On the design of three-dimensional wind tunnel contractions

The present method for the calculation of incompressible inviscid flow through nonaxisymmetric, rectangular cross section ducts is based on a finite difference approximation to Laplace's equation, and is solved by the method of successive overrelaxation. By calculating the flows through a series of contracting shapes that are based on a pair of matched elliptic arcs, it becomes possible to choose such parameters as length, local contraction ratio, position, and magnitude of maximum slope. The reduction of the length of the contraction is noted to reduce its effective length, while increasing the effects of overshoot and undershoot. The testing of numerical method predictions against experiment yielded generally satisfactory results.