# Aerodynamics Questions and Answers – Viscous Flow – 1

This set of Aerodynamics Multiple Choice Questions & Answers (MCQs) focuses on “Viscous Flow – 1”.

1. Is thin viscous region forms over the airfoil at low angle of attack?
a) True
b) False

Explanation: At low angle of attack, a thin viscous region forms over the airfoil, and grows from the leading edge to the trailing. On the upper surface, where adverse pressure gradients exists the boundary layer grows more rapidly.

2. Is outer flow over an airfoil has less camber than the original airfoil?
a) False
b) True

Explanation: The outer flow sees an equivalent airfoil that has less camber than the original airfoil, due to the disproportionate growth of the boundary layer on the two side and that has an open trailing edge. Such an airfoil produce less lift than the original airfoil.

3. Is lift is generated due to large pressure gradients on the upper side of the airfoil?
a) True
b) False

Explanation: At higher angles, very large adverse pressure gradients that develop on the upper side as the airfoil attempts to generate more lift causes the boundary layer to separate, leading to a major disruption of the flow over the airfoil and the wing stalls.

4. Is lift loss with increase in angle of attack?
a) True
b) False

Explanation: The loss in lift which does the increase in the angle of attack, in most instances stall occurs gradually, with a slow upward motion of the separation of the boundary layer from the trailing edge to the leading edge.

a) True
b) False

Explanation: In some airfoils with small leading edge radius the stall is rather abrupt. The flow is well behaved at an angle of attack, say 5.5 degrees, but stalls with flow separation at the leading edge at 5.6 degrees because of the high adverse pressure gradient that occurs at such sharp leading edge.

6. Is boundary layer, the phenomenon of stall and the location of separation point plays a critical role?
a) True
b) False

Explanation: The growth of the boundary layer the phenomenon of stall and the location of the separation point thus play a critical role. This course attempts to develop theories and methods by which these quantities can be computed, given the pressure distribution over the airfoil.

7. Is drag coefficient of the airfoil is affected by viscous effect?
a) True
b) False

Explanation: Some shapes have less drag than others. The drag coefficient is seen to the first drop with lift, then rise. These phenomena cannot be explained on the basis of inviscid potential flow theory which will cause the viscous effect.

8. Is interface between the solid and fluid, shear stresses develop as the solid attempts to slow down the fluid flowing?
a) True
b) False

Explanation: The interface between the solid and fluid, shear stresses develop as the solid attempt’s to slow down the fluid flowing over it. This shear stress gives rise to a skin friction drag. It is proportional to the product of a quantity called viscosity.

9. Is viscosity effects the pitching moments?
a) True
b) False

Explanation: Viscosity also affects the pitching moments of an airfoil. The pitching moment coefficient of an airfoil about chord point, potential flow theory states that this coefficient about this point is zero. In reality, a nose down pitching moment develops at a high angle of attack as the lift distributed over the nose part of the airfoil decrease due to viscous effects.

10. Is a viscous effect play a major role in flows of intersect?
a) True
b) False

Explanation: Viscous effect play a major role in other flows, of intersect such as flow through compressors, turbines and diffusers and in non- aerospace applications as well. In all these applications, the raised by the designer and the engineer are often the same.

Sanfoundry Global Education & Learning Series – Aerodynamics.

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