Engineering Questions with Answers - Multiple Choice Questions
Aerodynamics – Vortex Flow
The free vortex flow forms _________
a) straight lines
b) concentric circles
Explanation: 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.
The following figure is an example of ____________
a) source flow
b) sink flow
d) free vortex flow
Explanation: 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.
Except at the origin where r=0, the vortex flow is ___________
Explanation: 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.
The strength of the vortex flow can be given by ______________
Explanation: 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.
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
Explanation: When a uniform of velocity U combines with a source flow of strength q, the resultant flow is a flow over a half body.
The circles with their centre on the X axis _____________
a) eccentric circles
b) concentric circles
c) potential lines
d) equal circles
Explanation: Potential lines are eccentric non-intersecting circles with their centres on x-axis. The potential lines for source pair will be eccentric non-intersecting circles.
Centre of pressure can be calculated using __________
a) Principle of moments
b) Principle of energy
c) Mass conservation
d) Rayleigh’s principle
Explanation: 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.
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
Explanation: 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.