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-   -   Macro to set Wall Shear Stress (https://www.cfd-online.com/Forums/fluent/32526-macro-set-wall-shear-stress.html)

 Satish November 15, 2003 18:00

Macro to set Wall Shear Stress

hi

can anyone help me in writing a udf to set the wall shear stress as below

Wall Shear Stress = (5/16)*(density*sqrt(2*pi*R*T))*((3/4)*(viscosity/density*temp)*dt/dxw)

Heat Flux = sqrt(2*pi*R*T)*C*(5*density*Cp/16)*(Tw - Tg)

here i need to write this in DEFINE_ADJUST as i need to update the value for every iteration. I know the macros for all the terms in the above eqn. except the wall shear stress and heat flux. Can any one help me in this

dt/dxw = derivative of temperature wrt x at the wall

Thanks

Satish

 Ajay Rao November 16, 2003 17:34

Re: Macro to set Wall Shear Stress

But with DEFINE_ADJUST how would you get the thread of of wall ? So that you could loop over it. If you find something let me know , i need it in my calculations ! Thanks , Ajay

 Satish November 16, 2003 17:47

Re: Macro to set Wall Shear Stress

Do u know the macro for Wall Shear Stress ?

Thanks Satish

 Ajay Rao November 16, 2003 19:33

Re: Macro to set Wall Shear Stress

Oh yeah Right , I forgot about the Lookup_Thread ! I tried calculating the derivatives for shear stress on the wall by finding the derivatives at the cell centroid C_DUDX rather than the face. My drag force is completly wrong ! Still working on it . WIll post it if i come up with something.

Thanks, Ajay

 co2 November 26, 2003 15:46

Re: Macro to set Wall Shear Stress

so ajay, did you come up with something ?

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