see some eternal flow results around simple geometry using Autodesk Flow Design in our Duck Dodgers of the  24th and a Half Century video (missed it? check it out here!), but what if we are interested in more detailed geometry and results other than velocity? That’s where Autodesk CFD comes into play. Used to optimize your design for improved flow through or around the parts, determine pressure drop across a system or verify thermal results and fluid/thermal interaction, CFD is the tool for you.

To demonstrate how to start to calculate results in an external flow analysis, we’ve called on our friend Mega Man to help us demonstrate. And it’s only fitting that the robot master Air Man be involved to add to the mix!

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As is normally the case, we start out in Fusion 360 to create our geometry.  Want my design to follow along? Grab it here from the Fusion Gallery. Saving the file as a .step and choosing a New analysis in Autodesk CFD, we’re greeted with a Geometry Tools dialog box. The first step is to click the Merge button to clean up features for improved mesh results, and then to click on the Ext. Volume tab. With this tab active, you will see a pink box surround your geometry, which represents the fluid volume. We’ll stretch out the box in all directions but past our characters feet to help ensure a fully developed flow profile.

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We now have to define material properties for the 3 parts. The external fluid is easy to do, as it is already set to Fluid with Air as the default, so just right clicking on it in the model tree and clicking Apply is enough. Selecting Mega Man, either by right clicking in the model tree or by choosing Edit and selecting him on the display screen will allow us to modify his material. Changing Type to Solid and the Name to Human, he will be defined. Repeat this process for Air Man, but choose Steel as the material Name.

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All that is left to do before analyzing is to define boundary conditions. Rotating the model to select the surface closest to Air Man, choose edit and select the surface. Change the Type to Velocity, the Unit to MPH and define a velocity of 85.  Rotate the model to the opposite side, choose Edit and the surface and define the Type to Pressure, Unit to PSI and Pressure to 0.  You’re now ready to press Solve!  Simple, wasn’t it? And the best part is, it is that easy for your external flow designs as well!

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In the results environment, we can now take a closer look at just how hard Air Man is blowing on Mega Man. Clicking on Plane and Add, we can create a cut plane to see our velocity profile. Click and drag the arrow on the cut plane until you can see the outline of Air man. Notice, the air velocity speeds up as it goes through the narrow fan area.

To get a better idea how the air is moving we can define seed points. In click on Traces and define your seed density to be 2.5 so that we don’t create too many and kill the machine. With a rectangular pattern chosen, click on the top left corner of the cut plane, the top right corner, and then the bottom right. This will give us a nice variety of points to look at.

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We’re able to change the units being displayed on the legend, as well as modify the minimum and maximum values to understand how fast the wind is blowing around Mega Man. Good thing his blaster doesn’t seem to be effected by the wind!  If you didn’t get a chance to see the video on this, or participate in the video game challenge, check it all out right here. 

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