Drag Reduction of a Cylinder/Endwall Junction Using the Iceformation Method

The iceformation design method was used to reduce the drag of a juncture between a cylinder and flat endwall. Ice was formed on a subfreezing flat endwall in a warmer laminar water flow. The ice shape was influenced by and altered the three-dimensional separated boundary layer and the cylinder wake. Preliminary experiments were used to indicate control parameter relationships. An adaptive selection theory was used to determine optimal control parameters. A sample optimal contour was generated and tested for juncture drag performance. High Reynolds number wind tunnel drag tests showed that the iceform contour had an average of 18 percent lower drag than a flat plate juncture given the same upstream boundary layer conditions. Flow visualizations showed that the iceform contour produced three larger diameter vortices compared to the laminar four vortex model of Baker (1979).