Shock detachment from curved wedges by local choking: numerical verification

IF 1.7 4区 工程技术 Q3 MECHANICS
S. Mölder, A. Gulamhussein
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Abstract

Computational fluid dynamics shows that a shock wave can detach from the sharp leading edge of a curved wedge at a wedge angle smaller than the classical maximum flow deflection as well as the sonic wedge angle. This is attributed to the inability of the sonic flow, at the wedge trailing edge, to pass as much mass flow as is being admitted through the shock wave attached at the leading edge. At this condition, the flow is unsteady, causing both the sonic surface and the shock to make adjustments in their shapes and positions to achieve a steady state with mass-flow balance. As a result, the shock wave becomes detached. Time-accurate CFD calculations show the gasdynamic details of the adjustment where the flow and the detached shock assume a steady state as the mass-flow imbalance gradually decreases to zero. This mechanism of shock detachment, occurring near the leading edge, is called local choking to distinguish it from shock detachment due to global choking that occurs because of flow choking at the exit of a convergent duct and to distinguish it as well from detachment due to an excessive leading-edge deflection. The local choking mechanism has been postulated to be a cause of shock detachment from doubly curved wedges. An analysis, based on curved shock theory and confirmed by CFD, shows that local choking and shock detachment from a doubly curved leading edge are dependent on Mach number, wedge angle, wedge curvature (both streamwise and cross-stream), and wedge length.

Abstract Image

由局部窒息引起的弯曲楔的激波脱离:数值验证
计算流体力学表明,激波可以在小于经典最大流动偏转角和声速楔角的楔形尖角处脱离弯曲楔。这是由于楔形尾缘处的声波流无法通过前缘处的激波所允许的质量流。在这种情况下,流动是非定常的,使得声面和激波都进行形状和位置的调整,从而达到质量流量平衡的稳态。结果,冲击波被分离了。时间精确的CFD计算显示了调整的气体动力学细节,其中随着质量流量不平衡逐渐减小到零,流动和分离激波呈现稳定状态。这种发生在前缘附近的激波脱离机制被称为局部窒息,以区别于由于汇聚管道出口处的流动窒息而导致的全局窒息所导致的激波脱离,也区别于由于前缘过度偏转而导致的脱离。局部窒息机制被认为是双弯曲楔的激波脱离的原因。基于弯曲激波理论并经CFD验证的分析表明,双弯曲前缘的局部窒息和激波脱离与马赫数、楔形角、楔形曲率(包括顺流和横流)和楔形长度有关。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Shock Waves
Shock Waves 物理-力学
CiteScore
4.10
自引率
9.10%
发文量
41
审稿时长
17.4 months
期刊介绍: Shock Waves provides a forum for presenting and discussing new results in all fields where shock and detonation phenomena play a role. The journal addresses physicists, engineers and applied mathematicians working on theoretical, experimental or numerical issues, including diagnostics and flow visualization. The research fields considered include, but are not limited to, aero- and gas dynamics, acoustics, physical chemistry, condensed matter and plasmas, with applications encompassing materials sciences, space sciences, geosciences, life sciences and medicine. Of particular interest are contributions which provide insights into fundamental aspects of the techniques that are relevant to more than one specific research community. The journal publishes scholarly research papers, invited review articles and short notes, as well as comments on papers already published in this journal. Occasionally concise meeting reports of interest to the Shock Waves community are published.
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