6.1 Source terms in momentum equations and two key issues in numerically solving momentum equation 6.1.1 Introduction 6.1.2 Source in momentum equations 6.1.3 Two key issues in solving flow field 6.2 Staggered grid system and discretization of momentum equation 6.2.1 Staggered grid(交叉网格) 6.2.2 Discretization of momentum equation in staggered grid 6.2.3 Interpolation in staggered grid 6.2.4 Remarks 1. Flow rate at a node 2. Density at interface 3. Conductance at interface 6.3 Pressure correction methods for N-S equation 6.3.1 Basic idea of pressure correction methods 6.3.2 Equations for velocity corrections of u ’, v ’ 6.3.3 Derivation of equation of pressure correction p ’ 6.3.4 Boundary condition for pressure correction