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Large eddy simulation runtime.

Posted Nov 18, 2020, 6:58 a.m. EST Computational Fluid Dynamics (CFD), Cluster & Cloud Computing Version 5.5 2 Replies

Dan Bence
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Has anyone had experience of running Large Eddy Simulations ? I want to get a sense of how practical it is to run LES simulations in the COMSOL environment. I could not find any examples in the Application Libraries.

I would be grateful if you could share your experience of runtimes, number of elements etc.

Thanks, Dan.

2 Replies Last Post Jan 28, 2021, 10:26 a.m. EST
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Hello Dan Bence

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Sahrish Naqvi
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Posted: 4 years ago Jan 22, 2021, 12:38 p.m. EST

Hi Bence, I also looking for case set up, but could not find it. What about you?

Hi Bence, I also looking for case set up, but could not find it. What about you?
Frank van Gool
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Posted: 4 years ago Jan 28, 2021, 10:26 a.m. EST
Updated: 4 years ago Jan 29, 2021, 7:13 a.m. EST

I did a quick test with a building simulation, here I choose the following setup:
First realizable k-eps simulation stationary. With 200k elements, 15 minutes on a laptop then switch to LES, SMAGORINSKY
New transient study, initial values from previous simulation. Total length, 1 fluid pass = 300 sec Time step determined from CFL number:
Mesh size around building ±4m; free stream velocity 2 m/s
With a CFL of 0.5, the time step gets me to 1 sec
Solver: Generalized alpha timestepping, manual step of 1 sec. Disable initialisation Total runtime on laptop: 3 hours

The movie below gives some result of the vorticity
For a better results:
- > 2 fluid passes
- a finer mesh
- add turbulence to the inlet

It would be needed to implement an inlet condition based on turbulence, or COMSOL could release a method to deal with this, as in this example the inlet is perfectly smooth.

ps. this is my first test with it, and do not have previous experience in other software with this

I did a quick test with a building simulation, here I choose the following setup: First realizable k-eps simulation stationary. With 200k elements, 15 minutes on a laptop then switch to LES, SMAGORINSKY New transient study, initial values from previous simulation. Total length, 1 fluid pass = 300 sec Time step determined from CFL number: Mesh size around building ±4m; free stream velocity 2 m/s With a CFL of 0.5, the time step gets me to 1 sec Solver: Generalized alpha timestepping, manual step of 1 sec. Disable initialisation Total runtime on laptop: 3 hours The movie below gives some result of the vorticity For a better results: - > 2 fluid passes - a finer mesh - add turbulence to the inlet It would be needed to implement an inlet condition based on turbulence, or COMSOL could release a method to deal with this, as in this example the inlet is perfectly smooth. ps. this is my first test with it, and do not have previous experience in other software with this

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