Please can someone help out with the actual concept of stagnation,static and dynamic pressures . I have learnt all that stagnation pressure is when velocity of flow is 0 when isentropically stopped and dynamic pressure is the product of 0.5 times density and velocity squared and static as actuall pressure. But I am still not able to comprehend the physical significance of it.
The total (stagnation) pressure is the summation of the static and dynamic pressures for incompressible flow (see Bernoulli equation). The dynamic pressure is a measure of the fluid's kinetic energy (https://www.engineeringtoolbox.com/dynamic-pressure-d_1037.html). The faster a fluid travels, the more kinetic energy and dynamic pressure it has. This website has a good description and diagrams of the concept (http://kb.eng-software.com/eskb/pipe-flo/general-theory-and-equations/total-and-static-pressure). A more physical interpretation of this concept is flow in a convergent duct. For isentropic subsonic conditions, the flow velocity increases as the area decreases. Therefore, the dynamic pressure increases and the static pressure decreases. The opposite can be said for isentropic subsonic flow in a divergent duct; the velocity decreases as the flow area increases. Thus, the dynamic pressure falls in a divergent duct with subsonic flow. For further reading on the concept of total, static, and dynamic conditions, look into the operating principle behind Pitot tubes. I hope this was helpful.