1. What types of visualization is used to delay the separation of the flow?
a) PVT
b) Surface oil film technique
c) Smoke flow visualization
d) Shadow projecting
Explanation: Smoke flow visualization has been used by bakic and peric to visualize the delayed separation of the flow over a smooth sphere. The flow separation occurs when the boundary layer travels far enough against an adverse pressure gradient.
2. How drag is formed on the cylinder?
a) Due to viscous effect
b) Due to friction
c) Due to boundary layer
d) Due to surface layer
Explanation: Drag is due to a viscous effect, which generate a frictional shear stress at the body surface and which causes the flow to separate from the surface on the back of the body. At the leading edge of the cylinder, a stagnation point is formed. Where the oncoming flow is brought to rest. The pressure here is equal to the stagnation pressure. At the adjacent to the cylinder surface, a thin boundary layer is formed. Which causes the drag on the cylinder
3. What is the lift on the cylinder?
a) One
b) Zero
c) Negative
d) Greater than zero
Explanation: Pressure distribution over the top half of the cylinder is equal to the pressure distribution over the bottom half and hence the lift must be zero. The air flows on the cylinder is deflected the same amount upward as the flow is deflected downwards at the rear of the cylinder. So the up wash equalizes the downwash in terms of resulting reaction forces. In the end, the free stream hasn’t been deflected at all but still, lift exists
4.What is the position of stagnation point, when a cylinder is placed in the wind tunnel?
a) Lower part
b) Upper part
c) Middle part
d) No stagnation point
Explanation: The stagnation point moves to the lower part of the cylinder, similar to the theoretical flow. If the spin is sufficiently increased the stagnation point lifts off the surface. Position of stagnation point is a strong function of circulation, with zero circulation stagnation point lies at zero.
5. How the finite lift is measured in the cylinder?
a) Moving up and down
b) Moving up
c) Moving left and right
d) Spinning cylinder
Explanation: A finite lift is measured for the spinning cylinder in the wind tunnel. The friction between the fluid and the surface of the cylinder tends to drag the fluid near the surface in the same direction as the rotational motion.
6. What is the flow of velocity at the top of the cylinder?
a) Higher
b) Lower
c) Constant
d) Does not varies
Explanation: On the top of the cylinder usual non-spinning flow this extra velocity contribution creates a higher than usual velocity at the top of the cylinder and a lower than usual velocity at the bottom. These velocities are assumed to be just outside the viscous boundary layer on the surface from Bernoulli’s equation.
7. Is flow over a circular cylinder can produce a finite lift?
a) True
b) False
Explanation: The pressure imbalance creates a net upward force that is a finite lift. Therefore flow over a circular cylinder can produce a finite lift, from Bernoulli’s equation that as the velocity increases, and the pressure decreases and hence the pressure on the top of the cylinder is lower than on the bottom. This pressure imbalance will create a net upward force, i.e. a finite lift.
8. Is Kutta-Joukowski theorem is fundamental theorem of aerodynamics?
a) True
b) False
Explanation: The Kutta-Joukowski theorem is a fundamental theorem of aerodynamics, this can be used for calculating of lift of an airfoil, or of any two-dimensional bodies including circular cylinders translating in a uniform fluid at a constant speed large enough so, that the flow seen in the body is fixed frame is steady and unseparated.
9. Is Kutta-Joukowski theorem relate to lift?
a) False
b) True
Explanation: The Kutta-Joukowski theorem relates the lift generated by an airfoil, to the speed of the airfoil. Through the fluid, the density of the fluid and the circulation. This theorem relates lift to circulation much like the Magnus effect relates to side force to the rotation
10. Define circulation.
a) Line integral around a closed loop enclosing the airfoil
b) Line integral around an open loop enclosing the airfoil
c) Line integral around an in loop enclosing the airfoil
d) Line integral of airfoil
Explanation: Circulation is defined as the line integral around a closed loop enclosing the airfoil of the component of the velocity of the fluid tangent to the loop. To calculate the force on an airfoil, outside the boundary layer the vorticity is zero, everywhere the circulation is the same around every circuit