A new mass-weighted(MAW)upwind interpolation scheme

the control-volume finite-element method

is adopted for three dimensional convection term based on tetrahedral element

and its subcontrol volumes and surfaces on each element are symmetrical.This feature not only guarantees the positive coefficients in the discretization equation

but also is easy to be fulfilled in the computer program.The scheme has been applied successfully to some three dimensional convection-diffusion problems and some three dimensional viscous

incompressible fluid flow problems.