Studies on Suddenly Expanded Flow at Different （突然扩大的研究在不同的流动）.pdf

International Journal of Scientific Engineering Research, Volume 3, Issue 8, August-2012 1 ISSN 2229-5518 A Study on Suddenly Expanded Flow at Different Levels of Over Expansion for Area Ratio 3.24 M. Ahmed Ali Baig, Sher Afghan Khan Abstract- The experimental investigations carried out to study the variations in base pressure at different levels of over expansion of jet in a suddenly expanded axi-symmetric duct is presented in this paper. The two different fixed levels of Over Expansion select ed in the study are 0.277 and 0.56. The area ratio of the present study is 3.24. The jet Mach numbers at the entry to the suddenly expanded d uct, studied are 2.2 and 2.58. The length-to-diameter ratio of the suddenly expanded duct is varied from 10 to 1. Active control in the form of four micro 0 jets of 1mm orifice diameter located at 90 intervals along a pitch circle diameter of 1.3 times the nozzle exit diameter in the base region are employed. In addition to base pressure, wall pressure field along the duct is also studied. From the present studies it is found that at a high level of over expansion micro jets are marginally effective. It is also found from wall pressure studies that the micro jets do not disturb the flow field in the enlarged duct. Index Terms-Active Control, Over expanded jet, Wall pressure distribution, Base Pressure 1. INTRODUCTION The sudden expansion of flow in both subsonic and supersonic regimes of flow is an important problem with a wide range of applications. The use of a jet and a shroud configuration in the form of a supersonic parallel diffiuser is an excellent application of sudden expansion problems. Another interesting application is found in