rayleigh-taylor driven mixing in a multiply stratified environment andrew lawrie & stuart...
DESCRIPTION
Prior Work Experimental setup –Dalziel et al. (1999) JFM Multiple stratifications –Jacobs & Dalziel (2005) JFM Incompressible Simulation –Almgren et al. (1998) JCPTRANSCRIPT
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Rayleigh-Taylor Driven Mixing in a Multiply Stratified
Environment
Andrew Lawrie & Stuart Dalziel,Andrew Lawrie & Stuart Dalziel,Department of Applied Mathematics and Theoretical PhysicsDepartment of Applied Mathematics and Theoretical Physics
University of Cambridge, UKUniversity of Cambridge, UK
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Outline
• Molecular mixing in the early stages of RT
• LIF with passive tracers
• MILES/ILES simulation
• Implications for Front-Tracking schemes
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Prior Work
• Experimental setup– Dalziel et al. (1999) JFM
• Multiple stratifications– Jacobs & Dalziel (2005) JFM
• Incompressible Simulation– Almgren et al. (1998) JCP
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Experimental Setup
Atwood No. = 0.0037
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Passive Tracer Transport
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LIF with Passive Tracers
• Chemically benign tracer
• Chemically reactive tracer
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Chemically Reactive Tracer
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Calibration
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Numerical Approaches
• Front-Tracking
• Spectral
• TVD-Finite Volume
• Mass diffusion affects 2Agth (George et al. 2002)
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Simulation
• Incompressible
• Immiscible
• Boussinesq
0.
0.
0.
1. 2
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Ut
kgUpUUtU
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Comparison
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Fractal Dimension
dimension fractal
size1)size(nboxes
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Mixing Surface
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Mixed Volume
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0Nondimensional Simulation Time
0.0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5Fr
actio
nal a
rea
ExperimentSimulation
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Conclusions
• Molecular mixing in the early stages of RT has been directly visualised with LIF
• Arguments based on growth rate used to justify accuracy of Front-Tracking schemes are shown to be inaccurate
• MILES simulations appear to provide a reasonable approximation to the mixing behaviour
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Further Work• Turbulent Diffusion over stable density interface
• Isolated vortex |ring impingement on stable density interface
• Influence of interfacial shear on turbulent diffusion
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Prior Research• Experimental setup
– eg. Self-similarity and internal structure of turbulence induced by Rayleigh-Taylor instability (1999) Dalziel, S. B.,Linden, P. F., Youngs, D. L. Journal of Fluid Mechanics
• Multiple stratifications– Rayleigh-Taylor Instability in Complex Stratifications (2005) Jacobs, J. W. Dalziel, S.B.
Journal of Fluid Mechanics
• Incompressible Simulation– A Conservative Adaptive Projection Method for the Variable Density Incompressible
Navier-Stokes Equations (1998) Almgren, A.S., Bell J.B.,Collela, P., Howell, L.H., Welcome, M.L. Journal of Computational Physics
• Front Tracking Simulation– A comparison of experimental theoretical an numerical simulation rayleigh-taylor mixing
rates. (2002) George, E., Glimm, J., Li, X.-L., Marchese, A., Xu, Z.-L. Proc. Natl. Acad. Sci.
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Laboratory
• Acridine +Alcohol
• 2,3,5,6, - dibenzopyridine