Contraction and Flexible Nozzle

Contraction

The contraction squeezes and accelerates the flow from the Flow Smoothing Honeycomb into the Flexible Nozzle. The shape of the tunnel changes from an octagon at the honeycomb to a rectangle at the nozzle and the cross-sectional area at the nozzle is over 11 times smaller than that at the honeycomb.

Flexible Nozzle

The flexible nozzle can change its shape depending on the air speed needed in the Test Section. The sonic nozzle shape is used for subsonic speeds. For supersonic speeds above Mach 1.15, the nozzle is squeezed into a convergent-divergent shape which accelerates the airflow from subsonic to supersonic speeds.

Technical Information

The sonic nozzle shape is used for all Mach numbers up to 1.12. Air speeds above Mach 1 are achieved with Auxiliary Suction which removes air through the perforated walls of the Test Section to increase the effective cross-sectional area available to the flow. This increase in cross-sectional area expands the flow in the test section from sonic to supersonic speeds.

At higher supersonic speeds, the airflow is accelerated through a convergent-divergent nozzle shape which has discrete settings from Mach 1.15 to Mach 1.40 in increments of 0.05.

The nozzle shape at each setting is defined by 20 jacking points on the upper and lower flexible walls, and a cam operating mechanism (pictured) drives the walls from one setting to the next.