Hello,
I'm simulating an airfoil at an AoA of 60°, i understand that in the lower surface must be a high Pressure Coefficient due to the Stagnation pressure, but i really don't understand why the negative pressure in the upper surface, i mean the velocity is near 0 due to the separation of boundary layer, so it should't produce a negative pressure.
I would really appreciate if you help me to understand this behavior.
Thanks!
The pressure value is expressed with respect to the reference pressure. So, the negative value is just an indication of a pressure value less than the reference vale.
The drop of pressure in the upper side is due to the separation of fluid, which doesnt allow the pressure recuperation in this region.
Dear José, pressure coefficient Cp = (p - pinf)/(1/2 rho Vinf2) is related to the pressure difference from pinf = flow pressure at infinity; at upper (rear) surface, flow must cover the "wake" due to high speed flow streamlines at upper at below points of airfoil (red domains in fig.2), so flow moves from left to right (of your pictures); so on surface p < pinf, therefore Cp < 0. Gianluca
You need to scale the value considering the pressure reference! As you can see in the label, you have O(10^2) Pa while standard value at sea level is O(10^5) Pa (or N/m^2).
- Badges
- Science topic