Abstract: As a robust and efficient numerical method, the upwind flux differencesplitting method has been used to simulate complex viscous flow However, when the simulated supersonic viscous flow contains shear or boundary layers, the flux difference split must be conservative. If not, either an abnormally large numerical diffusion occurs within the boundary layer, or a fictitious pressure gradient is created that causes an unrealistic convection within the layer and misrepresents the boundary layer character. For th...