Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session Y29: Multiscale simulation of complex fluid flowsFocus
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Sponsoring Units: DCOMP DFD Chair: Anthony Ladd, Univ of Florida - Gainesville Room: LACC 406A |
Friday, March 9, 2018 11:15AM - 11:51AM |
Y29.00001: Numerical Simulation of Turbulent Flows Invited Speaker: Parviz Moin Turbulent flows are ubiquitous in nature, affecting daily life from atmospheric dynamics to the mixing of fuel and oxidizer inside internal combustion engines, to the aerodynamics of modern aircraft. Multi-scale nature of turbulent flows creates challenges for numerical simulations. However, the exponential growth in computer power (about two orders of magnitude every 7 years) has enabled high fidelity numerical simulations of canonical turbulent flows at moderate Reynolds numbers possible. The data generated from such simulations are used to probe and gain insight into the physics of turbulent flows, and to conduct experiments of discovery not otherwise available in laboratory experiments. Results from recent numerical experiments that have shed light on the universality of the structure and dynamics of turbulence near solid boundaries will be presented. |
Friday, March 9, 2018 11:51AM - 12:03PM |
Y29.00002: Dewetting of Water-Isopropanol Monolayers Between MoS2 Membranes Beibei Wang, Rajiv Kalia, Aiichiro Nakano, Priya Vashishta Wetting and dewetting phenomena are important in the synthesis of layered materials by liquid-phase exfoliation. We perform molecular dynamics (MD) simulations to study dewetting of a monolayer of H2O and H2O-isopropanol (IPA) mixtures between two atomically thin MoS2 membranes. Our simulations reveal rapid dewetting in which dry patches on MoS2 move at a speed of 500 m/s with the solvent forming nanodroplets. The dynamic contact angles of solvent nanodroplets during dewetting are different from that of a standalone droplet on an MoS2 surface. We also investigate dewetting of H2O-IPA mixtures with different IPA concentrations. Results for the structure and dynamics of nanodroplets of water and H2O-IPA mixtures after dewetting will be reported. |
Friday, March 9, 2018 12:03PM - 12:15PM |
Y29.00003: The effects of the viscous pressure drop on the growth of a cluster of activated fractures Mohammed Alhashim, Donald Koch Convective transport in low permeable rocks can be enhanced by injection of a pressurized fluid to activate pre-existing weak planes (fractures). These fractures are initially closed, but fluid-pressure-induced slippage creates void space that allows fluid flow. Mohr’s criterion yields a critical pressure required to open each of the fractures. The activation process of a discrete well-connected network in a highly heterogeneous rock was simulated to analyze the process at a meso-scale that is larger than the average fractures’ length, λ, but smaller than the radius of a cluster of activated fractures, R . We show that depending on the ratio, FN , between the variability in the critical pressures and the viscous pressure drop, the activation process at large length scales can be described using continuum models. When FN << 1, the cluster is well connected, and a linear diffusion equation can be used to describe the cluster’s growth. When FN >> R/λ, a fractal network is formed by an invasion percolation process. In the intermediate regime, 1 << FN << R/λ, percolation theory relates the porosity and permeability of the network to the local pressure and a continuum diffusion model with pressure-dependent properties describes the cluster growth on length scales much larger than λFN. |
Friday, March 9, 2018 12:15PM - 12:27PM |
Y29.00004: On Relativistic Plasma/Non-vacuum Interaction Zephaniah Hernandez, Ecklin Crenshaw, Samina Masood There exists a limitation on plasma-based propulsion systems which restricts their usage to non-atmospheric environments. We theoretically determine the local effects of high temperatures and densities of relativistic plasmas through the generation of high thermal gradient, exhaust plumes. The interaction between the relativistic plasma exhaust and atmospheric regions of varying pressures in close proximity thereto are examined in an attempt to ascertain stability conditions and their associated stable regions. |
Friday, March 9, 2018 12:27PM - 1:03PM |
Y29.00005: TBD Invited Speaker: George Karniadakis Leading-edge work on multiscale modeling of red-blood-cells flow in capillary using impressive |
Friday, March 9, 2018 1:03PM - 1:15PM |
Y29.00006: Connecting lattice Boltzmann methods to underlying physical systems: Molecular Dynamics lattice Gas, Monte Carlo lattice Gas and their implications Alexander Wagner, Reza Parsa, Thomas Blommel Lattice Boltzmann simulations are becoming ever more popular for a large number of applications from high Reynolds number flows to multiphase flow in multicomponent mixtures. The method's succss has been credited to its relation to an underlying physical model which guarantees exact mass and momentum conservation. However, the relation back to physical systems has relied on matching appropriate dimensionless numbers, and the exact meaning of the lattice Boltzmann densities has remained obscure. By directly matching these densities to a coarse-grained grained Molecular Dynamics simulation we can show how these densities can be related to underlying physical quantities, and also where these direct identifications can become problematic. |
Friday, March 9, 2018 1:15PM - 1:27PM |
Y29.00007: How should lattice Boltzmann methods fluctuate? Evidence from the Molecular Dynamics Lattice Gas method M. Reza Parsa, Alexander Wagner We recently developed a coarse-graining method for Molecular Dynamics (MD) methods that represent MD results as effective lattice gas methods. We call this coarse-graining procedure Molecular Dynamics Lattice Gas (MDLG). We derived an effective equilibrium distribution that can be related to the lattice Boltzmann equilibrium distribution. For an ideal gas we expect that the occupation numbers are independent and Poisson distributed. Our MDLG method recovers these expected fluctuations for dilute gases, but correlations were observed for higher densities. We discuss how these results should affect the development of fluctuating lattice Boltzmann methods beyond the ideal gas behavior. |
Friday, March 9, 2018 1:27PM - 1:39PM |
Y29.00008: Fluctuating Lattice Boltzmann for Diffusive Systems Kyle Strand, Alexander Wagner Lattice Boltzmann methods continue to increase in popularity due to their simplicity and computational efficiency. Since lattice Boltzmann techniques were derived as ensemble averages of lattice gas automata, fluctuations are not present. Fluctuations play a large role in the behavior of multiphase systems, especially near the critical point. The question of how to re-introduce fluctuations into lattice Boltzmann methods has received much attention. We present a lattice Boltzmann approach to fluctuations in an ideal diffusive system. We then examine the fluctuation behavior of non-ideal van der Waals systems. We recover the equations of motion in the hydrodynamic limit for both cases. In certain situations, the method requires correction terms to better match the desired physical system. In these cases, we introduce fourth-order corrections to the non-ideal van der Waals system to recover proper phase behavior. We conclude with an outlook for extending the ideal and non-ideal systems to full hydrodynamical systems. |
Friday, March 9, 2018 1:39PM - 1:51PM |
Y29.00009: Abstract Withdrawn |
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