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What are the speeds for testing wind tunnels?
Wind tunnels move air at different speeds. Some are best for testing objects at less than 200 miles per hour. Others move air at more than five times the speed of sound (about 4,000 mph). Many wind tunnels use fans to speed up the air.
What is Mach number in wind tunnel?
Wind tunnels are often denoted by the speed in the test section relative to the speed of sound. The ratio of the air speed to the speed of sound is called the Mach number. Tunnels are classified as subsonic (M < . 8) , transonic (.
How do you measure velocity in a wind tunnel?
In many wind tunnel tests, mean velocity in the test section is determined indirectly, by measuring stagnation and static pressures. One or several pressure probes can be used in these measurements. Velocity field in the wind tunnel test section can be determined based on the measurement of pressure distribution.
How is the Mach number used in wind tunnel testing?
The Mach number appears as a similarity parameter in many of the equations for compressible flows , shock waves , and expansions . When wind tunnel testing, you must closely match the Mach number between the experiment and flight conditions.
How is the speed of sound measured in a wind tunnel?
When wind tunnel testing, you must closely match the Mach number between the experiment and flight conditions. It is completely incorrect to measure a drag coefficient at some low speed (say 200 mph) and apply that drag coefficient at twice the speed of sound (approximately 1400 mph, Mach = 2.0).
What do you need to know about wind tunnel testing?
In wind tunnel testing you need to match several similarity parameters; the most well known are the Reynolds number and the Mach number.
Is the Mach number of an object equal to the speed of sound?
As the speed of the object approaches the speed of sound, the flight Mach number is nearly equal to one, M = 1 , and the flow is said to be transonic . At some places on the object, the local speed exceeds the speed of sound.