Module 5 - Exp Test Facilities

Question 1

What are some flow conditioning devices used to improve flow quality in a wind tunnel?

Answer 1

• Turbulence reduction screens: varied porosity to break down turbulent eddies in flow, can be combined to achieve desired flow
• flow straightening devices: reduce cross-stream velocity components

Question 2

What would we like to know about the turbulence in the flow of a wind tunnel?

Answer 2

• Turbulence intensity: rms of velocity fluctuations divided by mean velocity (typ <0.5%)
• Turbulence scales: size and how long turbulent eddies in the flow last)
• uniformity: how uniform is the turbulence across the test section

Question 3

By diverging the test section walls, what effect is minimized?

Answer 3

Horizontal buoyancy

Question 4

Why are test sections typically large compared to the models used? What other effect is minimized if the model is not streamlined?

Answer 4

Solid blockage, wake blockage is minimized for non-streamlined bodies

Question 5

What are two ways of identifying outliers?

Answer 5

• Use statistics to tell you if this was an errant measurement
• take repeat measurements around the outlier to determine if it is a spurious measurement

Question 6

Starting from where the air enters the wind tunnel, what are the common components?

Answer 6

Bell-mouth inlet
Flow conditioning devices
Contraction
Test sections
Diffuser
Fan
Secondary diffuser
Outlet