Shock-free compressible vortex rings impinging on a stationary surface: Effects of surface angle variation
Shock-free compressible vortex rings impinging on a stationary surface: Effects of surface angle variation
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DOI：
10.1016/j.expthermflusci.2013.01.008
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发表时间：
2013-05
影响因子：
3.2
通讯作者：
R. Mariani;M. K. Quinn;K. Kontis;L. Marraffa
中科院分区：
文献类型：
--
作者：
R. Mariani;M. K. Quinn;K. Kontis;L. Marraffa
对可压缩涡旋环在静止、倾斜、光滑表面上的撞击进行了实验研究。评估了四种表面角度倾角：90°（垂直于流纵轴）、75°、60°和45°。在90°基准情况下，假定流动是轴对称的。使用单一压力比为~ 4，对应于实验入射激波马赫数为~ 1.31，产生无激波可压缩涡环。结果表明：激波与接近的旋涡结构的相互作用和旋涡环对表面的撞击是两个主要的流动过程。在表面倾角大于90°时，这些过程是不对称的，反射激波的形状被接近的涡流环改变。反射激波的下外段最初被涡环的下核衍射，其中央部分随后被环面中央部分捕获，最终上外段被上核衍射。旋涡环随后撞击地表，下核先撞击，发生不对称拉伸和变形。流场研究表明，当流动从对称撞击向非对称撞击转变时，速度大小和涡度场会出现初始减小，这可能是由于边界层的不均匀形成所致。由于气流向上偏转，上堆芯的速度大小和涡度场随之再次增大。相反，较低的核心被视为消散。表面压力测量证实了流动发展的不对称性。随着表面角度的变化，中心测量位置的压力随着驻点位置的改变而降低。在表面测量的一个有趣的特征是一个强大的横向加速度，由于涡旋线的形成，在主涡旋核心周围滚动。
An experimental study has been conducted on the impingement of compressible vortex rings on stationary, inclined, smooth surfaces. Four surface angle inclinations were evaluated: 90° (perpendicular to the flow longitudinal axis), 75°, 60°, and 45°. The flow was assumed axisymmetric for the 90° benchmark case. A single pressure ratio of ∼4 was used, corresponding to an experimental incident shock wave Mach number of ∼1.31, generating a shock-free compressible vortex ring. Results showed two main flow processes: the interaction of the reflected shock wave with the approaching vortical structure, and the impingement of the vortex ring on the surface. At surface inclination angles other than 90°, these processes are asymmetrical and the shape of the reflected shock is modified by the approaching vortex ring. The lower outer section of the reflected shock wave is initially diffracted by the lower core of the vortex ring, its central section is then captured by the central section of the torus, and ultimately the upper outer section is diffracted by the upper core. The vortex ring subsequently impinges on the surface with the lower core impacting first, undergoing an asymmetrical stretching and deformation. Flow field studies showed an initial decrease in velocity magnitude and vorticity field as the flow transitioned from a symmetrical to an asymmetrical impingement, possibly due to the uneven formation of the boundary layer. The velocity magnitude and vorticity field of the upper core subsequently increase again, as a result of the upwards deflection of the flow. Oppositely, the lower core is seen to dissipate. Surface pressure measurements confirmed the asymmetry in the flow development. As the surface angle is varied, the pressure at the central measurement location is seen to decrease as the position of the stagnation point is altered. An interesting feature within the surface measurements is a strong lateral acceleration due to the formation of vortex lines which roll around the main vortex core.