Talk:Turbulence modeling
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(low-re models and heat trasfer coefficients) |
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| + | 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?
Thanks in advance.
Massimo
