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Hello everyone. 


I am currently running external aerodynamics flow simulations for a truck model. I use HyperMesh to generate the surface mesh and then use Virtual Wind Tunnel to run the flow simulation. 


Once the simulation is complete, VWT generates the automatic PDF report with a drag coefficient value. However, after performing design modifications to the geometry of the model, the drag coefficient values seem to be off from expectations. Hence, I am wondering if there is a way to manually calculate the drag force generated by the model in AcuFieldView, AcuConsole or AcuProbe and then the drag coefficient using the frontal area?. I want to check the validity of the drag coefficient values that are automatically generated in the report.


Also, I have noticed that the report calculates the drag for each and every part in the model and then sums it up to give the total drag value. I'm wondering if there is a way to select the entire model (all parts included) and display the drag force created by it rather than doing it for individual parts.


Thanks for the help in advance!


Yatish Chandra

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There are many things that need to be verified, including mesh dependence studies, to validate the results against tests/expectations. Have you tried different mesh sizes?



Yes its possible to get the drag values manually from the simulations as well.  The drag forces are available in AcuProbe for individual surfaces. Since there are many surfaces, you might want to use AcuSumOsi script. Check Program Reference Manual in your installation. That has details on how to use this command.


I would recommend contacting your local Altair Support to help you out with this issue and scripts that you might need.

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