An Extended Linearized Inverse Theory for Fully Cavitating Hydrofoil Section Design

A new design theory for fully cavitating hydrofoils is based upon a linearized inverse theory of two-dimensional cavity flows at arbitrary cavitation number. The cavity surfaces are assumed to originate at the leading and trailing edges of the wetted surface. This paper reviews and completes the basic theory, which leads to a parametric design technique. In the resulting design procedure, one specifies the design lift coefficient, the cavitation number and the upper cavity thickness at two points along the profile chord. A prescribed pressure distribution shape is also selected. These quantities determine the profilelesgn, which consists of the upper cavity and wetted surface contours, the design angle of attack, the cavity length, the drag coefficient, the moment coefficient and the lift-to-drag ratio. The chief new feature of the third design procedure is that the designer can now prescribe two points on the cavity surface instead of one as heretofore. Although the designer must observe certain constraints when he specifies these two values of cavity thickness, the new procedure is still found to be more general and more flexible than design procedures studied previously.