Received 26 July 2012, revised 24 April 2013, online published 19 July 2013 Defence Science Journal, Vol. 63, No. 4, July 2013, pp. 355-362, DOI : 10.14429/dsj.63.2545  2013, DESIDOC 1. INTRODUCTION Study of supersonic jets impinging on an inclined fat plate is important for scientifc investigation as well as practical applications. The problem of jet impingement in inclined plate for aerospace applications appears in the design of jet defector, multistage rocket separation at higher attitude, rocket test-stand environment, plume ducting system of canisterised missiles, space module attitude-control thruster operation, among others. Such fow feld contains many complex fuid dynamics phenomena like shock/shock interactions and shock/ boundary layer interactions. The jet structures change greatly depending on the inclined angle of the plate, jet pressure ratios and the nozzle-plate distance. It has been observed that under certain fow conditions, localized pressure peaks damaged the impingement plate. Inclined jet impingement exhibits more complex features than the perpendicular jet impingement 1,2 . The maximum pressure on the inclined plate can be several times larger than that on the perpendicular plate because of the complex shock-shock interactions. Moreover, the stagnation bubble may disappear when the plate angle decreases. Indeed, it is a great challenge to understand the physics of these fows and correctly predict the heat and pressure loads on the impinging plate. Most of the former studies on supersonic jet impingement deal with experimental investigation of perpendicular impingement on a fat plate 1-4 . These studies, explained the existence of stagnation bubbles that appears in the vicinity of the plate surface, affecting the pressure peaks on the plate surface and the stability of the jet. One of the earlier important works on supersonic jet impingement on inclined plate is the experimental study by Lamont and Hunt 5 . From the pressure measurement on the plate surface and shadowgraph visualization it has become clear that the plate inclination has a strong infuence on the pressure distribution. Kim and Chang 6 , and Wu 7,8 , et al. simulated numerically the experimental study of Lamout and Hunt by solving Euler and Navier Stokes equations respectively and obtained qualitative agreement with experimental results. These numerical studies could provide explanations of the complex shock interactions. Nakai 9,10 , et al. conducted an important experimental investigation of supersonic jet impingement on inclined plate with different inclination angles, pressure ratios and nozzle plate distances. They have measured detailed pressure distribution in the plate surface with pressure sensitive paints (PSP) and used Schlieren methods to visualize the fow feld. Based on the Schlieren images, different shock wave structures were classifed into three major types. According to this classifcation, the Type I fowfeld is mostly observed when the plate is nearly perpendicular to the jet, the nozzle-plate distance is large, and the pressure ratio is low. Three shock waves (upper tail shock in the upstream area, lower tail shock in the downstream area and bowl shaped plate shock in the middle area) appear over the plate in addition to the jet shock at the jet boundary. As the plate angle decreases (θ < 50°) the wall jet expands along the plate surface and generates an intermediate tail shock wave emanating from the triple point generated at the end of the plate shock wave and Type II fowfeld occurs. A convex plate shock region is formed where the plate shock and barrel shock interact in the upstream region and a ‘stagnation bubble’ region appears. As the plate angle decreases further (θ < 30°), the intermediate tail shock wave merges with the barrel shock wave and gives rise to Type III fow feld. Furthermore, Nakai 9 , Numerical Simulation of Supersonic Jet Impingement on Inclined Plate Malsur Dharavath and Debasis Chakraborty * Defence Research and Development Laboratory, Hyderabad – 500 058, India * E-mail: debasis_cfd@drdl.drdo.in ABSTRACT Supersonic jet impinging on an inclined plate is explored numerically by solving Reynolds Averaged Navier Stokes (RANS) equations using a commercial solver. The numerical uncertainty is quantifed by grid convergence index parameter analysis. Simulations capture crisply all the essential features of the fow feld including jet boundary, jet shock, upper tail shock, front and behind plate shocks. Good agreement between computational and experimental results for different plate angles forms the basis of further analysis. Four different two equations turbulence models predict similar jet structures. Effect of plate angles, pressure ratio, nozzle-plate distance on impinged jet structures are evaluated from numerical results. It has been observed that with increase in the plate angle, the maximum pressure zone in the plate changed from crescent shape to round shape. Well resolved RANS simulations are capable of capturing fner details of supersonic impinging jets on inclined plate. Keywords: Jet impingement, pressure ratio, computational fuid dynamics 355