TWO-PHASE FLUID FLOW Fluid Flow where: DP   = Pressure spike lbf ft² r    = Density of the fluid lbm ft³ c     = Velocity of the pressure wave ft sec (Speed of sound in the fluid) Dv   = Change in velocity of the fluid ft sec g_c = Gravitational constant  32.17 lbm  ft lbf  sec² Example:    Pressure spike Water at a density of 62.4 lbm/ft³ and a pressure of 120 psi is flowing through a pipe at 10 ft/sec.  The speed of sound in the water is 4780 ft/sec.  A check valve suddenly closed.   What is the maximum pressure of the fluid in psi? Solution: P_Max = P_Static + DP_Spike P_Max =  120^lbf in² rc  DV g_c P_Max =  120^lbf in² 62.4^lbm ft³ 4780^ft sec 10^ft sec 32.17 lbm  ft lbf  sec² P_Max =  120^lbf in² 92,631^lbf ft² ft² 144  in² P_Max =  120^lbf in² 643.3^lbf in² P_Max = 763.3 psi HT-03 Page 44 Rev. 0