Engineering Questions with Answers - Multiple Choice Questions

Aerodynamics – The Vortex Filament, Biot-Savart Law, Helmholtz Theorem – 2

1 - Question

Is vortex filament is a very thin strip?
a) True
b) False
View Answer Answer: a
Explanation: A vortex filament is a very thin strip of vorticity in x-y plane. The small thickness assumption will be used to characterize the filament by its center line curve. Mass conservation and material transport of vorticity are used to describe variation in local thickness and vorticity.



2 - Question

Is thin strips of vorticity are unstable to disturbances and tend to roll up?
a) False
b) True
View Answer Answer: b
Explanation: Vortex filament is well known that thin strip of vorticity are unstable to disturbance and tend to roll up. Here we test this using our model, we study two cases a parabolic vortex filament and a circular vortex filament.



3 - Question

Is weak external velocity, rolling up of the vortex filament?
a) True
b) False
View Answer Answer: a
Explanation: The weak external velocity, rolling up of the vortex filament occurs as expected, but in the presence of strong external velocity field, the filament is extremely stretched out and flattened, preventing all rolling up activities.



4 - Question

Is circular filament is of constant thickness?
a) True
b) False
View Answer Answer: a
Explanation: The closed filaments, a circular filament of constant thickness and vorticity is in self equilibrium, this is easily verified using z=e, consider straight filaments placed on the z-axis with constant vorticity along the curve.



5 - Question

Is vortex filament equation can be modified to include the effects of point vortices?
a) False
b) True
View Answer Answer: b
Explanation: The vortex filament equation can be modified to include the effects of point vortices, here we place two point vortices symmetrically inside a circular vortex filament. Initially, the point vortices just rotate about the center of the circular vortex filament.



6 - Question

Is Helmholtz’s theorems apply to inviscid flows?
a) True
b) False
View Answer Answer: a
Explanation: Helmholtz’s theorems apply to inviscid flows, in observation of vortices in real fluid the strength of the vortices always decays gradually due to the dissipative effect of viscous forces. Thus, it only applied to inviscid flows.



7 - Question

Is strength of a vortex tube vary with time?
a) False
b) True
View Answer Answer: a
Explanation: The strength of a vortex tube does not vary with time, fluid elements lying on a vortex line at some instant continue to lie on that vortex line. More simply, vortex lines move with the fluid, also vortex lines and tubes must appear as a closed loop.



8 - Question

Is Biot-savart law is used for computing the resultant magnetic field?
a) True
b) False
View Answer Answer: a
Explanation: The biot-savart law is used for computing the resultant magnetic field at position r in 3D –space generated by a steady current. Steady current is a continual flow of charges which does not charge wit time and the charge neither accumulates nor depletes at any point.



9 - Question

Is integral is usually around a closed curve?
a) True
b) False
View Answer Answer: c
Explanation: The integral is usually around a closed curve since stationary electric currents can only flow around closed paths when they are bounded. However, the law also applies to infinitely long wires as used in the definition of the SI unit of electric current.



10 - Question

Is 2D version of Biot-Savart equation is used, when the sources are invariant in one direction?
a) True
b) False
View Answer Answer: a
Explanation: The 2D version of the biot-savart equation is used when the sources are invariant in one direction.in general the current need not flow only in a plane normal to the invariant direction and it is given by the formulations given above work well when the current can be approximated as running through an infinitely-narrow wire.

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