An Experimental Investigation of the Design Variables for NACA Submerged Duct Entrances

An investigation was made of entrance width-to-depth ratio, ramp-wall divergence, ramp angle, and other variables affecting an NACA submerged duct design. Tests were also conducted to show the effect of variation of boundary-layer thickness. Results indicate that an optimum NACA submerged-inlet design should employ a width-to-depth ratio of from 3 to 5, curved diverging ramp walls, and a 5 to 7 deg ramp angle. The boundary-layer thickness of the surface into which the inlet is placed was found to have a large effect on the pressure recovery.