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Obtaining supersonic airflow in transonic wind tunnels and sliced wall perforation in the test section
Borivoj Blizanac, PhD
By an apropriate modeling of partially opened walls of a wind tunnel, Mach number in the test section can be increased even after air stream sonic velocity has been achieved. This is achieved by conducting air stream to the test section chambe. For conventional supersonic wind tunnels, supersonic Mach numbers can be obtained by placing the supersonic nozzle in front of the test section, the contour (shape) of which is being characteristic for each Mach number. Change in supersonic nozzle contour is very small for a Mach number close to one, thus making small changes in a Mach number for the closed test section impossible. Additionally, after taking into consideration more difficult compensation of the boundary layer in the test section for these small changes in the gradient of Mach number (when M≈1), a need for air removal from the test section into the test section chamber of a transonic wind tunnel becomes even more pronounced.
Key words: transonic wind tunnel, test section, supersonic flow, Mach number.
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