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Rayleigh-Taylor Driven Mixing in a Multiply Stratified Environment

Rayleigh-Taylor Driven Mixing in a Multiply Stratified Environment. Andrew Lawrie & Stuart Dalziel, Department of Applied Mathematics and Theoretical Physics University of Cambridge, UK. Outline. Molecular mixing in the early stages of RT LIF with passive tracers MILES/ILES simulation

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Rayleigh-Taylor Driven Mixing in a Multiply Stratified Environment

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  1. Rayleigh-Taylor Driven Mixing in a Multiply Stratified Environment Andrew Lawrie & Stuart Dalziel, Department of Applied Mathematics and Theoretical Physics University of Cambridge, UK

  2. Outline • Molecular mixing in the early stages of RT • LIF with passive tracers • MILES/ILES simulation • Implications for Front-Tracking schemes

  3. Prior Work • Experimental setup • Dalziel et al. (1999) JFM • Multiple stratifications • Jacobs & Dalziel (2005) JFM • Incompressible Simulation • Almgren et al. (1998) JCP

  4. Experimental Setup Atwood No. = 0.0037

  5. Passive Tracer Transport

  6. LIF with Passive Tracers • Chemically benign tracer • Chemically reactive tracer

  7. Chemically Reactive Tracer

  8. Calibration

  9. Numerical Approaches • Front-Tracking • Spectral • TVD-Finite Volume • Mass diffusion affects (George et al. 2002)

  10. Simulation • Incompressible • Immiscible • Boussinesq

  11. Comparison

  12. Fractal Dimension

  13. Mixing Surface

  14. Mixed Volume

  15. 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

  16. Further Work • Turbulent Diffusion over stable density interface • Isolated vortex |ring impingement on stable density interface • Influence of interfacial shear on turbulent diffusion

  17. 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.

  18. Laboratory • Acridine +Alcohol • 2,3,5,6, - dibenzopyridine

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