A pitot-static tube placed in the centre of a 300 mm pipe line has one orifice pointing upstream and other perpendicular to it. The mean velocity in the pipe is 0.80 of the central velocity. Find the discharge through the pipe if the pressure difference between the two orifices is 60 mm of water. Take the co-efficient of Pitot tube as Cv = 0.98.

 A pitot-static tube placed in the centre of a 300 mm pipe line has one orifice pointing upstream and other perpendicular to it. The mean velocity in the pipe is 0.80 of the central velocity. Find the discharge through the pipe if the pressure difference between the two orifices is 60 mm of water. Take the co-efficient of Pitot tube as Cv = 0.98. 

Solution. 

Given: 

Dia. of pipe,              d = 30 mm = 0.30 m

Diff. of pressure head, h = 60 mm of water 

                                    = 0.06 m of water 

coefficient of pitot tube,Cv = 0.98 

Mean velocity,             V = 0.80* 

central velocity  Central velocity,V, is given by 

                      =Cv√2gh=0.98*√2*9.81*0.06 

                        V =1.063 m/s 

Mean velocity, V = 0.80 * 1.063 = 0.8504 m/s 

Discharge,                   Q =area of pipe * V 

 =(πd 2 )/4*V 

 =(π*.302 )/4*0.8504 

 = 0.06 m3 /s