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Dzwinel, W. and D.A. Yuen, "Mixing Driven by RayleighTaylor Instability in the Mesoscale Modeled with Dissipative Particle
Dynamics", International J. of Modern Physics C, Vol. 12, No. 1, 91118, 2001.
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Mixing driven by RayleighTaylor Instability in the Mesoscale
Modelled with Dissipative Particle Dynamics
Witold Dzwinel
AGH Institute of Computer Science, al. Mickiewicza 30, 30059, Kraków, Poland
David A.Yuen
1
Minnesota Supercomputer Institute, University of Minnesota, Minneapolis, Minnesota 55415
1227, USA
Abstract
In the mesoscale mixing dynamics involving immiscible fluids is truly an outstanding problem in
many fields, ranging from biology to geology, because of the multiscale nature, which causes
severe difficulties for conventional methods using partial differential equations. The existing
macroscopic models incorporating the two microstructural mechanisms of breakup and
coalescence do not have the necessary physical ingredients for feedback dynamics. We
demonstrate here that the approach of dissipative particle dynamics (DPD) does include the
feedback mechanism and thus can yield much deeper insight into the nature of immiscible
mixing. We have employed the DPD method for simulating numerically the highly nonlinear
aspects of the RayleighTaylor (RT) instability developed over the mesoscale for viscous,
immiscible, elastically compressible fluids. In the initial stages we encounter the spontaneous,
vertical oscillations in the incipient period of mixing.
The long term dynamics are controlled by the
initial breakup and the subsequent coalescence of the microstructures and the termination of the
chaotic stage in the development of the RT instability. In the regime with high capillary number
breakup plays a dominant role in the mixing, whereas in the low capillary number regime the flow
decelerates and coalescence takes over and causes a more rapid turnover. The speed of mixing
and the turnover depend on the immiscibility factor, which results from microscopic interactions
between the binary fluid components. Both the speed of mixing and the overturn dynamics
depend not only on the mascrocopic fluid properties, but also on the breakup and coalescent
patterns, and most importantly on the nonlinear interactions between the microstructural
dynamics and the largescale flow .
Keywords:
RayleighTaylor mixing, mesoscopic fluids, immiscible fluids, breakup and
coalescence morphology, dissipative particle dynamics (DPD)
1
corresponding Author,
Minnesota Supercomputing Institute, University of Minnesota, 1200 Washington Av. South,
Minnesota, 554151227, USA email:
davey@krissy.msi.umn.edu
fax: 612 624 8861
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View Full DocumentDzwinel, W. and D.A. Yuen, "Mixing Driven by RayleighTaylor Instability in the Mesoscale Modeled with Dissipative Particle
Dynamics", International J. of Modern Physics C, Vol. 12, No. 1, 91118, 2001.
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