Tube Flow 0-） 点4 密 in a tube:flow -” g-49mn0 The parallel-plate plastometer (or squeeze-film)geometry F.v The rate of change of the separation h with respect to timet is dh2 dt3xn For a given volume with an initial radiusr and height h,then if it stays within the plates, F=3发 1010 Newtonian Fluids γ Ý w = 4Q πa3 σ w = Pa 2L η = σ γ Ý = Pπa4 8LQ γ Ýw and σ w are values or shear rate and stress at the wall of the tube. At the center of the tube : γ Ý oand σ o = 0 Tube Flow u r( )= P 4ηL a2 − r2 ( ) F,v The rate of change of the separation h with respect to time t is dh dt = 2Fh3 3πηa4 For a given volume with an initial radius ro and height ho, then if it stays within the plates, F = 3πηvro 4 ho 2 h5 The parallel-plate plastometer (or squeeze-film) geometry