# Aerodynamics Questions and Answers – Doublet Flow

This set of Aerodynamics Multiple Choice Questions & Answers (MCQs) focuses on “Doublet Flow”.

1. When velocity potential (Φ) is constant, it is called as _________
a) velocity line
b) velocity curve
c) potential line
d) equipotential line

Explanation: The line along which the velocity potential (Φ) is constant is called a equipotential line. For an equipotential line,
Φ=constant and also dΦ=0
The slope for the equipotential line can be given as=dy/dx.

2. Series of equipotential lines and streamlines is ________
a) flow net
b) constant flow
c) equilibrium flow
d) positive flow

Explanation: The grid obtained by drawing a series of equipotential lines and stream lines is called a flow net. A flow net is an important tool in analyzing two-dimensional flow problems.

3. When both the source and sink are of equal strength it is called ________
a) sink
b) source
c) doublet
d) positive derivative of flow

Explanation: Doublet is the special case of source and sink with equal strength. Let q and -q be the strength of source and sink respectively. Let 2a be the distance between the source and sink and it approaches zero. The product 2a*q is called as doublet strength.

4. When the amount of fluid displaced is equal to weight of body, it is called as _______
a) metacentre
b) buoyancy
c) centre of buoyancy
d) centre of gravity

Explanation: When a body is immersed in a fluid, an upward fluid is exerted by the fluid on the body. This upward force is equal to the weight of the fluid displaced by the body and is called as buoyancy or the force of buoyancy.

5. Which of the following is suitable for the jet of oil in an unbroken stream?
a) temperature
b) surface tension
c) capillarity
d) vapour pressure

Explanation: The surface tension is the property of a fluid which occurs because of the cohesive force between the molecules of the fluid. In a jet of oil, the molecules of oil and the air interact and also the molecules of the oil try to acquire the minimum area.
Sanfoundry Certification Contest of the Month is Live. 100+ Subjects. Participate Now!

6. The ratio of Inertia force to elastic force is called as ________
a) Reynold’s number
b) Froude number
c) Weber number
d) Mach number

Explanation: The inertial force is given by-ρ*L2*V22 and the elastic force is given by- K*X*A.
Therefore, the mach number is given by- ρ* L2* V2/K*X*A which gives, V2/(K/ρ).

7. The sound which can be related to explosion in human ears is _____
a) high frequency sound
b) low frequency sound
c) boom
d) sonic boom

Explanation: The sound which is related to shock waves that are created by the object travelling faster than the speed of sound is called a sonic boom. When an aircraft travels with a high speed, series of pressure waves are also created and these when combine together leads to sonic boom.

8. When the velocity at a point becomes zero, it refers to ___________
a) slip condition
b) no slip condition
c) positive slip condition
d) negative slip condition

Explanation: At the boundary of solids, the velocity at a point becomes zero. Dirichlet’s condition is an example of no slip-condition. When the adhesive forces are stronger than cohesive force the particle does not move and hence no slip-condition occurs.

9. Density is ratio of __________
a) mass to volume
b) volume to mass
c) mass to pressure
d) pressure to volume

Explanation: Density is the ratio of mass to volume and is measured in kilograms per meters cube. The density of the liquids remains constant while the density of gases changes with the variation of pressure and temperature.

10. The units of viscosity are __________
a) N/m
b) Ns/m2
c) m/s
d) Dimension less quantity

Explanation: The viscosity is defined as the property of the fluid which offers resistance to the movement of one layer over the other layer. It is shear stress required to produce unit rate of shear strain that is force*time/length2 that is Ns/m2.

Sanfoundry Global Education & Learning Series – Aerodynamics.

To practice all areas of Aerodynamics, here is complete set of 1000+ Multiple Choice Questions and Answers.