# Talk:Turbulence modeling

(Difference between revisions)
 Revision as of 05:31, 13 September 2005 (view source)Zxaar (Talk | contribs)← Older edit Revision as of 16:06, 20 December 2005 (view source) (low-re models and heat trasfer coefficients)Newer edit → Line 1: Line 1: + Hi + I'm working on oil distribution analysis. My flow model consists on small passages (diam. 4 mm) + and I have to run a steady-state analysis with a commercial Code. Re number is about 12000. Flow enters + from a circular tube (Inlet b.cond.) and exit from two ducts (Pressure b. cond) + 1) I cannot use k-eps high-Re with wall function because I should use a 0.8-1 mm cell at wall + in order to have correct y+ (30-100). + 2) Then I tried to use both two layer models and k-eps low-Re/Hybrid Wall Function with a proper fine + mesh at wall (15 layers with y+ less than  1). + I do not know if the second way is correct or not. I can only say that by using the last two turbulence models + 3) I found some strange values for heat transfer coefficients at wall, about 24000-30000 W/m2 K while proper + values should be 4000-5000 W/m2 K + Could anyone tell me why I found so high heat trasfer coefficients and if low-Re models are correct or not + for such calculations? + + Thanks in advance. + + Massimo

## Revision as of 16:06, 20 December 2005

Hi I'm working on oil distribution analysis. My flow model consists on small passages (diam. 4 mm) and I have to run a steady-state analysis with a commercial Code. Re number is about 12000. Flow enters from a circular tube (Inlet b.cond.) and exit from two ducts (Pressure b. cond) 1) I cannot use k-eps high-Re with wall function because I should use a 0.8-1 mm cell at wall in order to have correct y+ (30-100). 2) Then I tried to use both two layer models and k-eps low-Re/Hybrid Wall Function with a proper fine mesh at wall (15 layers with y+ less than 1). I do not know if the second way is correct or not. I can only say that by using the last two turbulence models 3) I found some strange values for heat transfer coefficients at wall, about 24000-30000 W/m2 K while proper values should be 4000-5000 W/m2 K

Could anyone tell me why I found so high heat trasfer coefficients and if low-Re models are correct or not for such calculations?