International Journal of Recent Technology and Engineering (IJRTE) ISSN: 2277-3878, Volume-8 Issue-2S8, August 2019 1769 Published By: Blue Eyes Intelligence Engineering & Sciences Publication Retrieval Number: B11500882S819/2019©BEIESP DOI:10.35940/ijrte.B1150.0882S819 ABSTRACT---This present study discusses the outcome of the experimental investigations, and the efficacy of the tiny jets used to regulate the base pressure as well as the wall pressure in suddenly expanded flow. The control mechanism as tiny jets having a cross-section of 1 mm diameter was employed as the base pressure regulator at the exit periphery of the nozzle. The experiments were carried out to investigate and record the flow field at the rear end of the separated flow region for area ratio 4.84. Four tiny jets were placed at a distance of 6.5 mm away from the primary jet coming from the nozzle exit at ninety degrees apart, and the tiny control jets were flowing at sonic Mach number. The actual Mach number of the main jet was 1.1. The experimentation was accomplished at a different level of expansion (i. e., NPR = 3, 5, 7, 9, and 11) and the L/D ratio considered was from 10 to 1. This study mainly focuses on the development of the flow in the suddenly expanded duct, nature of the flow in the duct, and the impact of the Control on the wall pressure and the magnitude of the pressure along the duct. The wall pressure in the smooth duct is not unfavorably influenced by the control jets. Keywords—CD Nozzle, Microjet, Wall Pressure, and Mach number. I. INTRODUCTION Investigators in the area of external dynamics have long been wondering about the low pressure and the flow separation at the blunt base or at the backward-facing step. At the blunt base, when the flow separates the flow is divided into two regions. One is the separated zone, which separates it from the main jet, and the other is being the wake region or the recirculation corner flow. The pressure in the wake/separated region will be less than the ambient pressure, which results in the drag penalty in the case of external aerodynamics. This penalty in terms of the base drag is substantial at the transonic Mach numbers. Once, the flow is reattached with the duct wall, from the reattachment point again; the boundary layer will grow. While scanning the literature, it is observed that at transonic speed, the contribution of the base drag is significant due to the low pressure/sub-atmospheric pressure at the base corner. This may account for around seventy percent of the net value of the drag. The researcher also tried to optimize the skin friction drag as well as the wave drag, Revised Manuscript Received on August 19, 2019. Mohammed Faheem, Dept. of Mechanical Engineering, Faculty of Engineering, International Islamic University, Kuala Lumpur, Malaysia Mohammed Kareemullah,Dept. of Mechanical Engineering P. A. College of Engineering, Nadupadav, Kairangala, Mangalore. Abdul Aabid,Dept. of Mechanical Engineering, Faculty of Engineering, International Islamic University, Kuala Lumpur, Malaysia. Imran Mokashi,Dept. of Mechanical Engineering, Faculty of Engineering, International Islamic University, Kuala Lumpur, Malaysia. S. A. Khan, Dept. of Mechanical Engineering, Faculty of Engineering, International Islamic University, Kuala Lumpur, Malaysia, (sakhan@iium.edu.my) but there is no more scope to reduce the drag. Skin friction will be there by virtue of the wetted surface area of the aerodynamic vehicles, and we do not have any control as there is a requirement from the end-user of the space department. Further, the wave drag is bound to be present due to the formation of the shock waves at the nose portion of the projectiles/missiles/shells at supersonic Mach numbers. However, the wave drag will be least if the nose fineness ratio is between 2.5 to 4. In view of the above situation, the researchers in the field of external ballistics are mostly concentrating on controlling the base pressure, which is a significant concern. Another primary concern and aspect while studying the base flows are whether to study by internal flow techniques or the external flow techniques. If we decide and opt to use the external flow methods for our investigations, then there are so many problems which are associated with the external flow study. One of them is the requirement of abundant air supply and to do that we need heavy-duty compressor which will consume enormous electrical power at the same time there is a requirement of larges storage tanks to store the air. In the present scenario, there is an acute shortage of energy. Hence, we need to look for other alternative methods which will result in energy savings in view of the depletion of the energy sources, and especially the fossil fuels which are likely to get exhausted in few years. Since the study of the flow field around the aerodynamic bodies by means of the external aerodynamics is not feasible due to the cost involved in it, another significant disadvantage of external aerodynamics is that due to the presence of support mechanism it will cause a lot of errors in the measured data. The support mechanism and sting will introduce the errors in the measurements. Another problem with the external aerodynamics is how to avoid the influence of the boundary layer in the test section. In this study, we opted for internal flow methods to study the base pressure flow field. It is well known that for lower Mach number the disturbances created will propagate all along in the circular waveform. But when Mach number is unity, there will be a normal shock wave, and the entire area is vertically divided into two halves. Once the flow Mach number is more than unity an oblique shock will be formed at the nose of the shell/missile/rocket/bomb which will further reduce the zone of action and zone of silence will be around seventy-five percent. Hence, we can state that the internal and external flow is principally the same. In the case of external flow, the flow Experiment on of Nozzle Flow with Sudden Expansion at Mach 1.1 Mohammed Faheem, Mohammed Kareemullah, Abdul Aabid, Imran Mokashi, S. A. Khan