Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session B29: Interfaces and MixingInvited Live Streamed
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Sponsoring Units: DFD Chair: Nikolaus Adams, Tech Univ Muenchen Room: McCormick Place W-190B |
Monday, March 14, 2022 11:30AM - 12:06PM |
B29.00001: Interface dynamics in ideal and realistic fluids Invited Speaker: Snezhana I Abarzhi Interface and mixing and their non-equilibrium kinetics and dynamics couple micro to macro scales. They are ubiquitous to occur in fluids, plasmas and materials, over scales of celestial to atoms. The understanding of interfaces and mixing has crucial importance for science, mathematics and technology. Stellar evolution, plasma fusion, reactive fluids, purification of water, and nano-fabrication are a few examples of many processes to which dynamics of interfaces is directly relevant. This talk yields the theory of interface stability to rigorously solve a singular boundary value problem at a freely evolving unstable discontinuity – a task even more challenging than the Millennium problem on the Navier-Stokes equation. We directly link the structure of macroscopic flow fields with microscopic interfacial transport, quantify the contributions of macro and micro stabilization mechanisms to interface stability, and discover fluid instabilities never previously discussed. In ideal and realistic fluids, the interface stability is set primarily by the interplay of the macroscopic inertial mechanism balancing the destabilizing acceleration, whereas microscopic thermodynamics create vortical fields in the bulk. By linking micro to macro scales, the interface is the place where balances are achieved. Scale-invariant dynamics of unstable interfacial mixing belongs to a special self-similar class. |
Monday, March 14, 2022 12:06PM - 12:42PM |
B29.00002: Kadanoff Prize (2022): TBD Invited Speaker: K. R Sreenivasan TBD |
Monday, March 14, 2022 12:42PM - 1:18PM |
B29.00003: Impact of Numerical Hydrodynamics in Coarse Grained Simulations of Turbulent Material Mixing Invited Speaker: Fernando F Grinstein Underresolved simulations are typically unavoidable in high Reynolds (Re) and Mach (Ma) number turbulent flow applications at scale. Implicit Large-Eddy Simulation (ILES) often becomes the effective strategy to capture the dominating effects of convectively driven flow instabilities. ILES modeling can be based on effectively codesigned physics and numerics solving the compressible conservation equations with non-oscillatory finite-volume algorithms. We evaluate distinct numerical strategies for ILES and assess their impact simulating onset, development, and decay of turbulence: i) the Harten-Lax-van Leer (HLL) Riemann solver applying Strang splitting and a Lagrange-plus-Remap formalism to solve the directional sweep; ii) the Harten-Lax-Van Leer-Contact (HLLC) Riemann solver using a directionally unsplit strategy and parabolic reconstruction; and iii) the said unsplit scheme with added Low-Ma Correction (LMC) – denoted unsplit*. The LMC addresses the problem of excessive leading numerical dissipation ~1/Ma associated with upwinding critical in many applications of interest where most of the mixing actually occurs where the flow is weakly compressible. Modified equation analysis, a technique for generating approximate equations for the computed solutions, is used to elucidate the subgrid models associated with the algorithms underlying ILES. Fundamental case studies considered in this presentation include, homogeneous isotropic turbulence, the Taylor-Green Vortex, Rayleigh-Taylor flow, and shock-tube studies. For given spatiotemporal grid resolution, significantly more accurate predictions (reduced numerical uncertainties) are provided by the unsplit discretizations, specially when augmented with the LMC. Relevant comparisons of ILES based on Euler and Navier-Stokes equations are presented. Overall, the unsplit* reveals instrumental in capturing the spatiotemporal development and their validation on coarser grids. |
Monday, March 14, 2022 1:18PM - 1:54PM |
B29.00004: A dual scale LES model for interface dynamics Invited Speaker: Marcus Herrmann While significant progress has been made in the past decade to predict atomization using detailed numerical simulations, these come at significant computational cost since the range of scales that must be resolved exceeds those of a single phase turbulent flow significantly. A switch to a Large Eddy Simulation (LES) approach would be desirable, however, the underlying assumption of LES methods that the dynamics of the unresolved sub-filter scale can be inferred from the resolved scales is questionable when atomization occurs. Similar to viscosity in single-phase flows, surface tension scales with the inverse of a length-scale, but unlike viscosity, it can act to either dissipate surface corrugations preventing breakup, giving rise to the Hinze scale, or enhance surface corrugations due to the Rayleigh-Plateau instability, resulting in breakup. Which process is dominant on the sub-filter scale seems to depend entirely on the sub-filter interfacial geometry, i.e., if the interface is in the shape of ligaments, the surface tension can lead to breakup, whereas in other cases, surface-tension forces can inhibit breakup. Unfortunately, the sub-filter geometry cannot be inferred from the filtered interfacial geometry alone. LES approaches going beyond the traditional single-phase cascade hypothesis may be required for two-phase flows with atomization. |
Monday, March 14, 2022 1:54PM - 2:30PM |
B29.00005: Beyond Richtmyer-Meshkov Instability Invited Speaker: Peter Vorobieff Richtmyer-Meshkov instability (RMI) develops on an impulsively accelerated, initially perturbed density interface in fluid. The stability problem for such an interface can be initially considered using the same simplifications as Kelvin-Helmholtz and Rayleigh-Taylor instabilities: ideal fluid, two dimensions, small perturbations. This work was carried out by R.D. Richtmyer in the late 1950s, and the first experimental observations of RMI were published by E.E. Meshkov in the 1960s. Since then, major progress was made in understanding RMI, which is relevant to a large number of problems, from astronomy to engineering. The focus of this talk is on many of these problems where the classical formulation fails to describe either the complexity of the situation or the dominant instability mechanism. An important case of the former is shock interaction with a multiphase medium, where a macroscopic density interface may not exist, but volume-averaged density is non-uniform. Such an interaction can lead to vortex formation due to shock-driven multiphase instability (SDMI). An example of the latter (dominant instability) is shock interaction with a planar density interface at an angle to the plane of the shock. Vorticity deposition mechanism in this case is the same as for RMI, but it results in formation of a vortex sheet developing into shock-driven Kelvin-Helmholtz instability. We discuss the possibility of formulating a generalized framework for these problems, including introduction of dimensionless parameters and scale selection mechanisms. |
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