Abstract : Interfaces and interfacial mixing and their non-equilibrium dynamics control a broad range of processes in nature, technology, industry, from supernovae and fusion to alternative energy sources and purification of water. Mathematically, these problems are extremely challenging to study in theory and in simulations. Analytically, one needs to solve the conservation laws, augmented with singular boundary value problem and ill-posed initial value problem. Numerical modeling imposes high demands on the accuracy, precision and the scale of computations. The mini-symposium builds upon recent achievements in understanding the dynamics of interfaces and mixing, and reports solutions for long-time challenges in fundamentals and applications.
Organizer(s) : Snezhana Abarzhi, James Glimm, Alexander Nepomnyashchy, Yasuhide Fukumoto
[05008] Generalized Ideal Momentum Jet Model for Non-Circular Nozzle Geometries in Turbulent Pressure-Atomized Liquid Jets: Theoretical and Experimental Comparison
Format : Online Talk on Zoom
Author(s) :
Fermin Franco-Medrano (Autonomous University of Baja California)
Abstract : We propose a generalized mathematical model for turbulent pressure-atomized liquid jets with non-circular nozzles and compare to experimental data. We obtain analytical expressions for the locally homogeneous two-phase flow properties as a function of gauge pressure, nozzle dimensions, and fluid densities. Interestingly, we find that the equations describing elliptical and rectangular nozzles are generalizations of those for circular nozzles. Strong correlation is observed between the experimental data and our model function for the elliptical nozzle jet velocity.
[03716] Front Tracking Simulations of reshocked Richtmyer-Meshkov Instability
Format : Talk at Waseda University
Author(s) :
Tulin Kaman (University of Arkansas)
Ryan Holley (University of Arkansas)
Abstract : In this talk, we present an increasingly accurate and robust front tracking method for the numerical simulations of re-shocked Richtmyer-Meshkov Instability (RMI) of an air/SF6 interface. The front-tracking with the weighted essentially non-oscillatory (WENO) schemes are compared with Collins and Jacob (2002) shock tube experiments. We study the effects of high-resolution high-order WENO simulations on the fine detail complex vortex roll-up structures and perform verification and validation studies to achieve good agreement between simulations and experiments.
[05070] A novel data analysis method for Rayleigh-Taylor mixing
Format : Talk at Waseda University
Author(s) :
Kurt Christian Williams (The University of Western Australia)
Snezhana Abarzhi (University of Western Australia)
Abstract : A recent data analysis method has shed new light on the isotropy and dynamics of Rayleigh-Taylor mixing; the late-stage behavior of two fluids accelerated against their density gradient. In this talk, we elaborate this data analysis method, which employs Whittle estimates based on a new goodness-of-fit test statistic generated from Monte-Carlo methods. Employing a fitting function from isotropic turbulence, the method finds the isotropy of Rayleigh-Taylor
mixing and captures a broad dynamic range.
[03994] Nonlinear interaction of two nonuniform vortex interfaces and large vorticity amplification
Format : Talk at Waseda University
Author(s) :
Katsunobu Nishihara (Osaka University)
Chihiro Matsuoka (Osaka Metropolitan University)
Abstract : Vortex dynamics is an important research subject for geophysics, engineering and plasma physics. The nonlinear interaction of two nonuniform vortex interfaces with density stratification is investigated using the vortex sheet model. When a strong vortex sheet approaches a weaker vortex sheet with opposite-signed vorticity, a locally peaked secondary vorticity is induced on the latter sheet. This emerging secondary vorticity results in a remarkable vorticity amplification on the stronger sheet, forming pseudo vortex pairs.
Abstract : Smooth Navier-Stokes solutions require a non-physical choice of entropy minimization, achieved constructively as a mean value relative to turbulent fluctuations. Other solutions are not smooth. Drivers of the proof are a turbulence analogue of renormalized perturbation theory, adapted from Quantum Field theory, and shown to be Borel resummable convergent on a dense set of turbulent states, together with the Foias theory of Young measures.
[03969] Exact solutions to nonlinear difference equations associated with Henon maps
Format : Talk at Waseda University
Author(s) :
Chihiro Matsuoka (Osaka Metropolitan University)
Koichi Hiraide (Osaka Metropolitan University)
Abstract : We present exact solutions in non-integrable systems, taking the Henon map as an example. The obtained solutions describe the stable and unstable manifolds at saddle fixed points and make it possible to calculate such invariant manifolds with complex structures. Using the obtained functions, we visualize the hyperbolic system encircling KAM tori and the Henon attractor, in which chaotic orbits are captured accurately.
[03735] Can environmental and intrinsic mechanisms of quantum mixing be distinguished experimentally?
