On mixing enhancement by secondary baroclinic vorticity in a shock–bubble interaction

• DOI: 10.1017/jfm.2021.923
• Publication Date: 2021-11-26T11:49:52Z
• Authors: Hong Liu; Bin Yu; Bin Zhang; Yang Xiang
• Keywords: 0103 physical sciences; Fluid Dynamics (physics.flu-dyn); FOS: Physical sciences; Physics - Fluid Dynamics; 01 natural sciences

To investigate the intrinsic mechanism for mixing enhancement by variable-density (VD) behaviour, a canonical VD extracted from supersonic streamwise vortex protocol, shock–bubble interaction (SBI), is numerically studied and compared with counterpart of passive-scalar (PS) mixing. It meaningful to observe that maximum concentration decays much faster in SBI than PS regardless shock Mach number ( $Ma=1.22 - 4$ ). The quasi-Lamb–Oseen-type velocity distribution found analysing azimuthal stretches bubble. Meanwhile, SBI, an additional stretching enhanced secondary baroclinic vorticity (SBV) production contributes faster-mixing decay. underlying SBV-enhanced further revealed through density difference between light shocked bubble heavy ambient air. By combining SBV-accelerated model initial compression, novel time estimation theoretically proposed solving advection–diffusion equation under deformation field axisymmetric SBV-induced velocity. Based on model, number, defined ratio further, reveals contribution effect, which implies better control vortex.