impact pressure

i. The pressure of a moving fluid brought to rest that is in excess of the pressure the fluid has when it does not flow (i.e., total pressure less static pressure). Impact pressure is equal to dynamic pressure in an incompressible flow, but, in a compressible flow, impact pressure includes the pressure change attributable to the compressibility effect.

ii. A measured quantity obtained by placing an open-ended tube, known as an impact tube or a pitot tube, in a gas stream and noting the pressure in the tube on a suitable manometer. Since the pressure is exerted at a stagnation point, the impact pressure is sometimes referred to as the stagnation pressure or the total pressure. See stagnation pressure.