The Karman-Tsien rule helps explain how the pressure distribution on an airfoil changes as it experiences compressible flow, especially at transonic and supersonic speeds. As an aircraft approaches and surpasses its critical Mach number, compressibility effects become significant. The rule shows that the pressure coefficient Cp decreases with increasing Mach number, primarily due to the acceleration and deceleration of airflow around the airfoil and the formation of shockwaves.
- Pressure coefficient (Cp)
- Incompressible pressure coefficient (Cp,0)
- Freestream Mach number (M∞)
- Specific heat ratio (γ)