Electroforming of Venturi-Type Nozzles for Wind Tunnels and Other Applications

The electroforming of venturi nozzles is described to demonstrate that the electroforming process may be used as a method of specialized and close-tolerance electrochemical fabrication. The principle of the venturi (see Fig. 1) is a basic physical fact: when fluids are forced through a restricted orifice the velocity of the fluid flow is correspondingly increased, thereby also causing a proportional pressure drop. In the present Space Age, the importance of the venturi is manifold. Practical examples include such highly significant devices as thrust chambers, attitude control rocket engines and nozzles, and wind tunnel nozzle liners. Specifically in the wind tunnel area are included axisymmetric hypersonic, hyperthermal, and hypervelocity impulse nozzles. As the speed of aircraft increased, aerodynamic design requirements prompted vast improvements in the wind tunnel. From the first relatively crude subsonic wind tunnel design, demands necessitated constant improvement of performance, control, and speed. This prompted the development of the stationary rectangular throat tunnel, and then the flex-type throat tunnel. Continued advances in aircraft and missile performance demanded improved wind tunnel design from subsonic to trisonic to supersonic and finally to the hypersonic speed test tunnels. Necessarily, wind tunnel design concepts changed from the flex-type or rectangular to the axisymmetric or round type, and as the Mach number requirements increased, the internal fluid contour dimensional tolerances became more and more exacting.