REPORT NO. 875 APPLICATION OF THE ANALOGY BETWEEN WATER FLOW WITH.4 FREE SURFACE AND TWTO-DIhfENSIONAL COMPIWWBLE GAS FLOW

The theory of ~ke hydraulic analogy—tha ~ is, the analogy betuwn water jimo m“th a free surface and two-dimensional compressiblegasflvw--and the limitations and conditions of the analogy are discussed..4 test was run wing the hydraulic analogy as applied to the~ow about circular cylinders of rarious diameters at subsonic velocities extending into the supercritical range. The apparatue and ~echniquesused in this application are described and cri~icized. Reasonably satisfactory agree-ment of pressure distributions and jlow jteld.s existed between water and air$ow about corresponding bodies. This agreement indicated the possibility of e.rkn.dingexperimental compressi-bildy research by new methods. LNTRODUCTIOX.&n analogy exists between water flo-iv with a free surface aml two-dimensional compressible gas flow (hydraulic amdogy). The water must flow over a smooth horizonta