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. Multiscale 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 WaterIsopropanol Monolayers Between MoS_{2} Membranes Beibei Wang, Rajiv Kalia, Aiichiro Nakano, Priya Vashishta Wetting and dewetting phenomena are important in the synthesis of layered materials by liquidphase exfoliation. We perform molecular dynamics (MD) simulations to study dewetting of a monolayer of H_{2}O and H_{2}Oisopropanol (IPA) mixtures between two atomically thin MoS_{2} membranes. Our simulations reveal rapid dewetting in which dry patches on MoS_{2} 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 MoS_{2 }surface. We also investigate dewetting of H_{2}OIPA mixtures with different IPA concentrations. Results for the structure and dynamics of nanodroplets of water and H_{2}OIPA 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 preexisting weak planes (fractures). These fractures are initially closed, but fluidpressureinduced 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 wellconnected network in a highly heterogeneous rock was simulated to analyze the process at a mesoscale 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, F_{N} , 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 F_{N} << 1, the cluster is well connected, and a linear diffusion equation can be used to describe the cluster’s growth. When F_{N} >> R/λ, a fractal network is formed by an invasion percolation process. In the intermediate regime, 1 << F_{N} << R/λ, percolation theory relates the porosity and permeability of the network to the local pressure and a continuum diffusion model with pressuredependent properties describes the cluster growth on length scales much larger than λF_{N}. 
Friday, March 9, 2018 12:15PM  12:27PM 
Y29.00004: On Relativistic Plasma/Nonvacuum Interaction Zephaniah Hernandez, Ecklin Crenshaw, Samina Masood There exists a limitation on plasmabased propulsion systems which restricts their usage to nonatmospheric 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 Leadingedge work on multiscale modeling of redbloodcells 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 coarsegrained 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 coarsegraining method for Molecular Dynamics (MD) methods that represent MD results as effective lattice gas methods. We call this coarsegraining 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 reintroduce 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 nonideal 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 fourthorder corrections to the nonideal van der Waals system to recover proper phase behavior. We conclude with an outlook for extending the ideal and nonideal systems to full hydrodynamical systems. 
Friday, March 9, 2018 1:39PM  1:51PM 
Y29.00009: Abstract Withdrawn 
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