Wind Tunnel Testing Questions and Answers

Assertion (A): Model support interference can be measured and removed from the data.

Reason (R): The sting alters the flow near the model, particularly at the base.

Select the correct answer from the options below.

Assertion (A): Pressure-sensitive paint gives a continuous map of surface pressure.

Reason (R): Its luminescence is quenched in proportion to the local oxygen partial pressure.

Select the correct answer from the options below.

Consider the following statements about closed-circuit wind tunnels:

1. They need less drive power than an open tunnel of the same test section.

2. They give better control of flow quality.

3. They are cheaper to build than an open tunnel.

Which of the statements given above is or are correct?

Consider the following statements about similarity in wind-tunnel testing:

1. Geometric similarity requires the model to have the same shape as the full-scale article.

2. Dynamic similarity requires the governing dimensionless force ratios to match.

3. Matching Reynolds and Mach numbers together is usually straightforward at model scale.

Which of the statements given above is or are correct?

Consider the following statements about wind-tunnel corrections:

1. Solid blockage arises from the volume the model occupies.

2. Wake blockage arises from the velocity deficit behind the model.

3. Horizontal buoyancy arises from the weight of the model.

Which of the statements given above is or are correct?

Consider the following statements about raising the Reynolds number in a tunnel:

1. Pressurising the circuit raises it in proportion to the density.

2. Cooling the gas raises it by increasing density and reducing viscosity together.

3. Increasing the test speed raises it without any other consequence.

Which of the statements given above is or are correct?

Consider the following statements about flow visualisation techniques:

1. Schlieren responds to the density gradient.

2. Surface oil flow reveals the skin-friction line pattern.

3. Particle image velocimetry measures surface pressure.

Which of the statements given above is or are correct?

Consider the following statements about supersonic wind tunnels:

1. The nozzle area ratio fixes the test-section Mach number.

2. A second throat downstream reduces the drive power needed.

3. The test-section Mach number can be varied by changing the fan speed.

Which of the statements given above is or are correct?

Consider the following statements about a blowdown tunnel:

1. It runs for a limited time from a charged reservoir.

2. Conditions drift as the reservoir empties.

3. It costs more to build than a continuous tunnel of the same performance.

Which of the statements given above is or are correct?

Consider the following statements about test-section blockage:

1. It causes the measured forces to come out too high if uncorrected.

2. Frontal area is usually kept below about five per cent of the section area.

3. It can be ignored entirely if the model is well streamlined.

Which of the statements given above is or are correct?