- Supersonic wind tunnel
A supersonic wind tunnel is a
wind tunnel that producessupersonic speeds (1.2<M<5)The Mach number and flow are determined by thenozzle geometry. TheReynolds number is varied changing the density level (pressure in the settling chamber). Therefore a high pressure ratio is required (for a supersonic regime at M=4, this ratio is of the order of 10). Apart from that, condensation or liquefaction can occur. This means that a supersonic wind tunnel needs a drying or a pre-heating facility.A supersonic wind tunnel has a large power demand leading to only intermittent operation.Restrictions for supersonic tunnel operation
Minimum required pressure ratio
Optimistic estimate:Pressure ratio the total pressure ratio over normal shock at M in test section:
Examples:
Temperature effects: condensation
Temperature in the test section:
with = 330K: = 70K at = 4
The Mach range is limited by reservoir temperature
Power requirements
The power required to run a supersonic windtunnel is enormous, of the order of 50 MW per square meter of test section. For this reason most wind tunnels operate intermittently using energy stored in high-pressure tanks. These windtunnels are also called intermittent supersonic blowdown wind tunnels (of which a schematic preview is given below). Another way of achieving the huge power output is with the use of a vacuum storage tank. These tunnels are called indraft supersonic wind tunnels.Other problems operating a supersonic wind tunnel include:
*enough supply of dry air
*wall interference effects
*fast instruments needed for intermittent measurementsTunnels such as a
Ludwieg tube have short test times (usually less than one second), relatively highReynolds number , and low power requirements.Further reading
*
ee also
*
Wind tunnel
* Low speed wind tunnel
* High speed wind tunnel
*Hypersonic wind tunnel
*Ludwieg tube
*Shock tube External links
* [http://arc.uta.edu/videos_files/SWT_12202007.wmv "UTA supersonic wind tunnel test(Video)"]
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