Automatic setting of the flexible walls of a large wind tunnel

To develop supersonic air flow in a wind tunnel it is usual to provide a nicely contoured constriction in the air passage ahead of the model test region, and it is necessary to alter the cross-section of this `throat¿ to cater for different air speeds. In the tunnel under consideration, the constriction is formed by two flexible steel plates, sliding between side walls and constrained to the required adjustable profile by a series of hydraulically-actuated screw jacks. The paper deals with the electrical control system, for storing the necessary jack-setting data on punched tape, and releasing it to govern, simultaneously, the motion of every screw jack with the required degree of precision, so that the shape of the aerodynamic throat can be adjusted progressively throughout the air-speed range of the tunnel. In developing the system, a number of pieces of electro-mechanical equipment had to be devised. Some of this new apparatus is briefly described, and its operation is indicated.