4.2 The acceleration Field of a fluid V(r,t=iu(x, y,z, t)+jv(x,y, z, t)+hw(,y,z, t) C a dt +k dt at Ox ot oy at az at ou l一+1一+ Nonlinear terms Local acceleration Convective acceleration a ≠0 unsteady ≠0 nonuniform dt3 4.2 The Acceleration Field of a Fluid V r t iu x y z t jv x y z t kw x y z t ( , ) ( , , , ) ( , , , ) ( , , , ) = + + dV du dv dw a i j k dt dt dt dt = = + + du u u x u y u z dt t x t y t z t        = + + +        u u u u u v w t x y z     = + + +     Local acceleration unsteady 0 t    Convective acceleration nonuniform 0 i x    Nonlinear terms