Effect of Vortex Generator on Flow in a Serpentine Air Intake Duct

Abstract

AbstractLow Radar Cross Section (RCS) is one of the important requirements of aircraft design for stealth. Rotating engine face components are one of the major sources of radar reflection and hence need special attention. To this end, present day aircraft air intake ducts are designed to hide the rotating components from the radar signal by incorporating multiple bends. This type of intake ducts ensures that there is no direct line of sight from the entrance of the duct to engine face components and are generally called as Serpentine Ducts. Design of serpentine duct, therefore involves sharp bends that are likely to cause flow separation and consequent instability and distortion in the flow. In order to realize optimal performance from the engine, it is necessary to reduce the losses and minimize distortion at the Aerodynamic Interface Plane (AIP) that is near the outlet of the duct. This requires use of flow control techniques to alleviate the effects of flow separation. A Serpentine duct described in (Hamstra et al. in Active inlet flow control technology demonstration. ICAS, 2000 [1]) was selected for the present study, as the geometry details and experimental results were reported in the paper. Based on this, a duct was created and CFD flow simulations were performed. Results so obtained were compared with the test results in order to establish a baseline duct. Subsequently, passive vortex generators of trapezoidal shape were introduced and CFD simulations were carried out. The results, in comparison with the base design, indicate an enhancement in the flow uniformity at the AIP although with a 3% reduction in the pressure recovery. Further course of study is also indicated.KeywordsSerpentine intake ductTrapezoidal vortex generatorPassive flow control