to test models of proposed aircraft.
In the tunnel, the engineer can carefully control the
flow conditions which affect
on the aircraft. By making careful
of the forces on
the model, the engineer can predict the forces on the full scale
aircraft. And by using special
techniques, the engineer
can better understand and improve the performance of the aircraft.
Wind tunnels are usually designed for a specific purpose and speed
range. There are special tunnels for
subsonic, supersonic, and hypersonic
flight, and even full scale testing.
A wind tunnel may be
and draw air from outside the tunnel into
the test section and then exhaust back to the outside, or the tunnel may be
with the air
recirculating inside the tunnel. The tunnel in the figure is a
closed tunnel which we are viewing from above.
The air inside the tunnel is made to move by the
on the far side of the tunnel.
In this figure, air continuously moves
counter-clockwise around the circuit,
passing over the
that is mounted in the test section.
The model is instrumented to provide the engineer with test data. To obtain
meaningful data, the engineer must insure that the flow
match the desired flight conditions. Both the Mach number and the Reynolds number
depend on the velocity and gas density in the tunnel.
For safety reasons, engineers can not be present in the test section during the
operation of the tunnel. The engineers
the tunnel from a
in an adjoining building. Data from the
model is transferred to the control room through bundles of electrical lines.
- Beginner's Guide Home Page