Why are wind tunnels Pressurised?

High Reynolds number tunnels Pressurised tunnels: Here test gases are pressurised to increase the Reynolds number.

What is the role of a second throat in a supersonic wind tunnel?

A second throat is often employed downstream of the test section to shock down the supersonic flow to subsonic before entering the low pressure chamber. The indraft tunnel uses the low pressure (vacuum) chamber downstream of the test section to produce flow.

What are the basic principles for wind tunnel selection?

A good quality wind tunnel will have a flow uniformity of 0.5-2% and turbulence intensity of 0.5-2%. It should provide temperature uniformity within 0.1-0.5oC at the inlet of the test section [1].

What do you mean by transonic wind tunnel?

The Transonic Wind Tunnel is used to study high-speed aerodynamic flows around aircraft and to investigate how these flows interact with the stores and other attachments carried and released from the wings and fuselage. Studies are conducted using sub-scale models.

What are the classifications of wind tunnel balances?

Types of Wind Tunnel Tests

• Six component force tests. In these tests a model is mounted near the center of the test section and aerodynamic forces and moments are measured at various combinations of pitch and yaw angles at a constant airspeed.
• Internal balance tests.
• Pressure tests.
• Flow Visualization Tests.

What are the two basic types of wind tunnel?

Wind Tunnel Test There are basically two types of wind tunnel test which are static stability and the pressure test. With these two tests, you can determine the aerodynamic characteristics of the aircraft.

When is a wind tunnel called a subsonic wind tunnel?

If the maximum speed ac hieved by the wind tunnel is less than the speed of sound in air, it is called a subsonic wind tunnel. The speed of sound in air at room temperature is approximately 343 m/s, or 1235 km/hr, or 767 mile/hr.

What happens to the flow in a wind tunnel?

For a subsonic wind tunnel, the flow downstream of the test section will decelerate and stay subsonic. For a supersonic flow (M > 1) the term multiplying velocity change is negative ( [1 – M^2] < 0).

What is the Mach number of a transonic wind tunnel?

The Mach number is approximately 1 with combined subsonic and supersonic flow regions. Testing at transonic speeds presents additional problems, mainly due to the reflection of the shock waves from the walls of the test section (see figure below or enlarge the thumb picture at the right).

What is the speed of sound in a wind tunnel?

Subsonic wind tunnels. If the maximum speed ac hieved by the wind tunnel is less than the speed of sound in air, it is called a subsonic wind tunnel. The speed of sound in air at room temperature is approximately 343 m/s, or 1235 km/hr, or 767 mile/hr.