wallscale bulk

mach000 · April 1, 2010, 10:43

Hi to everybody,
i'm studying a multiphase problem.
During the simulation I have some informations about "wallscale bulk".

There is someone that could explain me the meaning of this parameters and how I can understand if it's all ok?

Thank you very much in advance

ghorrocks · April 2, 2010, 06:10

This is the solver working out the distance to walls for the SST turbulence model. As long as it converges a bit it should be fine. It is a very numerically stable solver (and simple mathematics) so rarely causes a problem.

mach000 · April 2, 2010, 06:46

HI,
thank you for your reply.

The problem is that at the beginning of the simulation I have "Failure" about wallscale bulk and consquently I have overflow.

It looks that with double precision simulation the run goes better...

ghorrocks · April 2, 2010, 07:02

This is quite rare, and yes, sometimes switching to double precision can fix it. Hopefully you are proud to have found such an unusual problem.

There are some settings which control it, I have never used them but I know they are there. You might be able to fiddle with the wallscale convergence factors and get it to converge without resorting to a double precision solver.

April 1, 2010, 10:43	wallscale bulk	#1
mach000 Member Ciro Cannavacciuolo Join Date: Mar 2009 Posts: 35 Rep Power: 17	Hi to everybody, i'm studying a multiphase problem. During the simulation I have some informations about "wallscale bulk". There is someone that could explain me the meaning of this parameters and how I can understand if it's all ok? Thank you very much in advance

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April 2, 2010, 06:10		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	This is the solver working out the distance to walls for the SST turbulence model. As long as it converges a bit it should be fine. It is a very numerically stable solver (and simple mathematics) so rarely causes a problem.

April 2, 2010, 06:46		#3
mach000 Member Ciro Cannavacciuolo Join Date: Mar 2009 Posts: 35 Rep Power: 17	HI, thank you for your reply. The problem is that at the beginning of the simulation I have "Failure" about wallscale bulk and consquently I have overflow. It looks that with double precision simulation the run goes better...

April 2, 2010, 07:02		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	This is quite rare, and yes, sometimes switching to double precision can fix it. Hopefully you are proud to have found such an unusual problem. There are some settings which control it, I have never used them but I know they are there. You might be able to fiddle with the wallscale convergence factors and get it to converge without resorting to a double precision solver.