Project Highlight

Low Speed Aerodynamics

Control of flow separation in air intakes via flow injection and suction

The effect of flow injection and suction for reducing the flow separation inside an S-shaped inlet like used on some jet aircraft has been studied. To this aim computations and experimental measurements were performed of the flow in a M2129 type of duct tested at an inlet Mach number in the range 0.24-0.58. The experiments were used to validate the flow computations which would be a more flexible and convenient tool to explore and optimize different flow-control configurations. The grids generated for computation are suitable for detailed analysis of the baseline flows and of the effect of injection and suction. The computational results are substantially supported by the experimental measurements. The computations capture the fundamental characteristics of flow in the duct like the separation along the convex side of the bend and the crescent-shaped, high-pressure zone accompanied by a low-pressure bubble at the exit plane. Injection of 2% of the main flow before the first bend of the duct accompanied by suction of the same quantity past the second bend is an effective means to control the flow separation. Both the computations and the experiments show that with control the total-pressure distribution of the flow emerging from the duct is more axisymmetric and has higher overall value than in the uncontrolled cases. The results also suggest that a more uniform and symmetric distribution of the total pressure should be obtained by spreading the same control flow over a larger angle in the duct walls.