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Drag reduction of supersonic blunt bodies using opposing jet and nozzle geometric variations

机译：利用相反的射流和喷嘴几何变化降低超音速钝体的阻力

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Passive and active flow control methods are used to manipulate flow fields to reduce acoustic signature, aerodynamic drag and heating experienced by blunt bodies flying at supersonic and hypersonic speeds. This paper investigate the use of active opposing jet concept in combination with geometric variations of the opposing jet nozzle to alleviate high wave drag formation. A numerical study is conducted to observe the effects of simple jet as well as jet emanating from a divergent nozzle located at the nose of a blunt hemispherical body. An initial discussion is presented of the complex shock wave pattern flow physics occurring when opposing jet ejected from a nozzle under various operating conditions interacts with the free stream flow. The complex flow physics that include long penetration and short penetration mode is studied in conjunction with effect on drag. The numerical setup consists of supersonic free stream flow interacting with an opposing sonic jet under varying pressure ratios. Initial computational results are validated by identifying prominent flow features as well as comparing available experimental data of surface pressure distributions. Preliminary validation is followed by the introduction of a divergent nozzle in the blunt body nose region. A series of numerical iterations are performed by varying nozzle geometric parameters that include nozzle divergent angle and nozzle length for a certain jet pressure ratio. Long penetration mode, short penetration mode as well as flow separations are captured accurately during the analysis. The results show a considerable reduction in drag by the use of a divergent nozzle. Specifically, 46% and 56% reduction in drag coefficient is achieved at pressure ratio of 0.6 and 0.8 respectively in the divergent nozzle cases as compared to the simple blunt body without any nozzle. (C) 2017 Elsevier Masson SAS. All rights reserved.
机译：被动和主动流控制方法用于操纵流场，以减少以超音速和高音速飞行的钝体所经历的声学特征，空气阻力和发热。本文研究了主动对流射流概念与对流射流喷嘴的几何变化的组合，以减轻高波浪阻力的形成。进行了数值研究，以观察简单射流以及从钝半球体鼻子处的发散喷嘴射出的射流的影响。初步讨论了在各种操作条件下从喷嘴喷射的反向射流与自由流相互作用时发生的复杂冲击波模式流物理学。结合长阻力和短阻力模式研究了复杂的流动物理学。数值设置由超音速自由流与变化压力比下的相对音速射流相互作用组成。通过识别突出的流动特征以及比较表面压力分布的可用实验数据，可以验证初始计算结果。初步验证之后，在钝头的鼻子区域引入了发散喷嘴。通过改变喷嘴几何参数来执行一系列的数值迭代，这些参数包括对于特定喷射压力比的喷嘴发散角和喷嘴长度。在分析过程中，可以准确捕获长渗透模式，短渗透模式以及流分离。结果表明，通过使用发散喷嘴可以显着降低阻力。具体地说，与没有任何喷嘴的简单钝体相比，在发散喷嘴情况下，在压力比为0.6和0.8时，阻力系数分别降低了46％和56％。 （C）2017 Elsevier Masson SAS。版权所有。

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