2018年5月23日学术报告:激波-涡环相互作用不稳定性的谱研究

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报告题目:激波-涡环相互作用不稳定性的谱研究

TopicSpectrum Study on Unsteadiness of Shock wave - Vortex Ring Interaction

报告人:刘超群教授,德州大学阿灵顿分校

Speaker: Prof.Chaoqun Liu,  University of Texas at Arlington

 

主持人:詹杰民教授

Chair: Prof.Jiemin Zhan

时间:2018523日(星期三)下午15:00

Time: Wednesday, 23th.May,2018, 15:00pm

地点:东校园工学院B403讲学厅

Venue: Room B403, School of Engineering, East Campus, SYSU

 

欢迎广大师生踊跃参加!

 

报告摘要超声速流动中常见的低频不稳定激波振荡现象,是激波与边界层相互作用引起的流动分离控制研究的首要任务。采用隐式大涡模拟(ILES)方法,模拟了微型涡流发生器(MVG)Ma=2.5超声速流压缩拐角激波与涡环的相互作用。并对涡环运动和激波振荡进行了压力频率和密度的观察和分析。结果表明,压缩拐角激波的无量纲低频主频ST=0.002,而MVG后面的涡环的高频主频ST=0.038。激波的低频主频是有害的,可以利用激波与涡环的相互作用,通过主频高频的涡环来消除或减弱。在激波与涡环的相互作用区域,出现了主频ST=0.037~0.038,而不是低频主频ST=0.002,这表明涡旋环的刚度足以破坏或减弱激波。该分析利用激波与涡环的相互作用,通过优化高频涡的产生,为消除或削弱对飞行器结构和环境保护都有很大危害的500 HZ以下低频压力脉动提供了有力的工具。

 

Abstract: Shock oscillation with low-frequency unsteadiness is commonly observed in supersonic flows and is a top priority for control of flow separation caused by shock wave and boundary layer interaction or SWBLI.In this paper, the interaction of the shock caused by the compression ramp and the vortex rings generated by a micro vortex generator (MVG) in a supersonic flow at Ma = 2.5 is simulated by the Implicit Large Eddy Simulation (ILES) method. The observation and analysis on the frequency of pressure and density are carried out on both the vortex ring motion and the shock oscillation. The results show that the shock produced by a compression ramp flow at Ma = 2.5 has a dominant non-dimensional low frequency which is around St = 0.002, while the vortex rings behind the MVG have a dominant high frequency which is around St = 0.038. The dominant low frequency of the shock, which is harmful, can be removed or weakened through the shock-vortex ring interaction by the vortex rings which generate high frequencies fluctuation. In the shock and vortex ring interaction region, a dominant high frequency St = 0.037~0.038 has been detected, rather than the low frequency St = 0.002, which indicates that the vortex ring is stiff enough to break or weaken the shock. This analysis could provide a very powerful tool to remove or weaken the low frequency pressure fluctuation below 500 HZ, which is very harmful to flight vehicle structure and environmental protection, by optimization of high frequency vortex generation and through the shock-vortex interaction.

 

 

刘超群教授简介:

刘超群博士,德州大学阿灵顿分校数学系教授。1967年及1981年毕业于清华大学并获得学士学位(流体力学)、硕士学位(计算流体力学),1989年毕业于科罗拉多大学丹佛分校获博士学位(应用数学)。承担项目超过50项,经费超过500万美元,发表论文超过200篇,目前研究兴趣集中在Numerical Analysis Multigrid Multilevel Adaptive Methods Computational Fluid Dynamics Direct Numerical Simulation Large Eddy Simulation High-order Numerical Scheme Numerical Combustion Software Development 等。