# Aerodynamics Questions and Answers – Circulation

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

1.The line integral of a closed curve around of a velocity field is defined as____________
a) Vorticity
b) Circulation
c) Dilatation
d) Streamline

Explanation: Circulation is the line integral of the velocity around a closed curve in the flow. It depends on the velocity field and the selection of the curve. It defines the movement of the flow inside the curve. It is given by-
Γ=∮c V. ds where, Γ- circulation, ∮c – curve, V.ds – velocity field.

2. If the flow is irrotational everywhere within the contour of integration then the circulation is ____________
a) 1
b) positive
c) negative
d) zero

Explanation: In the case of irrotational flow, the circulation about a curve is equal to the vorticity integrated over any open surface bounded by the curve. This leads to the result that if the flow is irrotational everywhere, the circulation is zero.

3. The component of vorticity normal to dS is equal to __________
a) circulation per unit area
b) negative of circulation per unit area
c) zero
d) circulation

Explanation: The relation between circulation and vorticity can be given by-
(∇*V).n = -dΓ/dS
Where dS – infinitesimal area enclosed
C – Infinitesimal curve.

4. Circulation is referred to as _____________
a) divergence of velocity
b) velocity field
c) flux of vorticity
d) velocity

Explanation: Using Stoke’s theorem, the line integral of velocity field along a closed curve is equal to the surface integral of velocity field along a closed path normal to the area covered by the path. But we know that curl of velocity is called vorticity and hence, the circulation is called a flux of vorticity.

5. Which of the following has more viscosity?
a) Water
b) Honey
c) Oil
d) Juice

Explanation: Honey has more viscosity. Viscosity is the measure of the resistance offered by the flow to the shear or tensile stress. The relative motion between the two surfaces moving with different velocities is given by viscosity.
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6. The boundary layer is formed at the _____________
a) boundary of an object
b) surface of an object
c) at a point on an object
d) edges of an object

Explanation: The boundary layer is formed at the boundary of an object. The boundary layer divides the flow into two parts- Viscous and inviscid. The flow inside the boundary layer is highly viscous whereas, the flow outside the boundary is inviscid flow.

7. The nature of the boundary layer depends on _____________
a) Mach number
b) Inertia force
c) Reynold’s number
d) Viscosity

Explanation: The nature of the boundary layer depends on Reynold’s number which is the ratio of inertial force to viscous force. Depending on the value of Reynold’s number, the boundary layer may be laminar (the flow is continuous) or it may be turbulent ( the flow is discontinuous).

8. In microscopic view, Circulation is a __________ quantity.
a) vector
b) dimension less
c) scalar
d) non-measurable

Explanation: In a macroscopic view, circulation is a scalar quantity as it is defined as the line integral of velocity field over a closed region. In a microscopic view, circulation is a flux of vorticity, which makes it a vector quantity.

Sanfoundry Global Education & Learning Series – Aerodynamics.