# Aerodynamics Questions and Answers –

# Source Flow

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

**1. In the source flow, the tangential velocity component is _________**

**a) 0**

b) 1

c) not defined

d) infinity

**Explanation:** The velocity component in the source flow is exclusively in the radial direction (Vr). The velocity’s tangential component (Vt) is zero.

**2. ___________ is the scalar function of the space and time.**

a) velocity

**b) velocity potential function**

c) velocity vector

d) pressure

**Explanation:** The scalar function of space and time whose negative derivative with respect to any direction gives the fluid velocity in that direction is known as the velocity function. phi () is the symbol for it. = f is the mathematical expression for it (x,y,z).

**3. 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.**

**4. 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**.

**5. ______ gives the velocity component at right angles to a particular direction.**

a) velocity

b) velocity vector

**c) stream function**

d) pressure line

**Explanation:** The stream function is a scalar space-time function whose partial derivative with respect to any direction yields the velocity component at right angles to that direction. It is denoted by and is only valid for 2D flow.

**6. When velocity potential (ϕ) exits, the flow is _________**

a) rotational

**b) irrotational**

c) laminar

d) turbulent

**Explanation:** When the rotational components are zero, the flow is moving in a linear direction, and the velocity potential indicates the direction of fluid velocity in that direction. The fluid’s velocity travels in a linear direction in irrotational flow.

**7. 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.

**8. 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:** The flow velocity in a source flow is directed away from the origin. All streamlines are straight lines that vary inversely with distance, meaning that the velocity decreases as the distance rises.

**9. The opposite case of the source flow is ___________**

**a) sink flow**

b) doublet flow

c) source flow

d) source-sink flow

**Explanation**: Sink flow is defined as a flow in which the streamlines are directed towards the origin. The sink flow is the inverse of the source flow. The streamlines are inversely proportional to the distance, therefore as the distance decreases, the velocity rises.

**10. The origin is called as _________**

**a) singular point**

b) multiple point

c) sink point

d) source point

**Explanation:** The divergence of velocity for a source flow is zero everywhere except at the origin, where it is infinite. As a result, the origin is a unique point, which can be interpreted as a discrete source or sink of a certain strength with a corresponding induced flow field around it.

Flows from the Source and Sink A source flow is a radially symmetrical flow field directed outwardly from a common point. The line source, defined as “a line from which fluid appears and flows away on planes perpendicular to the line,” is the central common point. The phrases sink and source are used to describe how direct current flows in an electric circuit. A sinking input or output circuit connects the electric load to ground. The voltage source for the electric load is provided via a sourcing input or output.