Pitot Tube

Pitot tube is a measurement device used to measure fluid flow velocity. The pitot tube was invented by the French engineer Henri Pitot in the early 18th century and was modified to its modern form in the mid-19th century by French scientist Henry Darcy. It is widely used to determine the airspeed of an aircraft, water speed of a boat, and to measure liquid, air and gas flow velocities in certain industrial applications. It is based on the principle that if the velocity of flow at a point becomes zero, the pressure there is increased due to the conversion of the kinetic energy into pressure energy. In its simplest form, the pitot-tube consists of a glass tube, bent at right angles. The lower end, which is bent through 90° is directed in the upstream direction. The liquid rises up in the tube due to the conversion of kinetic energy into pressure energy. The velocity is determined by measuring the rise of liquid in the tube.
Consider two points (1) and (2) at the same level in such a way that point (2) is just as the inlet of the pitot-tube and point (1) is far away from the tube.
Let,   p1 = intensity of pressure at point (1)
          v1 = velocity of flow at (1)
          p2 = pressure at point (2)
          v2 = velocity at point (2), which is zero
          H = depth of tube in the liquid
          h = rise of liquid in the tube above the free surface.
Apply Bernoulli's equation at points (1) and (2), we get

            

 Credit:- https://en.m.wikipedia.org/wiki/Pitot_tube

Book Author- DR.R.K.Bansal