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P. Liu
6.3 Low-Speed Wind Tunnel
A wind tunnel in which the compressibility of air is negligible is called lowspeed wind tunnel. In terms of the size of the test section (referring to the
equivalent diameter of the cross-sectional area of the test section), there are
micro low-speed wind tunnels of tens of millimeters, small low-speed wind
tunnels of 1−1.5 m mainly used for teaching and researching, medium lowspeed wind tunnels of 2−4 m (most aviation wind tunnels of 3 m), and
large low-speed wind tunnels of over 8 m. Large wind tunnels in which real
aircraft or full-size models can be put into a test section are called full-size
wind tunnels. The power of the fan motors that drive the airflow in a lowspeed wind tunnel is only a few hundred watts. In addition to low-speed
aerodynamic tests of aircraft, low-speed wind tunnels can also be used for
low-speed aerodynamic tests of recoverable satellites, spacecraft, and the final
stages of the shuttle re-entry process. In the non-aerospace field, low-speed
wind tunnels are also needed for the study of vehicle air resistance, wind load
and wind vibration of buildings and structures, wind energy development
and research, as well as the study of air pollution, cold and heat, rain and
snow, light, dust storms, and storms.
1. Low-speed wind tunnel
There are two basic forms of low-speed wind tunnel: blow-down and
loop. According to the different structures of the test section, it can be
divided into open-jet and closed-section. The boundary of the closedsection wind tunnel is the solid wall and the boundary of the open-jet
is the free boundary. Most low-speed wind tunnels in the world are loop
wind tunnels. The difference between the loop and blow-down wind
tunnels is the extra reflux channel. The main function of the reflux channel
is to make the airflow in the wind tunnel free from the interference of the
outside atmosphere, so that the temperature can be controlled and noise
pollution can be reduced. The blow-down wind tunnel is vulnerable to
the interference of the outside atmosphere (referring to the large direct
flow wind tunnel with the inlet and outlet outside, which will be affected
by a gust, rain, snow, and foreign matters if no measures are taken), and
the noise will pollute the environment. The pressure in the test section is
lower than the pressure in the atmosphere outside the tunnel. These are
the downsides of straight wind tunnels. The advantages of a blow-down
wind tunnel are that the large transverse flow changes generated during
the vertical short-takeoff and landing aircraft test will not lead to backflow,
and the engine can run in clean air without the problems of air temperature rise and cooling in the wind tunnel. Blow-down wind tunnels are
P. Liu
6.3 Low-Speed Wind Tunnel
A wind tunnel in which the compressibility of air is negligible is called lowspeed wind tunnel. In terms of the size of the test section (referring to the
equivalent diameter of the cross-sectional area of the test section), there are
micro low-speed wind tunnels of tens of millimeters, small low-speed wind
tunnels of 1−1.5 m mainly used for teaching and researching, medium lowspeed wind tunnels of 2−4 m (most aviation wind tunnels of 3 m), and
large low-speed wind tunnels of over 8 m. Large wind tunnels in which real
aircraft or full-size models can be put into a test section are called full-size
wind tunnels. The power of the fan motors that drive the airflow in a lowspeed wind tunnel is only a few hundred watts. In addition to low-speed
aerodynamic tests of aircraft, low-speed wind tunnels can also be used for
low-speed aerodynamic tests of recoverable satellites, spacecraft, and the final
stages of the shuttle re-entry process. In the non-aerospace field, low-speed
wind tunnels are also needed for the study of vehicle air resistance, wind load
and wind vibration of buildings and structures, wind energy development
and research, as well as the study of air pollution, cold and heat, rain and
snow, light, dust storms, and storms.
1. Low-speed wind tunnel
There are two basic forms of low-speed wind tunnel: blow-down and
loop. According to the different structures of the test section, it can be
divided into open-jet and closed-section. The boundary of the closedsection wind tunnel is the solid wall and the boundary of the open-jet
is the free boundary. Most low-speed wind tunnels in the world are loop
wind tunnels. The difference between the loop and blow-down wind
tunnels is the extra reflux channel. The main function of the reflux channel
is to make the airflow in the wind tunnel free from the interference of the
outside atmosphere, so that the temperature can be controlled and noise
pollution can be reduced. The blow-down wind tunnel is vulnerable to
the interference of the outside atmosphere (referring to the large direct
flow wind tunnel with the inlet and outlet outside, which will be affected
by a gust, rain, snow, and foreign matters if no measures are taken), and
the noise will pollute the environment. The pressure in the test section is
lower than the pressure in the atmosphere outside the tunnel. These are
the downsides of straight wind tunnels. The advantages of a blow-down
wind tunnel are that the large transverse flow changes generated during
the vertical short-takeoff and landing aircraft test will not lead to backflow,
and the engine can run in clean air without the problems of air temperature rise and cooling in the wind tunnel. Blow-down wind tunnels are