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-   -   B.C. for turbulent mixing layers (http://www.cfd-online.com/Forums/main/1978-b-c-turbulent-mixing-layers.html)

 Jason March 29, 2000 16:06

B.C. for turbulent mixing layers

Hello everyone,

I am now working on the numerical modelling of plane mixing layers using SIMPLE code, my computation domain is of a rectangular shape, for inlet, experimental data is used, and the Neumann condition is applied for outlet, how can I give the B.C. for the other two entrainment boundries(the boundry which parallel the main flow direction)? thanks.

 John C. Chien March 29, 2000 16:55

Re: B.C. for turbulent mixing layers

(1).In the two stream mixing case, you can specify the outer boundaries as free stream boundaries. That is the same as the inlet boundary conditions away from the mixing plane. (2). I don't use the code you mentioned, so you need to check the code the available boundary conditions. Normally, there will be inlet, outlet, wall, far-field boundary conditions. (2). A moving wall at the inlet velocity is also all right to use. But remember to check the effect on the flow field after the solution is obtained. In principle, the boundary conditions should be placed far away from the area of interest. So, it is important to move the outer boundary away from the mixing plane to check the effect.

 C.U.D May 12, 2000 13:34

Re: B.C. for turbulent mixing layers

(1)Inflow B.C :Velocity "U" used 'Tanh' profile (fixed)

Velocity "v" used 'Random perturbation'(eigenfunction)& superimposed to the mean flow

Density "D" Obtained from D*U=CONST

Pressure "p" used"Upwind"or called "One side

differenced" Given value on "Guard

cell"(Because downstream effects)

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