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laminar/turbulent viscosity at the wall interface

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Old   March 9, 2006, 02:07
Default laminar/turbulent viscosity at the wall interface
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kcng
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Hi:

Appreciate if you could clear my confusion, as follows:-?

In a typical flow region, the values of laminar and turbulent viscosities at the cell faces in a cell-centered solver can be easily determined from linear interpolation between the two interconnected cells, which serve as a contribution of the diffusive fluxes for any interior cells.

For cells adjacent to the wall, in order to evaluate the diffusive fluxes for those cells, I presume that we must have the laminar/turbulent viscosity at the wall (interface for the wall-adjacent cell) as well?? What will be the values then??

Pls reply fast. Thank you very much.

kcng

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Old   March 9, 2006, 05:34
Default Re: laminar/turbulent viscosity at the wall interf
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versi
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onlu laminar viscosity on the wall interface.
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Old   March 9, 2006, 06:09
Default Re: laminar/turbulent viscosity at the wall interf
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kcng
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Dear Versi, Thanks for the fast reply..

I presume that your answer is based on the fact that eddy/turbulent viscosity is the property of flow, rather than fluid? If that so, eddy viscosity at exactly the wall interface is zero (zero fluctuation)? In certain cases, where we are used to impose Newmann condition for k (such as Low -Re Turbulence Model), what will be the proper procedure to set the turbulent viscosity at the wall interface then?

Rgd the determination of diffusive fluxes (in the framework of FVM) of standard k-e model at the wall interface, does that mean I have to consider the contribution of (Miu_laminar*dk/dn @ wall) as well, apart from imposing the wall-function for std k-e model by calculating the generation of turbulent kinetic energy per unit volume (Veersteeg and Malalasekara, 1996)at cells adjacent to the wall? In fact, how they come out with the generation of term 'turbulent kinetic energy per unit volume'? Can anyone pls enlighten?

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Old   March 10, 2006, 06:42
Default Re: laminar/turbulent viscosity at the wall interf
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John Luo
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At the wall, turbulent viscoisty is always zero because k is zero (dissipation rate is not zero). If you are using low Reynolds number models, then the shear stress at wall is dominated by laminar viscosity, and at the wall, only laminar shear stress needs to be calculated (in genernal the turbulent viscoisty in the near wall cell centre should be much smaller than the laminar viscosity in the low Re model).

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