论文标题
通过次级斜压在冲击相互作用中通过次级斜压涡度混合的增强
On mixing enhancement by secondary baroclinic vorticity in shock-bubble interaction
论文作者
论文摘要
为了研究通过可变密度行为混合增强的固有机制，经过数值研究并与被动标量（PS）混合的对应物进行比较。观察到，VD SBI中最大浓度衰减的速度要比PS SBI中的衰减速度快得多，而不论电击马赫数如何（MA = 1.22〜4）。通过分析延伸气泡的方位速度，可以找到PS SBI中的准长摩纱型速度分布。同时，对于VD SBI，次级斜压涡度（SBV）产生增强了另外的拉伸，这会导致更快的混合衰变。 SBV增强拉伸的潜在机制通过冲击的光气泡和重型环境空气之间的密度和速度差异进一步揭示。通过将SBV加速拉伸模型和初始冲击压缩组合，理论上是通过在轴对称涡流的变形场下与其他SBV诱导的azimuthal速度求解的反式扩散方程来提出的新颖的VD SBI混合时间估计。基于混合时间模型，由VD和PS混合时间比例定义的混合增强数进一步揭示了可变密度效应的贡献，这意味着可以更好地控制密度分布以在超音速流涡流中混合增强。
To investigate the intrinsic mechanism for mixing enhancement by variable density behaviour, a canonical variable density (VD) mixing extracted from a supersonic streamwise vortex protocol, shock bubble interaction (SBI), is numerically studied and compared with a counterpart of passive scalar (PS) mixing. It is meaningful to observe that the maximum concentration decays much faster in VD SBI than in PS SBI regardless of the shock Mach number (Ma = 1.22 ~ 4). The quasi-Lamb-Oseen type velocity distribution in the PS SBI is found by analyzing the azimuthal velocity that stretches the bubble. Meanwhile, for the VD SBI, an additional stretching enhanced by the secondary baroclinic vorticity (SBV) production contributes to the faster-mixing decay. The underlying mechanism of the SBV-enhanced stretching is further revealed through the density and velocity difference between the shocked light bubble and the heavy ambient air. By combining the SBV-accelerated stretching model and the initial shock compression, a novel mixing time estimation for VD SBI is theoretically proposed by solving the advection-diffusion equation under a deformation field of an axisymmetric vortex with the additional SBV induced azimuthal velocity. Based on the mixing time model, a mixing enhancement number defined by the ratio of VD and PS mixing time further reveals the contribution from the variable-density effect, which implies a better control of density distribution for mixing enhancement in a supersonic streamwise vortex.
