Influence of nozzle geometry on the near-field structure of a highly underexpanded sonic jet |
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| Institution: | 1. Kitakyushu National College of Technology, Kitakyushu 802-0985, Japan;2. Saga University, Saga 840-8502, Japan;3. Andong National University, Andong, Korea;1. School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798, Singapore;2. School of Aerospace Engineering, Huazhong University of Science and Technology, 1037 Luoyu East Road, 430074, China;1. Department of Mechanical and Manufacturing Engineering, Schulich School of Engineering, University of Calgary, Calgary, Alberta, Canada;2. Faculty of Mechanical Engineering, Semnan University, Semnan, Iran;3. Fuel and Combustion Development Department, Irankhodro Powertrain Co., Tehran, Iran;4. Department of Mechanical Engineering, K. N. Toosi University of Technology, Tehran, Iran;1. Graduate School of Hanyang University, Seoul, Republic of Korea;2. Department of Mechanical Engineering, Hanyang University, Seoul, Republic of Korea;1. RMIT University, School of Aerospace, Mechanical and Manufacturing Engineering, Melbourne 3000, Australia;2. RMIT University, School of Media and Communication, Melbourne, Australia;3. Volvo Car Corporation, Göteborg, Sweden |
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| Abstract: | Detailed near-field structures of highly underexpanded sonic free jets have been investigated with the help of computational fluid dynamics. Two-dimensional, axisymmetric Euler equations have been chosen to predict the underexpanded jets, and the third-order total variation diminishing finite-difference scheme has been applied to solve the system of governing equations numerically. Several different nozzles have been employed to investigate the influence of the nozzle geometry on the near-field structures of highly underexpanded sonic free jets. The results obtained show that the distance from the nozzle exit to the Mach disk is an increasing function of the jet–pressure ratio, which also significantly influences the shape of the jet boundary. The diameter of the Mach disk increases with the jet–pressure ratio, and it is further significantly influenced by the nozzle geometry, unlike the distance of the Mach disk from the nozzle exit. However, such a dependence on the nozzle geometry is no longer found when an effective-diameter concept is taken into account for the flow from a sharp-edged orifice. A good correlation in the diameters of the Mach disk is obtained, so that the near-field structure of highly underexpanded sonic free jets is a unique function of the pressure ratio, regardless of the nozzle geometry. |
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