Which of these assumptions are not made while obtaining the linearized perturbation velocity potential equation?

Transonic flow is excluded

Subsonic flow is excluded

Hypersonic flow is excluded

Small perturbations are there

Correct Answer : Subsonic flow is excluded

Explanation : In order to obtain the linearized perturbation velocity potential equation, there are few assumptions made. The perturbations u‘, v‘, w‘ are assumed to be small in comparison to the free stream velocity. Apart from this the equation is not applicable for transonic flow with Mach number between 0.8 and 1.2 and for hypersonic flow with Mach number greater than 5.

Recently Updated in Aerodynamics Questions

Under which condition do we get the detached shock wave on a cone?

θ_c = 0

θ_c = infinty

θ_c = θ_cmax

θ_c > θ_cmax

Correct Answer : Option (D) : θ_c > θ_cmax

Explaination : For a given freestream Mach number M_∞, there exists a maximum cone angle for which if we go beyond that value, the shock wave originating at the cone’s vertex gets detached. Thus, the condition for detached shock wave is θ_c > θ_cmax.

What is the relation between maximum allowed cone angle and wedge angle for attached shock wave?

(θ_max)_wedge = (θ_max)_cone

(θ_max)_wedge > (θ_max)_cone

(θ_max)_wedge < (θ_max)_cone

(θ_max)_wedge ≈ (θ_max)_cone

Correct Answer : Option (B) : (θ_max)_wedge > (θ_max)_cone

Explaination : Due to the three-dimensional relieving effect, for a particular freestream Mach number, the maximum cone angle allowed is larger than the maximum wedge angle before the shock wave becomes detached.

Where does the flow remain supersonic in a conical surface?

Between the oblique shock and the sonic line

Between the sonic line and the conical surface

Flow is not supersonic beyond the oblique shock

Between the oblique shock and the conical surface

Correct Answer : Option (A) : Between the oblique shock and the sonic line

Explanation : The incoming flow over a cone is mostly supersonic between the surface of the cone and the oblique shock wave. Except in some cases when the half cone angle is large, flow sometimes becomes subsonic and one of the rays originating the cone’s vertex acts at the sonic line. The flow between the sonic line and the oblique shock thus remains supersonic.