Indian Conference on Applied Mechanics (INCAM) 2013 IIT Madras, 4 – 6 July 2013 Page 1 of 9 INVESTIGATION OF FLOW CONTROL IN TRANSITION AIR-INTAKE USING SYNTHETIC JET ACTUATOR Nithin Hegde  Prakhar Kant Tiwari  , Akshoy Ranjan Paul † and Anuj Jain *Postgraduate Student, Department of Applied Mechanics  Undergraduate Student, Department of Mechanical Engineering †Assistent Professor, Department of Applied Mechanics Professor, Department of Applied Mechanics Motilal Nehru National Institute of Technology Allahabad, Allahabad- 211 004, Uttar Pradesh, India. Presenting author’s email: nithinbhegde@gmail.com, prakharpkt@gmail.com Abstract Present study proposes the application of zero net mass flux actuator or synthetic jet actuator to control the flow in twin transition 20 centerline curvature air-intakes at Reynolds Number = 1.0310 5 . Due to curvature and diffusion commonly cause flow separation and associated total pressure losses within serpentine intakes. This causes distortion and total pressure losses at intake exit with low static pressure recovery. SJA found effectively controls the separation at inner wall of intake. Static Recovery coefficient at exit plane of air-intake is increases and Total pressure loss coefficient continuously decreases as velocity ratio increase as compared to uncontrolled case. With using SJA it has been noted that 6.64% increment of CSP at VR=4.0 as compared to uncontrolled baseline air-intake. SJA at velocity ratio between 2.0 to 4.0 distortion coefficient decreases 64.49% with respect to uncontrolled case. As the velocity ratio increases beyond 4.0 the distortion in the flow increases and also noted the decrement of secondary velocity with the use of flow control. The total pressure which refers to the total energy contained in the fluid hence improve in total pressure loss coefficient is observed. Keywords: Synthetic jet actuator, Transition diffuser, Computational fluid dynamics, turbulent model, Velocity ratio. 1. Introduction The propulsion system of the next generation of aircraft will be designed for higher efficiency and durability. Air intake is crucial part of propulsion system of an aircraft, which ensures the supplies of mass flow demand of the engine over a range of aircraft speeds and altitudes with high pressure recovery and at minimum flow distortion. For many military applications the inlet geometry is important for stealth requirement. A serpentine inlet can be used to hide the line of sight to the compressor face in order to reduce the infra-red signature [1]. Most of single engine military aircrafts carries Y-shaped twin air-intake duct, which is mounted on either sides of the fuselage and carries atmospheric air in to the compressor. Due to space constraint, the diffusers need to be curved, which causes severe flow non- uniformity at the engine face and separation on the curved surface causes flow distortion. The distortion causes premature engine surge and flow non-uniformity which may cause range of undesirable effects including asymmetric loading of the compressor blades. The design of engine inlets is one area where the prevention of flow separation may be significant in improving the over-all efficiency of the vehicle [2]. Separation control methods have been classified as active or passive, depending on whether control involves energy expenditure or not [3]. Active flow control is one of the leading areas of research of many scientists and engineers in fluid mechanics. A synthetic jet actuator, as shown in Fig 1 consists of a small cavity with a vibrating diaphragm at its bottom side and an orifice plate at the opposite side. During a downward motion of the diaphragm the surrounding air is drawn into the cavity. When the diaphragm is moving upward, the fluid in the cavity is expelled through the orifice producing a vortex ring at the exit of the orifice. Repeating this process at a certain frequency produces a succession of vortices