Principles of Flight
"A stagnation point of a body in a moving airstream is a point where: (answer) the velocity of the relative airflow is zero and the surface pressure is higher than the ambient atmospheric pressure"
Could you please tell me why surface pressure is higher and not equal to ambient atmospheric pressure? As the book that I read on this says, (perhaps also failing to expand more on this topic),that for incompressible flows, the total pressure of still air is composed of 100% static pressure with 0 % dynamic pressure if there is no movement/velocity involved. As soon as there is velocity given to a body of air, static pressure starts to drop, and total pressure is now also composed of dynamic pressure. The sum of these pressures, P total, is always a constant.
Also, since at the stagnation point where local airflow flow velocity is 0, I take it that static pressure is then highest, meaning no dynamic pressure is present, so shouldn't this pressure then be equal to ambient air pressure of the nearby parcel of air that is unaffected by the wing's passage through it?
I case that I am possibly:
1)using the terms static pressure and stagnation pressure interchangeably, when they actually mean different things, or
2)worrying about a question that was written wrongly to begin with, or
3)not understanding something else that I have failed to mention or learn
How can the surface pressure at the stagnation point be higher than ambient, when the sums of P Static and P Dynamic, in whatever proportions, are always a constant anyway. What is adding that extra pressure?
Appreciate your input