Abstract
The 3-inch high-speed wind tunnel developed by Stanton has been converted in the Engineering Department of the National Physical Laboratory to the open jet principle, the working jet now being contained in a square glass-sided chamber. The pressure in the observation chamber can be controlled within certain limits by altering the axial length of the gap between the inlet and outlet, and the presence of standing waves in the jet can be largely eliminated by bringing the chamber pressure to a value equal to that in the jet at the chamber inlet.
In place of the divergent jet used by Stanton, an approximately parallel working jet has been obtained in the modified tunnel by using inlet nozzles with profiles determined by a graphical construction based on the “characteristic curve” method given by Busemann. An optical system has also been fitted enabling Schlieren photographs of the flow pattern to be obtained. Measurements of the wave systems set up round model cones indicate agreement with the theory established by Taylor and Maccoll which they found to accord with the results of larger-scale firing trials on conical-headed shell, thus providing evidence of the close similarity between conditions in the tunnel and on the full scale.
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