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Subject: search.filters.subject.Supersonic flow

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    Parametric study on wing-lambda-shock formation
    (2021-01-01)
    Chainok, Sirikorn
    ;
    Rungroch, Thanapol
    ;
    Chairach, Pattarasuda
    ;
    Prapamonthon, Prasert
    ;
    Yooyen, Soemsak
    It is well-known that a wing is one of the most important parts of an aircraft as it is used to generate lift force. According to a wing moving at sufficiently high subsonic speeds, the flow speed on the wing's upper surface can be supersonic due to acceleration through the curvature-created suction, thereby forming a shock wave in a lambda shape. Additionally, the lambda shock can interact with the boundary layer flow. These phenomena relate to disturbances in the flow field, including flow separation, thus causing undesirable effects on lift production. Hence, a better understanding of the phenomenon of wing-lambda-shock formation and its nature is essential. This study presents a numerical investigation of the lambda-shock formation on an ONERA M6 wing, which is known as a swept, semi-span wing with no twist, under parametric effects of angleof-attack, and free-stream Mach number, which is increased up to the supersonic regime. The pressure coefficients obtained by simulations are validated by open data. Then, numerical results in terms of the local pressure coefficient, local Mach number, averaged lift and drag coefficients, and?-shape characteristics based on Mach number and pressure coefficients are discussed under an investigated range of the parameters. Results show that the angle-of-attack and free-stream Mach number can affect the lambda shock formation on the wing upper surface physically. Specifically, an iso-sonic surface with lambda shock waves is disturbed when the angle-of-attack and free-stream Mach number vary in an investigated range. This also affects lift and drag coefficients of the wing.
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    Multi-objective design optimization of the combinational configuration of the upstream energy deposition and opposing jet for drag reduction in supersonic flows
    (2020-10-01)
    Ju, Shengjun
    ;
    Sun, Zhenxu
    ;
    Yang, Guowei
    ;
    Prapamonthon, Prasert
    ;
    Zhang, Junyuan
    Optimization design has been widely used in the supersonic vehicle design process and the drag reduction characteristic is an important objective of the optimization. The drag reduction mechanism applied to the blunt body with the combinational configuration of the upstream energy deposition and opposing jet for drag reduction has been conducted numerically. In the current study, the three-dimensional coupled implicit compressible Reynolds Averaged Navier-Stokes equations and Menter's shear stress transport turbulence model are employed to simulate the flow fields around the blunt body with the combined method. The results show that in the jet-to-freestream total-pressure ratio of 0.2 and 0.4, the drag is reduced by 47.44% and 45.96%, respectively. Further, the Latin hypercube method is used for the generation of initial samples for optimization and the multi-objective design optimization algorithm coupled with the Kriging model surrogate model is applied to determine optimal flow control parameters. The drag reduction factor R<inf>d</inf> and drag reduction effectiveness E<inf>eff</inf> are selected as optimization objectives. The Pareto-optimal front for the multi-objective design optimization results is acquired and there exists a challenging tradeoff between the two optimization objectives. The drag reduction factor R<inf>d</inf> and drag reduction effectiveness E<inf>eff</inf> further increase as much as 28.16% and 116.47%, respectively. The jet has a stronger penetration in the optimum design condition, and the findings suggest that the strategy of adding energy spot to the upstream flow field of the opposing jet can be an effective way for drag reduction.
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    Parametric study on drag reduction with the combination of the upstream energy deposition and the opposing jet configuration in supersonic flows
    (2020-06-01)
    Ju, Shengjun
    ;
    Sun, Zhenxu
    ;
    Yang, Guowei
    ;
    Prapamonthon, Prasert
    ;
    Zhang, Junyuan
    The drag reduction characteristics play an important role in the supersonic vehicle design phase. According to two drag reduction schemes, the opposing jet and the upstream energy deposition have aroused the widespread interest of researchers. In the current study, the drag reduction effectiveness of a blunt body with the combination of the upstream energy deposition and the opposing jet configuration in supersonic flows is investigated numerically. The three-dimensional coupled implicit compressible Reynolds Averaged Navier-Stokes (RANS) equations coupled with the Menter's shear stress transport (SST) turbulence model are applied to numerically predict flow fields of the blunt body, the variance analysis method is introduced to a parametric study on the drag reduction. Results indicate that a larger overall drag is decreased by the combinational configuration than the single strategies of the opposing jet and the energy deposition. The proposal of the combination of the upstream energy deposition and the opposing jet configuration can be used as an effective method of drag reduction. Meanwhile, due to the existence of the upstream energy deposition, the stability and penetrability of the opposing jet substantially increase, especially for the long penetration mode. Further, some recommendations are provided for the drag reduction factor and drag reduction effectiveness.