Rotational nosy unimpressible ideal-fluid 、 Translating motion Velocity of each point concludes ux,u,, known from figure 6-1, ux, uy is translating velocity 2、 Deformation motion (1) Linear deformation Taking AB as example. due to velocity of angle point B is Ou faster than angle point A along direction x(or slower) Ox u so through dt, protraction of side AB along x(or condense)isa- dx- dt x Linear deformation of unit length in unit time called linear deformation velocity, and written, E, i=x,y, z)then dx·d/(dx.at ou similarly E,m,= (6-1) Oy11 Velocity of each point concludes ,known from figure 6—1, is translating velocity. ux uy , ux uy , （1）Linear deformation Taking AB as example.Due to velocity of angle point B is faster than angle point A along direction x (or slower) , so through , protraction of side AB along x (or condense)is .Linear deformation of unit length in unit time called linear deformation velocity ,and written， then dx x ux         dt dx dt x ux          (i x y z) ij  = , , 1、Translating motion 2、Deformation motion ( ) x u dx dt dx dt x ux x xx     =    = y uy yy    = z uz zz    =  similarly （6—1）