What is true for smooth supersonic compression through weak shocks?

Change in flow velocity is achieved in a shorter distance when closer to the wall than further away

Mach lines formed due to small deflection are divergent

Velocity downstream of the smooth supersonic compression is subsonic

Increase in entropy by a number of weak shocks is greater than the increase by one single shock for a given deflection

Correct Answer : Change in flow velocity is achieved in a shorter distance when closer to the wall than further away

Explanation : Increase in entropy by a number of weak shocks is smaller than a single shock for a given deflection angle. Reduction in entropy is of factor 1/n2, for ‘n’ weak shock waves. Also, the Mach lines are convergent in nature and hence, the change in flow velocity is achieved in a shorter distance when further away from the wall than closer to it. The deflection angle is taken to be small for smooth supersonic compression to obtain supersonic flow downstream.

Recently Updated in Aerodynamics Questions

If there is a supersonic flow over a blunt edge, then the detached shock is observed. Where is the oblique shock observed in the detached shock?

On the blunt edge point

Far away from the edge

Just above the blunt edge point

Near the trailing edge of the section

Correct Answer : Option (C) : Just above the blunt edge point

Explanation : In a detached shock, the normal shock is observed on the blunt edge and then slowly loses strength and becomes an oblique shock just above the edge point. Finally the detached shock becomes a Mach line far away from the edge.

What is true about the flow properties above and below the discontinuity?

The pressure on both sides are different

The pressure on both sides are equal

The flow direction of both sides are different

The density and temperature are the same on both the sides

Correct Answer : Option (B) : The pressure on both sides are equal

Explanation : On either side of the discontinuity the flow direction needs to be same. The pressure is also same on both sides as the flow is not turning.

What is the shape of the pressure curve on the upper surface of a thin diamond wedge airfoil at zero angle of attack?

Pressure increases and becomes constant

Pressure decrease follows a parabolic path

Pressure decreases linearly in a straight line

Pressure increases instantly and becomes constant, and then suddenly becomes negative and becomes constant

Correct Answer : Option (D) : Pressure increases instantly and becomes constant, and then suddenly becomes negative and becomes constant

Explanation : According to shock expansion theory, shock wave interactions determine the aerodynamic loads on the surface of the airfoil. Oblique shock and expansion waves decrease and increase the pressure respectively.