Flow Characteristics of an Ultracompact Serpentine Inlet with an Internal Bump

Abstract

An ultracompact serpentine inlet, which contains a compact diffuser as short as 2.3 times the exit diameter, is experimentally and numerically studied. An internal bump is introduced to redistribute the boundary layer flows and suppress the massive flow separation. It is found that two vortex pairs with the same rotating direction appear at the diffuser exit. The abnormal upper vortex pair helps to avoid massive flow separation at the aft part of the diffuser. According to the calculated flow patterns on the symmetry plane, it is found that a small reversed flow region appears near the lee side of the bump. The skin-friction line plots on the top and bottom surfaces indicate that three-dimensional flow separation occurs. Three vortex tubes are obtained in the diffuser by the Q-criterion. The first, which develops along the spanwise direction downstream of the bump, induces the reversed flow. The second and third vortex tubes, which originate from the sides of the top and bottom surfaces of the duct, collect the low-momentum fluids and transport them downstream spirally. At a test Mach number of 0.70, the total pressure recovery is 0.987 and 0.944 at exit Mach numbers of 0.253 and 0.491, respectively.