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Kinetic Energy in CFD
Posted 13.08.2021, 16:22 GMT-4 Computational Fluid Dynamics (CFD), Results & Visualization 1 Reply
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Doesnt look like COMSOL outputs kinetic energy automatically. I've had to postprocess the results to get KE. Specifically, I do a volume integration of rho v^2 over all my stored timesteps in Derived Values - Volume integration. This takes a long time! Does anyone have a faster way to get kinetic energy from a transient CFD calculation?
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David,
yes complex post processing in Comsol can be painstakingly slow. One workaround I sometimes use is doing the integration using an intop() operation during solving. I define a respective variable and I define a state variable pointing to this variable.
In my experience such integrations during solving do not noticeably increase the solution time. I assume during solving this runs in optimized C code while the post processing is based on slow interpreted Java code.
Using the state variable is key because only this way this variable becomes a part of the solution. Otherwise, if using the normal variable, the integration will be done in Java again. You don't need to run the solver again, update solution is sufficient after you defined it all.
State variables don't have a unit, you need to take care of that by yourself.
Hope it helps, cheers,
Edgar
-------------------Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com