Supersonic wind tunnel

A supersonic wind tunnel is a wind tunnel that produces supersonic speeds (1.2<M<5)The Mach number and flow are determined by the nozzle geometry. The Reynolds 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 $leq$ the total pressure ratio over normal shock at M in test section:

$frac\{P\_t\}\{P\_\{amb\; leqleft(frac\{P\_\{t\_1\{P\_\{t\_2\; ight)\_\{M\_1=M\_m\}$

Examples:

Temperature effects: condensation

Temperature in the test section:

$frac\{T\_m\}\{T\_t\}=left(1+frac\{gamma-1\}\{2\}M\_m^2\; ight)^\{-1\}$

with $T\_t$ = 330K: $T\_m$ = 70K at $M\_m$ = 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 measurements

Tunnels such as a Ludwieg tube have short test times (usually less than one second), relatively high Reynolds 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)"]