Simultaneous velocity and density measurements of fully developed Rayleigh-Taylor mixing

Mikhaeil, Mark; Suchandra, Prasoon; Ranjan, Devesh; Pathikonda, Gokul

doi:10.1103/physrevfluids.6.073902

Cited by 2 publications

(27 citation statements)

References 67 publications

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“…Here u, v and w denote velocity components along x, y and z coordinates, respectively, with Ū or ū denoting mean component of the velocity and u denoting the fluctuating component, and so on. The previous gas tunnel used (in Akula & Ranjan 2016;Akula et al 2017;Mikhaeil 2020;Mikhaeil et al 2021) limits data collection and is limited in performance for a number of reasons. Several of those reasons, along with the advantages offered by the new three-layer gas tunnel, are addressed here.…”

Section: Experimental Facilitymentioning

confidence: 99%

“…The relevant length scales expected to be present in the new three-layer blow-down facility are estimated here. Similar methodology is presented in Mikhaeil (2020). The outer length scale of the flow is of the order of the mixing width and the fluctuating velocity scale is assumed to be of the order of the mixing width growth rate.…”

Section: Scales For Imaging Diagnosticsmentioning

confidence: 99%

“…Like the Kolmogorov microscale, dimensional arguments (Tennekes & Lumley 1972;Pope 2000) can be used to find an estimate for the Taylor microscale in terms of the mixing width and mixing Reynolds number, given by λ T = h 3 √ 10Re −1/2 and reported in table 1. The measurement of the Taylor microscale in the flow is important to check if there is enough separation between different length scales (mixing width versus Taylor microscale versus Kolmogorov microscale) and if the flow transitions to a turbulent state (Tennekes & Lumley 1972;Pope 2000;Mikhaeil 2020). Therefore, it is vital that our measurement diagnostics resolve the Taylor microscale.…”

Section: Scales For Imaging Diagnosticsmentioning

confidence: 99%

“…The vertical turbulent mass flux ρ v is the dominant term and a primary driver of Rayleigh-Taylor turbulence. Mikhaeil (2020) and Mikhaeil et al (2021) further modified the gas tunnel of Akula (2014) and Akula & Ranjan (2016) to implement laser induced fluorescence (LIF) and used PIV-LIF to obtain simultaneous velocity-density line measurements in low Atwood number RTI-affected flows. These simultaneous measurements gave a deep insight into turbulent kinetic energy transport equation budget for RTI-affected flows.…”

Section: Introductionmentioning

confidence: 99%

“…These simultaneous measurements gave a deep insight into turbulent kinetic energy transport equation budget for RTI-affected flows. More details on recent advancements in the study of instability-driven flows (particularly RTI-affected flows) can be found in Zhou (2017a,b), Banerjee (2020), Schilling (2020), Mikhaeil (2020), Mikhaeil et al (2021) and Suchandra (2022).…”

Section: Introductionmentioning

confidence: 99%

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Dynamics of multilayer Rayleigh–Taylor instability at moderately high Atwood numbers

Suchandra,

Ranjan

2023

J. Fluid Mech.

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This paper investigates the multilayer Rayleigh–Taylor instability (RTI) using statistically stationary experiments conducted in a gas tunnel. Employing diagnostics such as particle image velocimetry (PIV) and planar laser induced fluorescence (PLIF), we make simultaneous velocity–density measurements to study how dynamics and mixing are linked in this variable density flow. Experiments are conducted in a newly built, blow-down three-layer gas tunnel facility. Mixing between three gas streams is studied, where the top and bottom streams are comprised of air, and the middle stream is an air–helium mixture. Shear is minimized between these streams by matching their inlet velocities. The four experimental conditions investigated here consist of two different density ratios (Atwood numbers 0.3 and 0.6), each investigated at two instability development times (or equivalently, two streamwise locations), and all experiments are with the same middle stream thickness of 3 cm. The growth of the middle layer is measured using laser-based planar Mie scattering visualization. The mixing width is found to grow linearly with time at late times. Various quantitative measures of molecular mixing indicate a very high degree of molecular mixing at late times in the multilayer RTI flow. The vertical turbulent mass flux $a_y$ is calculated. In addition to mostly negative values of $a_y$ , typical of buoyancy-dominated flows due to negative correlation between velocity and density fluctuations, positive regions are also observed in profiles of $a_y$ due to entrainment and erosion at the lower edge of the mixing region. Global energy budgets are calculated for the multilayer RTI flow at late times and it is found that the majority of potential energy released has been dissipated due to viscous effects, and a large value of mixing efficiency ( $\sim$ 60 %) is observed.

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Section: Experimental Facilitymentioning

confidence: 99%

Section: Scales For Imaging Diagnosticsmentioning

confidence: 99%