2 Quiz BASICS OF AIRFLOW

Which of these statements about a stationary subsonic flow are correct or incorrect? I. The static pressure decreases as the streamlines converge. II. The velocity increases as the streamlines converge.

• I is incorrect, II is incorrect.
• I is incorrect, II is correct.
• I is correct, II is correct.
• I is correct, II is incorrect.

A laminar boundary layer is a layer, in which:

• the temperature varies constantly.
• the velocity is constant.
• no normal to the surface velocity components exist.
• the vortices are weak.

The transition point is where the boundary layer changes from:

• attached flow into separated flow.
• turbulent into laminar.
• laminar into turbulent.
• separated flow into attached flow.

Which type of boundary layer, when considering its velocity profile perpendicular to the flow, has the greatest change in velocity close to the surface?

• Laminar boundary layer.
• No difference.
• The boundary layer in the transition between turbulent and laminar.
• Turbulent boundary layer.

Which of the following statements about boundary layers is correct?

• The turbulent boundary layer gives a lower skin friction than the laminar boundary layer.
• The turbulent boundary layer is thinner than the laminar boundary layer.
• The turbulent boundary layer will separate more easily than the laminar boundary layer.
• The turbulent boundary layer has more kinetic energy than the laminar boundary layer.

On a flat plate behind the transition point in a boundary layer:

• the boundary layer gets thinner and the mean speed increases.
• the mean speed and friction drag increase.
• the mean speed increases and the friction drag decreases.
• the boundary layer gets thicker and the mean speed decreases.

Which statement is correct about the laminar and turbulent boundary layer:

• friction drag is lower in the turbulent layer.
• friction drag will be equal in both types of layers.
• friction drag is lower in the laminar layer.
• separation point will occur earlier in the turbulent layer.

Assuming no flow separation, which of these statements about the flow around an aerofoil as the angle of attack increases are correct or incorrect? I. The stagnation point moves down. II. The point of lowest pressure moves forward.

• I is incorrect, II is correct.
• I is correct, II is incorrect.
• I is correct, II is correct.
• I is incorrect, II is incorrect.