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Old   January 25, 2008, 04:43
Default Wall boundary condition – UDF
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Dear All,

I have gas-solid flow in 2D domain and would like to specify a wall boundary condition for solid phase. Radial velocity of particles should be zero at wall and for axial velocity there is a correlation;


Up=(dp/Ep**0.333)*d(Up)/dr @ r=R

dp=solid diameter

Ep=solid holdup

d(Up)/dr= partial derivation with respect to r


I know that I should do it by UDF - coupled at specified shear panel. Parameters will be;

Visco = C_Mu(cell,thread_g)

y_vel_s = C_V (cell,thread_s) ->tangential velocity-to-wall

diam = C_Phase_Diameter (cell, thread_s)

void_g = C_VOF (cell, thread_g)


Shear = -Mu*dV/dr

Shear stress y component; Shear_y = Visco*pow((1-void_g),(1/3))/diam*y_vel_s

I don't know how to define shear stress x component? And also I am not sure if I can use the above shear definition at wall?

Does anyone have an experience with this type of bc and UDF??



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