i have took a basic course in fluid mechanics: Bernoulli equation states that: P + (1/2)*ρ*v^2 + ρ*g*h = constant where P is the pressure , ρ is the density , g is the garvitational acceleration and h is the distance from the center of the earth , and that constant is our reference. that means if thier was a tube carrying a stream of fluid with velocity V , the pressure on the wall of the tube would be: (1/2)*ρ*v^2 + ρ*g*h + constant what does that mean in a microscopic scale ? what happen with the interaction of the molecules of the wall and the fluid ? and can their exist pressure inside the fluid due to the viscosity of the fluid ? if we assume that every layer moves with a speed different that the next layer due to viscosity? and if so , how would the pressure affect the stream ?