# What if I use turbfoam instead of simplefoam what is steady turblence

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 January 18, 2008, 04:13 I noticed in programmers guide #1 Senior Member     Daniel WEI (老魏) Join Date: Mar 2009 Location: Beijing, China Posts: 689 Blog Entries: 9 Rep Power: 13 I noticed in programmers guide, 3.2 Steady turbulent flow over a backward-facing step. So, my questions are 1. What if I use turbfoam instead of simplefoam? 2. How can turbulence be steady? what is steady turbulence? Another two questions are 3. Can I use turbfoam to solve a laminar case, what will it happen? 4. Since Rans like turbFoam.c also contain the d/dt, so concerning the information we get from both RANS and LES, what's the differences between them? Any reply is appreciated. Daniel __________________ ~ Daniel WEI ------------- Boeing Research & Technology - China Beijing, China Email

 January 18, 2008, 08:03 You mean 1. I can use turbFo #3 Senior Member     Daniel WEI (老魏) Join Date: Mar 2009 Location: Beijing, China Posts: 689 Blog Entries: 9 Rep Power: 13 You mean 1. I can use turbFoam, and the answer is the same as using simpleFoam; But simpleFoam is faster and a better choice since it does not have to discretize or solve the temporal item d/dt. 2. backward-facing step flow in programmers guide is a turbulence flow which is statistically steady, and that is what is called steady turbulence. Please correct me if i am wrong. Thank you, Hrv. Daniel __________________ ~ Daniel WEI ------------- Boeing Research & Technology - China Beijing, China Email

 January 18, 2008, 08:09 What about the last two questi #4 Senior Member     Daniel WEI (老魏) Join Date: Mar 2009 Location: Beijing, China Posts: 689 Blog Entries: 9 Rep Power: 13 What about the last two questions? 1. What if I use a solver with RANS method to solve a laminar problem, what will happen? can I get the same result as with the laminar solver? 2. Since Rans solver also contain the discretization of d/dt, and then we get a series of time step result, just like LES method. So concerning the information of result we get from both RANS and LES, what are their differences? I mean concerning the information of the results. Thanks a lot. Daniel __________________ ~ Daniel WEI ------------- Boeing Research & Technology - China Beijing, China Email

 January 18, 2008, 13:13 Ad 1: Nothing. Choose a lamina #5 Senior Member   Hrvoje Jasak Join Date: Mar 2009 Location: London, England Posts: 1,783 Rep Power: 22 Ad 1: Nothing. Choose a laminar "turbulence model" and you're done. Have a look at the equations, ou will see the difference being only the Reynolds stress term. Ad 2: The modelling assumptions are completely different: in RANS you are solving for mean values, whereas in LES you are looking at filtered values - the difference is fundamental. Hrv __________________ Hrvoje Jasak Providing commercial FOAM/OpenFOAM and CFD Consulting: http://wikki.co.uk

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