CFD Online Discussion Forums

Hello,

I would like to have $u^{+}$ contours.

$u^{+} = \frac{u}{u_\tau}$ and $u_{\tau} = \sqrt{\frac{\mid \tau_w \mid}{\rho}}$

So, I create the variable uplus like this:

HTML Code:

// Wall Shear Stress

wss = sqrt ( Wall Shear X * Wall Shear X + Wall Shear Y * Wall Shear Y + Wall Shear Z * Wall Shear Z )



uplus = Velocity / sqrt ( wss / rho)

I plot it and am happy.

But then I realized it should be 0, because Velocity is 0 at the wall.
So I tried something:

1- If I plot the velocity at a wall 'directly', I have 0 everywhere, it's ok (face values)
2- If I create a variable equal to the Velocity and plot it at the wall, I don't have 0.

So I think that when you create a variable, it's for cell centres, right? It would be nice since it directly take the first cell from the wall to calculate $u^{+}$