Format : Talk at Waseda University
Author(s) :
Alexander Y Klimenko (The university of Queesnland)
Alexander Y. Klimenko (The university of Queesnland)
Abstract : This presentation considers the possibility of quantum experiments that can, at least in principle, allow us to distinguish intrinsic and environmental mechanisms of decoherence. This experiment can be interpreted as a quantum-mechanical version of non-equilibrium mixing between two volumes separated by a thin interface. Decoherence is understood here as a general process that does not involve any significant exchanges of energy and is governed by a particular class of Kraus operators. This presentation considers different regimes of quantum tunnelling in the presence of different types of decoherence and shows that, at least under some conditions, intrinsic and environmental types of decoherence affect the tunnelling rates differently and, therefore, can be distinguished experimentally.
[04545] Special self-similar class in Rayleigh-Taylor interfacial mixing
Format : Talk at Waseda University
Author(s) :
Snezhana Abarzhi (University of Western Australia)
Abstract : Rayleigh-Taylor mixing governs a broad range of processes in nature and technology. We discover special self-similar class in Rayleigh-Taylor mixing with variable accelerations, by exploring its symmetries, scaling laws, correlations and fluctuations. We find that Rayleigh-Taylor mixing can vary from super-ballistics to sub-diffusion depending on the acceleration and retain memory of deterministic conditions for any acceleration. We explain high Reynolds number experiments in Rayleigh-Taylor mixing and provide new insights for processes driven by the mixing.
[04164] Compressible Kelvin-Helmholtz and Rayleigh-Taylor Instabilities
Format : Talk at Waseda University
Author(s) :
Yasuhide Fukumoto (Kyushu University)
Rong Zou (Zhejiang Normal University)
Kazuo Matsuura (Ehime University)
Nobutaka Taniguchi (University of Tokyo)
Abstract : For an incompressible fluid, an interface of tangential-velocity discontinuity suffers from the Kelvin-Helmholtz instability (KHI), with growth rate proportional to velocity discontinuity. Compressibility acts to stabilize KHI and, if limited to two dimensions, suppresses KHI for the Mach number larger than √8. We extend this analysis to include the gravity effect, with allowance made for density discontinuity and surface tension. Numerical simulations of a compressible mixing layer, being desingularization, exhibit complex vortical structures in turbulence.
[03293] Interaction between a particle and a liquid surface
Format : Talk at Waseda University
Author(s) :
Alexander Nepomnyashchy (Technion - Israel Institute of Technology)
Abstract : The interaction of a particle with a liquid interface takes place in many engineering processes. We consider the motion of a spherical particle rising in a viscous fluid towards the interface. The particle mobility can be significantly modified
by a surfactant adsorbed on the interface. Upon the particle attachment to the interface, the spatial inhomogeneity of
the wetting properties on the particle surface strongly enhance the duration of the system equilibration.
02578 (4/4) : 2E @G704 [Chair: Nepomnyashchy, Alik]
[04546] Interface dynamics in ideal and realistic fluids
Format : Talk at Waseda University
Author(s) :
Dan V. Ilyin (California Institute of Technology)
Snezhana Abarzhi (University of Western Australia)
Abstract : Interfaces and mixing and their non-equilibrium dynamics are ubiquitous to occur in nature and technology. We develop theory of interface dynamics, directly linking flow fields and interfacial transport and discovering fluid instabilities never previously discussed. In ideal and realistic fluids, the interface stability is set by the interplay of the macroscopic inertial mechanism balancing the destabilizing acceleration, whereas microscopic thermodynamics create vortical fields in the bulk. The interface is the place where balances are achieved.
[03416] Determining control parameters for unsteady pulling of mass-spectrometry emitters
Format : Talk at Waseda University
Author(s) :
Yvonne Stokes (The University of Adelaide)
Gagani Pathumika Ranathunga (Oktal Sydac)
Michael Chen (The University of Adelaide)
Abstract : Asymptotic modelling is used to examine the heating and pulling of an axisymmetric glass tube with an internal overpressure to form a taper with near-uniform bore and small wall thickness at the tip, as desired for mass-spectrometry emitters. There is no unique choice of pulling force and pressure to achieve the desired geometry, which is sensitive to the parameters. Phase plane plots are used to understand the dependence of the geometry on the control parameters.
[04478] Compressible Vortex Sheets and Free Boudary Problems
Format : Online Talk on Zoom
Author(s) :
Gui-Qiang George Chen (University of Oxford)
Abstract : We are concerned with the nonlinear stability/instability of compressible vortex sheets and related interfaces in compressible fluid flows governed by the Euler equations and related nonlinear PDEs. Such problems can be formulated as characteristic free boundary problems for nonlinear hyperbolic conservation laws and related equations. In this talk, we will discuss some recent developments in the analysis of their stability/instability and explore stabilizing mechanisms such as magnetic, relativistic, and compressibility effects.
