Experimental study of the initial growth of a localized turbulent patch in a stably stratified fluid
| Autor: | Roi Gurka, Maarten van Reeuwijk, Lilly Verso, Zachary J. Taylor, Alex Liberzon, Peter Diamessis |
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| Rok vydání: | 2016 |
| Předmět: |
Entrainment (hydrodynamics)
Technology Buoyancy FLOW Flow (psychology) FOS: Physical sciences physics.ao-ph engineering.material Kinetic energy Mechanics 0915 Interdisciplinary Engineering 01 natural sciences 0901 Aerospace Engineering 010305 fluids & plasmas REGION 010309 optics WAKES Physics::Fluid Dynamics Optics Engineering 0103 physical sciences Local entrainment and stable stratification Mechanical Engineering & Transports COLLAPSE Fluid Flow and Transfer Processes Physics Science & Technology Turbulence business.industry Mechanical Engineering Internal wave Condensed Matter Physics Turbulent patch EVOLUTION Engineering Mechanical Physics - Atmospheric and Oceanic Physics Particle image velocimetry Planar laser-induced fluorescence INTERNAL WAVES Physical Sciences Atmospheric and Oceanic Physics (physics.ao-ph) engineering Thermodynamics SHEAR business BREAKING 0913 Mechanical Engineering |
| DOI: | 10.48550/arxiv.1603.06516 |
| Popis: | We present a laboratory experiment of the growth of a turbulent patch in a stably stratified fluid, due to a localized source of turbulence, generated by an oscillating grid. Synchronized and overlapping particle image velocimetry and planar laser induced fluorescence measurements have been conducted capturing the evolution of the patch through its initial growth until it reached a maximum size, followed by its collapse. The simultaneous measurements of density and velocity fields allow for a direct quantification of the degree of mixing within the patch, the propagation speed of the turbulent/non-turbulent interface and its thickness. The velocity measurements indicate significant non-equilibrium effects inside the patch which are not consistent with the classical used grid-action model. A local analysis of the turbulent/non-turbulent interface provides direct measurements of the entrainment velocity $w_{e}$ as compared to the local vertical velocity and turbulent intensity at the proximity of the interface. It is found that the entrainment rate $E$ is constrained in the range of $0{\div}0.1$ and that the local, gradient Richardson number at the interface is $\mathcal{O} (100)$. Finally, we show that the mean flow is responsible for the patch collapse. Comment: 25 pages, 13 figures |
| Databáze: | OpenAIRE |
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