What is the reason for a sudden increase in drag beyond drag divergence?

The shape of the airfoil

Prandt- Glauert compressibility effect

Transonic region on top surface of the airfoil

Supersonic region on top and bottom region of the airfoil

Correct Answer : Supersonic region on top and bottom region of the airfoil

Explanation : When the Mach number is increased beyond the point of drag divergence, the drag decreases by a factor of 10 due to the formation of supersonic region in both top and bottom surfaces of the airfoil. This supersonic region is followed by a shock wave which leads to flow separation causing higher drag.

Recently Updated in Aerodynamics Questions

What happens to the coefficient of pressure in a supersonic flow for an increase in Mach number?

Increases

Decreases

Remains unaffected

First increases then decreases

Correct Answer : Option (B) : Decreases

Explanation : For linearized supersonic flow, the coefficient of pressure is inversely proportional to

Thus, when the Mach number increases, the coefficient of pressure decreases. This in contrast to the trend followed by the subsonic flow where an increasing Mach number results in decreasing coefficient of pressure.

What is the source of wave drag exerted on the supersonic airfoil?

Skin friction

Trailing vortex

Shock waves

Viscous boundary layer

Correct Answer : Option (C) : Shock waves

Explanation : Wave drag is a result of pressure distribution which is exerted over the airfoil. This is a consequence of formation of shock waves and expansion wave pattern due to the presence of supersonic flow.

What is the lift coefficient over a flat plate at an angle of attack of 3 degrees in a supersonic flow at Mach 4?

0.0512

0.0541

0.0628

0.0714

Correct Answer : Option (B) : 0.0541

Explanation :