Hi, all

I have used the convective BC for outflow condition in my code. However, I am not quite understand that how to set the outflow condition for a variable shear to the outlet.

For instance, for an backstep test, the fluid flow from the left to right, and I set this direction as U(which is normal to the outlet), clearly, the U at outlet can be solved with CBC condition equation,

Un[i] = U[i] - c*(U[i]-U[i-1])*dt/dx , c is some const speed

My question is that how to solve the V and W at the outlet? Use the same way or just set them to zero?

I have also heard that if the Peclet Number is huge, then we need no BC for the outflow, is it right?

regards, shengyong

hi pang,

You must use the same procedure for v and w. Just replace v,w...inplace of u.

thanks.