Contents
What is a transonic airfoil?
Transonic (or transsonic) flow is air flowing around an object at a speed that generates regions of both subsonic and supersonic airflow around that object. Research has been done into weakening shock waves in transonic flight through the use of anti-shock bodies and supercritical airfoils.
What causes wave drag over an airfoil in transonic flow?
Wave drag is caused by the formation of shock waves around the aircraft in supersonic flight or around some surfaces of the aircraft whilst in transonic flight. Shock waves radiate a considerable amount of energy, resulting in drag on the aircraft.
What is the family of airfoils specifically designed for transonic flight?
A supercritical airfoil (supercritical aerofoil in British English) is an airfoil designed primarily to delay the onset of wave drag in the transonic speed range.
Why do shock waves increase drag?
When an aircraft approaches the speed of sound, the airflow over the wing reaches supersonic speed before the airplane itself does, and a shock wave forms on the wing. The airflow behind the shock wave breaks up into a turbulent wake, increasing drag.
Is wave drag induced or parasite?
Parasitic drag is a combination of form drag and skin friction drag. It affects all objects regardless of whether they are capable of generating lift. The other components of total drag on an aircraft, such as lift–induced drag and wave drag, are separate types of drag, and are not components of parasitic drag.
Do bullets go supersonic?
Bullets are normally traveling their fastest as they leave the barrel of the gun, so the sonic boom is generally covered by the firearm going bang.
How does a shock control bump affect the transonic buffet?
Current research shows that the traditional shock control bump (SCB) can weaken the intensity of shock and better the transonic buffet performance. The author finds that when SCB is placed downstream of the shock, it can decrease the adverse pressure gradient.
What happens to the shocks of an airfoil as the Mach number increases?
As the Mach number approaches one, the shocks move all the way to the trailing edge. Finally, when the Mach number becomes slightly greater than one, a bow wave appears just ahead of the airfoil, and the shocks at the trailing edge become oblique.
Why do shock waves increase as the speed increases?
As the Mach number increases, shock waves appear in the flowfield, getting stronger as the speed increases. The shock waves lead to a rapid increase in drag, both due to the emergence of wave drag, and also because the pressure rise through a shock wave thickens the boundary layer, leading to increased viscous drag.