Nozzle Flow Influence on Forebody Aerodynamics
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ORIGINAL PAPER
Nozzle Flow Influence on Forebody Aerodynamics Sangha Park1 · Gisu Park1 · Soo Hyung Park2 Received: 27 November 2019 / Revised: 17 February 2020 / Accepted: 19 March 2020 © The Korean Society for Aeronautical & Space Sciences 2020
Abstract In this study, the nozzle flow influence on the forebody aerodynamics has been numerically investigated and validated with experiment. To understand the nozzle flow aerodynamics on the forebody, five different nozzle-exit profiles, which are often encountered in the experiments, are considered one at a time. One flow condition is considered at a nominal freestream Mach number of 4. The CFD simulations are performed using a two-dimensional axisymmetric four-equation transition shear stress transport (SST) turbulence model. The numerical results are compared with the Ludwieg tube Mach 4 experimental data and showed good agreement. The numerical results showed that despite the slight effect on the wall static pressure depending on the nozzle profiles considered, the physical flow phenomena such as shock shape are directly influenced. With the undeveloped nozzle flow profile case, however, significant pressure differences are observed. The distance between the model and the nozzle exit may significantly affect the forebody aerodynamic characteristics, and so, the consideration of the distance between the model and nozzle exit needs to be placed during the model setup to reduce the unwanted uncertainty in the measurement. Keywords Nozzle flow · Ludwieg tube · Forebody · Aerodynamics
1 Introduction In wind tunnel facilities, flow uniformity is the primary concern to measure the properties of the test models accurately. For decades, numerous studies have been performed both experimentally and numerically to investigate the uniformity of a supersonic/hypersonic nozzle flow. The non-uniform flow generated from a nozzle could become an issue in replicating a desired environmental flow condition. To maintain uniform nozzle-exit flows, despite the sophisticated design and expensive manufacturing cost, the usage of a contour nozzle is in general recommended against that of a conical nozzle. The recommendation of contour nozzle usage is stemmed from that the measurement performance of a hypersonic facility may depend on the uniform freestream quality of the nozzle-exit flow [1].
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Gisu Park [email protected]
1
Department of Aerospace Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
2
Department of Aerospace Information Engineering, Konkuk University, Seoul 05029, Republic of Korea
In supersonic/hypersonic wind tunnel facilities, a converging–diverging nozzle is commonly used to generate a high-speed flow in the test section. The relatively small-size test section compared to the subsonic facility is one characteristic of a hypersonic wind tunnel. The characteristic of the small size of the test section in a wind tunnel is likely to increase the noise level in the freestream [2]. In a nozzle-exit freestream flow, the no
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