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Turbulence Parameters

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Old   November 24, 2018, 08:05
Default Turbulence Parameters
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1) Can someone explain in easy words what is turbulence length and intensity for any turbulence model?
2) Do we have to set there values appropriately or leave them as default for any case?
3) Do they effect output variables or results?
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Old   November 24, 2018, 10:49
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With any turbulence model you solve transport equations for something to do with turbulence (for example, k and epsilon or k and omega). What you need to specify are the boundary conditions for k and epsilon or k and omega, etc.


1) These are lay-man's properties of turbulence and quite self-explanatory. See the wiki. It is an option provided for convenience. What you're really doing is specifying the BC's for k & epsilon/omega. These are some cute formulas used to convert from length and turbulence intensity into the actual variables used. Intensity and length scale are used because that's what you often calculate in an experiment.
2) You need to specify the correct values for your case. Again, you are specifying the BC's at boundaries (mostly inlets). I.e. the state of turbulence entering the domain at inlets.
3) Yes absolutely but your problem may be sensitive/insensitive to the BC's at inlet depending on what your problem actually is. If your goal is to get 100% accuracy turbulence everywhere in the domain, then you are shit out of luck. However, if you have a car that is placed 1km downstream from an inlet of a wind tunnel, then by the time the flow arrives at the car, it has pretty much forgotten the state of turbulence at the inlet and evolves into the natural state of the flow in the wind tunnel.
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Old   November 29, 2018, 11:58
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Thanks man! i appreciate your help and support whenever I post a query.
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