Passive scalar mixing induced by the formation of compressible vortex rings

Lin, Haiyan; Xiang, Yang; Xu, Hanlin; Liu, Hong; Zhang, Bin

doi:10.1007/s10409-020-01006-6

Cited by 8 publications

(3 citation statements)

References 52 publications

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“…Sau & Mahesh (2007) conducted the first DNS simulation of passive-scalar (PS) mixing in a 3-D vortex ring. The optimal mixing from a vortex ring was also confirmed when the vortex grew to pinch-off status (Gharib, Rambod & Shariff 1998), which was recently also validated in the formation of a supersonic vortex ring (Lin et al 2020;Qin et al 2020). Such a simple PS mixing protocol offers ample phenomena that are resolvable to a near-exact solution, which attracts researchers and provides more in-depth mechanisms of stretching-enhanced diffusion characteristic of mixing (Villermaux 2019).…”

Section: Introductionmentioning

confidence: 65%

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

Zhang

et al. 2021

J. Fluid Mech.

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To investigate the intrinsic mechanism for mixing enhancement by variable-density (VD) behaviour, a canonical VD mixing extracted from a supersonic streamwise vortex protocol, a 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 a VD SBI than in a 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 analysing 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 light shocked 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 VD effect, which implies a better control of the density distribution for mixing enhancement in a supersonic streamwise vortex.

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Section: Introductionmentioning

confidence: 65%

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

Zhang

et al. 2021

J. Fluid Mech.

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“…2008), experiment (Maxworthy 1977; Glezer 1988; Cater, Soria & Lim 2004; Das, Bansal & Manghnani 2017) and numerical simulation (Shariff, Verzicco & Orlandi 1994; Archer, Thomas & Coleman 2008; Lin et al. 2020). However, for many practical situations, the formation and evolution of the vortex exist in a non-uniform or stratified environment, such as the wake of aircrafts and vessels in the stratified flow, convection of thermals in the inversion layer, interaction of flame fronts with the turbulent flow, diffusion of contaminants in the atmosphere and halocline in oceans (Dahm, Scheil & Tryggvason 1989; Sarpkaya 1996; Advaith et al.…”

Section: Introductionmentioning

confidence: 99%

“…Vortex rings (Shariff & Leonard 1992) have always played a crucial role in scientific research and engineering applications. Over the past few decades, the dynamics of the vortex ring evolving in a uniform environment has been well established in theory (Shusser & Gharib 2000;Krueger 2005;Sullivan et al 2008), experiment (Maxworthy 1977;Glezer 1988;Cater, Soria & Lim 2004;Das, Bansal & Manghnani 2017) and numerical simulation (Shariff, Verzicco & Orlandi 1994;Archer, Thomas & Coleman 2008;Lin et al 2020). However, for many practical situations, the formation and evolution of the vortex exist in a non-uniform or stratified environment, such as the wake of aircrafts and vessels in the stratified flow, convection of thermals in the inversion layer, interaction of flame fronts with the turbulent flow, diffusion of contaminants in the atmosphere and halocline in oceans (Dahm, Scheil & Tryggvason 1989;Sarpkaya 1996;Advaith et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Dynamics of the interaction of synthetic jet vortex rings with a stratified interface

Wang

Feng

2022

J. Fluid Mech.

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The vortex dynamics in a stratified environment is of fundamental importance in various flow systems, however, the mechanism of successive vortex–interface interactions remains not fully understood. This study investigates synthetic jet vortex rings impinging on a water–oil interface by experiment and numerical simulation. Two cases in the laminar and transitional regimes are concerned with the Froude number (Fr) of 0.35 and 0.82, respectively. The vortex rings for the two cases follow a similar evolution with three distinct stages, including vortex free-travel, vortex–interface interaction and vortex stretching. As products of the vortex–interface interaction, the secondary vortex rings are baroclinically generated in both water and oil followed by the formation of hairpin vortices through azimuthal deformation. Distinguished from an isolated vortex–interface interaction, complex interactions occur between the primary vortex ring and hairpin vortices, which can enhance the vortex ring instability in existence of the stratification for the laminar case. However, the vortex ring instability for the transitional case can develop earlier due to nonlinear effects with increasing Reynolds number. The spatio-temporal properties of the interface deformation and interfacial waves are analysed. The maximum penetration height of vortex rings scales with Fr2 as that for the isolated situation. Particularly, the transitional case is found to produce destabilization of the interfacial waves at a further radial location. The mechanism is revealed by connecting the dynamics of the vortex and the interface, which can be attributed to the radial development of perturbances stemming from the vortex ring instability under strong vortex–interface interaction.

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Scaling analysis of the circulation growth of leading-edge vortex in flapping flight

et al. 2021

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Passive scalar mixing induced by the formation of compressible vortex rings

Cited by 8 publications

References 52 publications

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

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

Dynamics of the interaction of synthetic jet vortex rings with a stratified interface

Scaling analysis of the circulation growth of leading-edge vortex in flapping flight

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