GATE AE Potential Flow: Previous Year Questions

GATE AE 2026, Question 15 (1 mark, MCQ)

Aerodynamics - Potential Flow

In fluid dynamics, d'Alembert's paradox refers to which one of the following?

1. Deviation of drag from $D \propto v^2$ at very low speeds
2. Deviation of drag from $D \propto v^2$ at high subsonic speeds
3. Prediction of zero drag by potential flow theory
4. Presence of shocks in transonic flows

Official answer: C

GATE AE 2026, Question 19 (1 mark, MCQ)

Aerodynamics - Potential Flow

The velocity potential function ($\varphi$) given below represents which one of the following? $$\varphi = 5x - 12y$$

1. Doublet
2. Irrotational vortex
3. Source
4. Uniform flow

Official answer: D

GATE AE 2026, Question 47 (2 marks, MSQ)

Aerodynamics - Potential Flow

Consider the flow over an oval modeled using the elementary potential flows as shown below. $U$ represents uniform flow velocity and $\Gamma$ represents circulation around an irrotational line vortex. Which of the following statements is/are TRUE for this model?

1. Increasing $U$ enlarges the oval
2. Increasing $\Gamma$ enlarges the oval
3. Interchanging the sense of the two vortices does not alter the oval
4. Moving the vortices too far apart causes the oval to break up

Official answer: B, D

GATE AE 2025, Question 20 (1 mark, MCQ)

Aerodynamics - Potential Flow

Consider a pair of point vortices with clockwise circulation $\Gamma$ each. The distance between their centers is $a$, as shown in the figure. Assume two-dimensional, incompressible, inviscid flow. Which one of the following options is correct?

1. The vortices translate downwards together with a velocity $\dfrac{\Gamma}{2\pi a}$.
2. The vortices translate upwards together with a velocity $\dfrac{\Gamma}{2\pi a}$.
3. The vortices rotate clockwise around each other about their centroid O.
4. The vortices rotate counter-clockwise around each other about their centroid O.

Official answer: C

GATE AE 2025, Question 34 (1 mark, NAT)

Aerodynamics - Potential Flow

The lift per unit span for a spinning circular cylinder in a potential flow is 6 N/m. The free-stream velocity is 30 m/s, and the density of air is 1.225 kg/m$^3$. The circulation around the cylinder is ____ m$^2$/s (rounded off to two decimal places).

Official answer: 0.16 to 0.17

GATE AE 2024, Question 21 (1 mark, MCQ)

Aerodynamics - Potential Flow

In the context of steady, inviscid, incompressible flows, consider the superposition of a uniform flow with speed $U$ along the positive $x$-axis (from left to right), and a source of strength $\Lambda$ located at the origin. Which one of the following statements is **NOT** true regarding the location of the stagnation point of the resulting flow?

1. It is located to the left of the origin
2. It moves closer to the origin for increasing $\Lambda$, while $U$ is held constant
3. It moves closer to the origin for increasing $U$, while $\Lambda$ is held constant
4. It is located along the $x$-axis

Official answer: B

GATE AE 2023, Question 16 (1 mark, MCQ)

Aerodynamics - Potential Flow

In a two-dimensional potential flow, the doublet is a limit of the superposition of

1. a uniform stream and a source
2. a source and a sink of equal strength
3. a uniform stream and a sink
4. a source and a vortex

Official answer: B

GATE AE 2023, Question 57 (2 marks, NAT)

Aerodynamics - Potential Flow

In a potential flow, a uniform stream of strength $U$ directed along the $x$-axis and four line sources (2-dimensional) of strengths $\dfrac{\pi}{2}, \dfrac{-\pi}{3}, \dfrac{\pi}{4}, \dfrac{-\pi}{5}$ are placed along the $x$-axis at $x = 0, 1, 2$ and $3$, respectively. The strength of an additional line source to be placed at $x = 4$ such that a closed streamline encircles all five sources is _____. (round off to two decimal places).

Official answer: -0.69 to -0.67

GATE AE 2022, Question 15 (1 mark, MCQ)

Aerodynamics - Potential Flow

Consider a two-dimensional potential flow over a cylinder. If the freestream speed is $U_\infty$, the maximum speed on the cylinder surface is

1. $\dfrac{U_\infty}{2}$
2. $\dfrac{3U_\infty}{2}$
3. $2U_\infty$
4. $\dfrac{4U_\infty}{3}$

Official answer: C

GATE AE 2018, Question 23 (1 mark, MCQ)

Aerodynamics - Potential Flow

In a low-speed wind tunnel, the angular location(s) from the front stagnation point on a circular cylinder where the static pressure equals the free-stream static pressure, is

1. $\pm 38^\circ$
2. $\pm 30^\circ$
3. $\pm 60^\circ$
4. $0^\circ$

Official answer: B

GATE AE 2016, Question 12 (1 mark, NAT)

Aerodynamics - Potential Flow

Due to a body in potential flow, the velocity at a point A in the flow field is 20 m/s while the free stream velocity is only 10 m/s. The value of coefficient of pressure ($C_p$) at the point A is _________.

Official answer: -3

GATE AE 2016, Question 39 (2 marks, MCQ)

Aerodynamics - Potential Flow

The maximum value of coefficient of lift ($C_l$) for a 2D circular cylinder, provided at least one stagnation point lies on the cylinder surface, is predicted by the potential flow theory to be

1. $\pi/2$
2. $\pi$
3. $2\pi$
4. $4\pi$

Official answer: D

GATE AE 2014, Question 19 (1 mark, MCQ)

Aerodynamics - Potential Flow

The streamlines of a potential line vortex is concentric circles with respect to the vortex center as shown in figure. Velocity along these streamlines, outside the core of the vortex can be written as, $v_\theta = \dfrac{\Gamma}{2\pi r}$, where strength of the vortex is $\dfrac{\Gamma}{2\pi}$ and $r$ is radial direction. The value of circulation along the curve shown in the figure is:

1. $\Gamma$
2. $-2\Gamma$
3. $2\Gamma$
4. 0

Official answer: D