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 lenson November 7, 2005 01:04

simulate a turbulent flow model

here I simulate a circular pipe. It's type is turbulent. But the outcome tells me that the velociy profile of outlet is almost similar to laminar flow(thin). I try to change the parameters like turbulent intensity (2%、5%、10%)& turburlent length (1/10 inlet length) the outcome is also similar to laminar flow velocity profile. But the velocity profile of turbulent pipe flow is fatter. can anyone help me ? need to change another parameters? or others?

 Tushar November 9, 2005 05:22

Re: simulate a turbulent flow model

ensure that the reynolds number allows the turbulent flow. I think higher turbulence intensity may give you turbulent velocity profile.

Secondly corrected turbulence model has to be selected for the given nature of the problem. Also select MARS Differencing Scheme with BLendinf of 0.5. Try to give Pressure, Outlet as boundary conditions. PUt the convergence criterion of around 1e-05.

 DB November 26, 2005 02:20

Re: simulate a turbulent flow model

Most important is RE>2000.

DB

 lenson December 27, 2005 02:27

Re: simulate a turbulent flow model

here I have a option.firstly,I simulate a turbulent pipe flow which Re=2744.when setting boundary conditions.I gave the inlet flow turbulent intensity=0.1 and length=0.01145(1/10 inlet length).the first one model I putted the turbulent intensity and turbulent length only in inlet boundary condition.Secondly,I not only use all the first model settings but adding the initializaiton(Thermophysical models and properity-->liquids and gases-->initialization).after selecting initialization ,I choose the turbulence panel.here I also give the intensity=0.1 and mixing length=0.01145. are the differences between two cases ?? my guessed answer for first case:that is upward fluid affect downward fluid. the second is all the fluid condition is in turbulence in the beginning when simulating. can anyone help me propose the physical meanings for these two case.

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