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Showing results 1 to 12 of 12 Search took 0.00 seconds. Search: Posts Made By: ghorrocks

Forum: CFX May 2, 2013, 18:48

Replies: 33 cyclone separator particle tracking prob.. Views: 7,447 Posted By ghorrocks The SGS models in LES are generally based on the... The SGS models in LES are generally based on the assumption (which is generally a good assumption) that all the anisotropy in turbulence resides in the largest turbulence scales and the small scale...

Forum: CFX May 2, 2013, 02:23

Replies: 33 cyclone separator particle tracking prob.. Views: 7,447 Posted By ghorrocks CEL cannot calculate anything in time, so you are... CEL cannot calculate anything in time, so you are either going to have to do this in post processing or write your own user fortran to do it (and that will not be easy). When I did this previously...

Forum: CFX May 2, 2013, 00:41

Replies: 33 cyclone separator particle tracking prob.. Views: 7,447 Posted By ghorrocks You have to define all these variables as CEL... You have to define all these variables as CEL expressions. The tricky one is the u' terms - are you doing spatial or temporal averaging to obtain them? Neither of these are easy to implement in CEL.

Forum: CFX May 1, 2013, 20:59

Replies: 33 cyclone separator particle tracking prob.. Views: 7,447 Posted By ghorrocks The key check for an LES model that your mesh and... The key check for an LES model that your mesh and timescales are adequately resolved is to plot the turbulence power spectrum (intensity versus frequency, eg...

Forum: CFX April 20, 2013, 07:47

Replies: 33 cyclone separator particle tracking prob.. Views: 7,447 Posted By ghorrocks If the Smagorinsky SGS model is used in LES with... If the Smagorinsky SGS model is used in LES with a mesh which is grossly too large then the SGS viscosity goes very high (the SGS viscosity is proportional to mesh length scale squared see eqn 2-161...

Forum: CFX April 20, 2013, 07:34

Replies: 33 cyclone separator particle tracking prob.. Views: 7,447 Posted By ghorrocks Hi Sakura, I think you are misunderstanding... Hi Sakura, I think you are misunderstanding what OJ and I are saying about mesh density. We are not talking about the mesh density tool in ICEM. Imagine you have a 1m cube region you are meshing....

Forum: CFX April 19, 2013, 06:09

Replies: 33 cyclone separator particle tracking prob.. Views: 7,447 Posted By ghorrocks LES requires a lot of additional checks and care... LES requires a lot of additional checks and care or the results will be rubbish. You will need to refer to a turbulence modelling textbook such as Turbulence modelling for CFD by Wilcox for details....

Forum: CFX April 18, 2013, 18:47

Replies: 33 cyclone separator particle tracking prob.. Views: 7,447 Posted By ghorrocks LES is very mesh sensitive and requires a MUCH... LES is very mesh sensitive and requires a MUCH finer mesh than SST or RSM. You will need to do a very careful mesh sensitivity study to be confident you are accurate. And I agree with OJ, I would...

Forum: CFX April 18, 2013, 07:21

Replies: 33 cyclone separator particle tracking prob.. Views: 7,447 Posted By ghorrocks Are you sure 3s run time is enough to create the... Are you sure 3s run time is enough to create the central vortex which does the separation? Why do you say your mesh is OK? How did you check? Why have you limited it to 1-3 coeff loops per...

Forum: CFX April 18, 2013, 06:33

Replies: 33 cyclone separator particle tracking prob.. Views: 7,447 Posted By ghorrocks I still don't understand what you are trying to... I still don't understand what you are trying to do but I will ahve a guess. It seems like you need an outlet on the bottom to allow the large particles to exit, as expected. But you seem to be saying...

Forum: CFX April 17, 2013, 18:43

Replies: 33 cyclone separator particle tracking prob.. Views: 7,447 Posted By ghorrocks Sorry I do not understand your question. Can you... Sorry I do not understand your question. Can you explain it more?

Forum: CFX April 17, 2013, 08:02

Replies: 33 cyclone separator particle tracking prob.. Views: 7,447 Posted By ghorrocks FAQ:... FAQ: http://www.cfd-online.com/Wiki/Ansys_FAQ#Why_are_my_results_inaccurate.3F

Showing results 1 to 12 of 12

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