Help. implicit discritization
 

Hi everybody,

I have written a 3D code for flow around circular cylinder. I have used implicit three-layer backward (Euler method) method for time discretization. for convection terms the upwind and for viscous terms the central scheme has been used.
I have discretized viscous terms as implicit and I retained convection terms as explicit. only 7 finite volumes are retained in the implicit discrete operator( (i,j,k),(i+1,j,k),(i-1,j,k),(i,j+1,k),(i,j-1,k),(i,j,k+1),(i,j,k-1) ). The discretized equations are solved with point by point Gauss-Seidel method.

Question:

1) Is it,retaining the convection terms as explicit, true ? due to using upwind method the implicit discretization of convection terms is difficult(for me).what is your suggestion to me?

Thanks,