# Aerodynamics Questions and Answers – Source Flow

This set of Aerodynamics Questions and Answers for Campus interviews focuses on “Source Flow”.

1. The flow in which streamlines are directed away from the origin is called as __________
a) sink flow
b) doublet flow
c) source flow
d) source-sink flow

Explanation: In a source flow, the flow velocity is directed away from the origin. All the streamlines are the straight lines and they vary inversely with distance which means as the distance increases the velocity decreases.

2. The opposite case of the source flow is ___________
a) sink flow
b) doublet flow
c) source flow
d) source-sink flow

Explanation: The flow in which the streamlines are directed towards the origin is called as sink flow. The sink flow is simply the negative of source flow. The streamlines vary inversely with the distance that is as the distance decreases the velocity increases.

3. The origin is called as _________
a) singular point
b) multiple point
c) sink point
d) source point

Explanation: For a source flow, divergence of velocity is zero everywhere expect at the origin where it is infinite. Thus, the origin is a singular point and we can interpret this singular point as a discrete source or sink of a given strength, with a corresponding induced flow field about the point.

4. In the source flow, the tangential velocity component is _________
a) 0
b) 1
c) not defined
d) infinity

Explanation: In the source flow, the velocity component is only in the radial direction (Vr). The tangential component of the velocity (Vt) is zero.

5. ___________ is the scalar function of the space and time.
a) velocity
b) velocity potential function
c) velocity vector
d) pressure

Explanation: Velocity function is the scalar function of space and time such that its negative derivative with respect to any direction gives the fluid velocity in that direction. It is defined by phi (ϕ). Mathematically, it is given by, ϕ= f(x,y,z).

6. For a steady flow, the velocity potential function for velocity V can be given by _______
a) u = -δϕ/δx, v = δϕ/δy, w = δϕ/δx
b) u = δϕ/δx, v = δϕ/δy, w = δϕ/δx
c) u = -δϕ/δx, v = -δϕ/δy, w = δϕ/δ
d) u = -δϕ/δx, v = -δϕ/δy, w = -δϕ/δx

Explanation: Velocity potential function is scalar function of space and time and its negative derivative with respect to any direction gives the fluid velocity in that direction. Mathematically, it is ϕ = f(x,y,z) such that,
u = -ϕδ/xδ,
v = -ϕδ/δy,
w = -ϕδ/δx.

7. Stream function is defined for ____________
a) 2D flow
b) 3D flow
c) 1D flow
d) multi-dimensional flow

Explanation: Stream function are applicable only for 2D flow. It is denoted by psi (Ψ). For a steady state flow, it is given by- Ψ=f(x,y), such that
δΨ/δx=v and δΨ/δy=u.

8. ______ gives the velocity component at right angles to a particular direction.
a) velocity
b) velocity vector
c) stream function
d) pressure line

Explanation: Stream function is defined as the scalar function of space and time such that its partial derivative with respect to any direction gives the velocity component at right angles to that direction. It is valid only for 2D flow and is denoted by Ψ.

9. When velocity potential (ϕ) exits, the flow is _________
a) rotational
b) irrotational
c) laminar
d) turbulent

Explanation: When the rotational components are zero, it means that the flow travels in a linear direction and the velocity potential gives the direction of fluid velocity in a particular direction. In irrotational flow, the velocity of the fluid travels in a linear direction.

10. For an irrotational flow, the velocity component along z-direction becomes _________
a) 0
b) 1
c) infinity
d) -1

Explanation: In irrotational flow, the fluid flows in linear direction only and if the stream function exits the flow may be either rotational or irrotational. When the stream function satisfies the Laplace equation, it the case of irrotational flow.

Sanfoundry Global Education & Learning Series – Aerodynamics.

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