Two of the assumptions in Brenoulli's Theorem say 1. The fluid should be non-viscous 2. The velocity of fluid should be less than its critical velocity Now how can these two co-exist. We know that Vc = (N.n)/(D.p) Vc= Critical Velocity N= Raynolds No. n= viscosity coef. D= Dia of pipe p= dencitu of fluid if n=0 the Vc=0 i.e. fluid is static. If there is no flow then what are we studying here. Please explain anybody.