CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   FLUENT (http://www.cfd-online.com/Forums/fluent/)
-   -   Macro to set Wall Shear Stress (http://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
 
I think U can use Lookup_Thread and get the thread.

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 ?


All times are GMT -4. The time now is 09:56.