International Journal of Universal Science and Engineering http://www.ijuse.in (IJUSE) 2021, Vol. No. 7, Jan-Dec e-ISSN: 2454-759X, p-ISSN: 2454-7581 19 Presented at International Conference on Innovations in Multidisciplinary Research (ICIMR-2021) Held on 23 rd & 24 th August, 2021 STUDY OVER DIFFERENT NOZZLE PROFILES FOR NOZZLE FLOW SEPARATION CONTROLS *Gundam Venkata Harsha Vardhan Reddy, *Gubba Rakesh, ** Jainul Abedin, ** Ashutosh kumar *Department of Mechanical Engineering, Sreenidhi Institute of Science and Technology, Telangana-501301, India. **Department of Research and Development, Abyom Space tech and Defence Pvt. Ltd, Gorahkpur-274402, India. ABSTRACT Since the dawn of the space age, flow separation issue in rocket nozzles has been an unwanted phenomenon for the engineers. So, naturally, this became a task for the engineers which is to be brought under control. But it turned out to be a daunting task; even though many were able to explain the physics behind this phenomenon, it is not fully understood even to the present day. So, there are not many methods, which explains how to control or suppress this phenomenon. This paper aims to study about two of those few methods which affectively are able to suppress flow separation in rocket nozzles. Keywords- Flow separation, FSS, RSS, Nozzles INTRODUCTION The nozzle is the main part of the rocket, which provides the required exhaust flow to propel the rocket into space with supersonic speeds. Up to this date, different types of profiles are used based on the different requirements and applications. But all these nozzles are based upon the de-Laval nozzle; de Laval nozzle consists of a convergent section, a throat, and a divergent section. Rocket nozzle profiles can be classified as follows; conical, Truncated Ideal Contoured (TIC), Thrust Optimized Contoured (TOC), and Thrust Optimized Parabolic bell (TOP), Compressed Truncated perfect (CTP) nozzles. Even though these nozzles are being used since the dawn of the space age, there is a concept of nozzle flow that is not fully understood to the present day, which is nozzle flow separation. Nozzle flow separation occurs when the boundary layer gets separated from the nozzle wall; this phenomenon is quite undesirable. When exit pressure of nozzle is in the range of 0.4 to 0.8 of local atmospheric pressure [3], ambient air tries to enter into the viscous layer. Thus, due to the adverse pressure gradient, the boundary layer will get separated from the wall. In general, overexpanded nozzles are used to obtain optimum nozzle flow pattern, which helps to attain maximum thrust at the desired altitude. But these overexpanded nozzles experience nozzle flow separation. The nozzle flow separation patterns vary which operating pressure, nozzle profile, exhaust gas properties, back pressure, etc. The nozzle flow separation patterns can be classified as follows; Free Shock Separation (FSS) and Restricted Shock Separation (RSS) [1]. Both these flow separation phenomena and then modes to suppress the RSS phenomena are discussed in detail. LITERATURE REVIEW Most of the works which study nozzle flow separation, concludes that the ambient pressure is the main reason why flow separation occurs. The presence of adverse pressure gradients causes the