Formation and dynamics of compressible vortex rings generated by a shock tube

Qin, Liang; Xiang, Yang; Lin, Haiyan; Liu, Hong

doi:10.1007/s00348-020-2920-1

Cited by 15 publications

(5 citation statements)

References 31 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: 66%

“…To quantify the velocity distribution, figure 7(c) gives the V θ along defined lines of different moments, as illustrated in figure 7(a). From figure 7(a1), it can be observed that the Mach stem intrudes the vortex core, which is called 'embedded shock' first found in a compressible vortex ring (Dora et al 2014;Qin et al 2020). Therefore, the defined Line 1 emerges in a high velocity region before encountering the Mach stem.…”

Section: Ps Mixing Mechanism: Vortical Stretching Mixingmentioning

confidence: 93%

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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: 66%

Section: Ps Mixing Mechanism: Vortical Stretching Mixingmentioning

confidence: 93%

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

Zhang

et al. 2021

J. Fluid Mech.

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“…20 micron thick aluminium foil is used as a diaphragm and is placed at the flange connection between the vacuum flange and driver part. The feasibility of the shock tube must be validated before any further improvements are considered, so no diaphragm-breaking system, such as that in the work of Qin et al (2020) and Xiang et al (2023), is added in the current work; the diaphragm is broken naturally through the pressure difference between the driver and the driven sections. The design and use of a diaphragm-breaking system is considered to be future work.…”

Section: Shock Tube Design Detailmentioning

confidence: 99%

Vortex Ring Formation Following Shock Wave Diffraction in Low-Pressure Environments

Cao,

Kontis,

Hosano

et al. 2023

Flow Turbulence Combust

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Compressible vortex rings have been widely investigated for decades under ambient atmospheric conditions, and understanding this transient phenomenon is important for improving the thrust vector and avoiding surface impingement and contamination. However, how the vortex ring behaves in a reduced pressure environment remains unknown. This work provides schlieren imaging and pressure measurement results of the vortex ring when the environmental pressure is lower than 1 atm. The basic structure of the compressible vortex ring in low-pressure environments has been captured. The reduced environmental pressure will degenerate the internal flow structure, including the shock wave, the CRVRs, and the vortices due to the Kelvin–Helmholtz instability, which is consistent with the conclusion of previous numerical work. The vortex ring is confirmed to exist when the environmental pressure is approximately 1.0 kPa.

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“…In general, calculating the centroid of the cross-section of a vortex loop is useful in evaluating its radius if such a vortex loop is a ring. Conventionally, the centroid of a vortex cross-section is based on the distribution of vorticity 32 . Here, the centroid of such a region can be calculated when rorticity components replace the vorticity.…”

Section: Geometrical Characteristics Of Rarefied Vortex Loopmentioning

confidence: 99%

Numerical investigation of rarefied vortex loop formation due to shock wave diffraction with the use of rorticity

2021

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When compressed gas is ejected from a nozzle into a low-pressure environment, the shock wave diffracts around the nozzle lip and a vortex loop will form. The phenomenon has been widely investigated in the continuum flow regime, but how the shock diffraction and vortex behave under rarefied flow conditions has not received as much attention. It is necessary to understand this transient flow in rarefied environments to improve thrust vector control and avoid potential contamination and erosion of spacecraft surfaces. This work provides numerical results of the vortex loop formation caused by shock wave diffraction around a 90 • corner using the direct simulation Monte Carlo method and the compressible Navier-Stokes equations with the appropriate Maxwell velocity slip and the von Smoluchowski temperature jump boundary conditions. The Mach number and rarefaction effects on the formation and evolution of the vortex loop are discussed. A study of the transient structures of vortex loops has been performed using the rorticity concept. A relationship of mutual transformation between the rorticity and shear vectors has been discovered, demonstrating that the application of this concept is useful to understand vortex flow phenomena.

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Formation and dynamics of compressible vortex rings generated by a shock tube

Cited by 15 publications

References 31 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

Vortex Ring Formation Following Shock Wave Diffraction in Low-Pressure Environments

Numerical investigation of rarefied vortex loop formation due to shock wave diffraction with the use of rorticity

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