# Macro to set Wall Shear Stress

 Register Blogs Members List Search Today's Posts Mark Forums Read

 November 15, 2003, 17:00 Macro to set Wall Shear Stress #1 Satish Guest   Posts: n/a 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

 November 16, 2003, 16:34 Re: Macro to set Wall Shear Stress #2 Ajay Rao Guest   Posts: n/a 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

 November 16, 2003, 16:47 Re: Macro to set Wall Shear Stress #3 Satish Guest   Posts: n/a I think U can use Lookup_Thread and get the thread. Do u know the macro for Wall Shear Stress ? Thanks Satish

 November 16, 2003, 18:33 Re: Macro to set Wall Shear Stress #4 Ajay Rao Guest   Posts: n/a 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

 November 26, 2003, 14:46 Re: Macro to set Wall Shear Stress #5 co2 Guest   Posts: n/a so ajay, did you come up with something ?