Aerodynamics Multiple Choice Questions & Answers (MCQs) on “Vortex Flow”.
1. The free vortex flow forms _________
a) straight lines
b) concentric circles
c) parabola
d) hyperbola
Answer: b
Clarification: The free vortex flow is a circulatory flow of the fluid such that its stream lines are concentric circles. The velocity components for a free vortex flow are Ur and Uθ and is equal to Ur=0 and Uθ=circulation/ 2*pi*r.
2. The following figure is an example of ____________
a) source flow
b) sink flow
c) doublet
d) free vortex flow
Answer: d
Clarification: The above figure shows the concentric circles along with streamlines. Here, the stream function is a function of radius and it is constant value and hence the streamlines are concentric.
3. Except at the origin where r=0, the vortex flow is ___________
a) rotational
b) laminar
c) irrotational
d) turbulent
Answer: c
Clarification: Vortex flow is irrotational everywhere except at the point r=0, where the vorticity is infinite. Therefore, the origin, r=0, is a singular point in the flow field. Here, the origin point represents the singularity point.
4. The strength of the vortex flow can be given by ______________
a) Γ=2*pi*C
b) Γ=2*pi
c) Γ=-2*pi*C
d) Γ=0
Answer: c
Clarification: The circulation for vortex flow can be given by –
Γ=2*pi*C where, C – constant and Γ is the strength of the vortex flow.
When Γ is positive, it means that vortex of positive strength rotates in the clockwise direction and vice versa.
5. The combination of uniform flow and source flow gives ___________
a) flow past a cylinder
b) flow past a half body
c) flow past a full body
d) flow past a wedge
6. The circles with their centre on the X axis _____________
a) eccentric circles
b) concentric circles
c) potential lines
d) equal circles
a) Principle of moments
b) Principle of energy
c) Mass conservation
d) Rayleigh’s principle
Answer: a
Clarification: The centre of pressure can be calculated using a principle of moments which states that the moment of the resultant force about an axis is equal to the sum of moments of the components about the same axis.
8. A body floats on the surface when ____________
a) metacenter is above gravity
b) metacenter is below gravity
c) metacenter is equal to gravity
d) gravity is above metacenter
Answer: a
Clarification: In case of a floating object, the metacenter should always be above gravity. Metacentre is the point about which a body starts oscillating when the body is tilted by a small angle. In the case of a floating body, the weight of an object is equal to the amount of fluid displaced.