Bulletin of the American Physical Society
65th Annual Meeting of the APS Division of Fluid Dynamics
Volume 57, Number 17
Sunday–Tuesday, November 18–20, 2012; San Diego, California
Session G3: Multiphase Flows: Numerical Methods I |
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Chair: Carlos Coimbra, University of California, San Diego Room: 23B |
Monday, November 19, 2012 8:00AM - 8:13AM |
G3.00001: Effect of gravity on particle dispersion in upward gas turbulent channel flow Yoichi Mito Fully-developed concentration fields of solid particles with a large range of inertial time constants in a plane channel in which gas is flowing turbulently in the upward direction are calculated by using direct numerical simulation to calculate the gas velocities seen by particles and a Lagrangian method to calculate trajectories of particles. The objective is to examine the effects of gravity and of inertia, both of which represent trajectory mechanisms that decrease turbulent dispersion, on particle transport in wall-bounded turbulent flow. The frictional Reynolds number is 150. Density ratio is 1000. The Stokesian inertial time constants made dimensionless with the friction velocity and kinematic viscosity are 5, 10, 20, 40, 100, 200. Three Froude numbers, Fr = 0.02, 5 and infinity, are considered. Forces exerted by particles on the gas and inter-particle collisions are not considered. Effect of gravity on particle dispersion is not seen at Fr $\ge $ 5. The particle turbulence decreases due to the effect of gravity at Fr = 0.02. The effect of gravity increases with increasing particle inertia and with increasing the distance from the wall. It disappears in the viscous wall region where particles are disengaged from gas turbulence structures due to their inertia. [Preview Abstract] |
Monday, November 19, 2012 8:13AM - 8:26AM |
G3.00002: ABSTRACT WITHDRAWN |
Monday, November 19, 2012 8:26AM - 8:39AM |
G3.00003: Dynamics of a cylinder plunging into liquid: a numerical study Hang Ding The impact of a cylinder on a liquid surface and subsequent events are investigated numerically. The flows are resolved by solving the Navier-Stokes equations and the Cahn-Hilliard equation. Moving contact lines are modeled by a diffuse interface model (Seppecher 1996; Jaqcmin 2000), and contact-angle hysteresis is included (Ding{\&}Spelt 2008). The method is validated by comparison to the experiments by Aristoff and Bush (2009). Our studies focus on the dynamics of the waves induced by the impact and the cavity collapse behind the cylinder. A variety of parameters affect the flow behaviors such as wettability, impact speed, viscosity etc. Their effects on the transition of the flow phenomena are investigated through parametric simulations over relevant ranges of Weber and Reynolds numbers and contact angles. [Preview Abstract] |
Monday, November 19, 2012 8:39AM - 8:52AM |
G3.00004: A conservative volume of fluid method for general grids in three dimensions Christopher Ivey, Parviz Moin A conservative advection scheme based on the use of edge-matched flux polyhedra to integrate the volume fraction evolution equation on general grids is presented. The algorithm prevents the formation of over/undershoots of the volume fraction by enforcing that the flux polyhedra do not over/underlap, removing the need for unphysical and inaccurate redistribution algorithms. The advection scheme is formally first order in volume fraction due to is upwinding nature; however, kinematic test cases performed on grids of varying structure and density demonstrate that the accuracy is between first and second order and nominally compares well with contemporary algorithms. [Preview Abstract] |
Monday, November 19, 2012 8:52AM - 9:05AM |
G3.00005: Improved connectivity free front tracking method for modeling contact lines in multiphase flow Chu Wang, Lucy Zhang A numerical algorithm is developed to simulate multiphase flows with contact lines by coupling dynamic contact line model into the connectivity free front tracking method (CFFT). The contact angle is specified dynamically with an empirical correlation related to the contact line velocity. The hysteresis of the contact angles is also included in the algorithm. This contact line model is coupled to the CFFT conveniently for its explicit representation of the interface. Also, the CFFT does not require the connectivity of the interfacial points to construct the indicator field by ensuring a constant indicator, e.g. I=0.5 coinciding with interface. The topology change of the interface including the contact lines can be treated automatically by adopting a simple points-regeneration scheme. RKPM interpolations are used to achieve better accuracy when constructing the indicator and calculating the normal for contact lines where the interfacial points are connected to the solid wall. Several test cases are performed to validate the method to show its accuracy and capability to simulate multiphase flows with contact lines that undergo frequent topology changes. [Preview Abstract] |
Monday, November 19, 2012 9:05AM - 9:18AM |
G3.00006: Shock-driven formation of a cloud from particles swept off a surface Patrick Wayne, Tennille Bernard, Clint Corbin, Garrett Kuehner, Peter Vorobieff, C. Randall Truman, Hugh Smyth, Andy Maloney We present an experimental study of respirable particle advection in shock-driven flow. Particles of specific size ($\leq 5 \ \mu$m) were ultrasonically deposited on surface samples, with sample roughness and other characteristics well-known. Then the samples were exposed to normal shocks at Mach number $\sim$1.67. Time-resolved visualizations of the resulting particle clouds provide insights into the physics of the flow. As the clouds evolve, they apparently extend into the flow beyond the wall boundary layer. Several interesting features have been observed, including formation of shear-driven Kelvin-Helmholtz instability on the edge of the cloud. Initial observations suggest a prominent relationship between the force of adhesion between the particles and the surface on one hand and the propagation speed of the particle cloud on the other hand. [Preview Abstract] |
Monday, November 19, 2012 9:18AM - 9:31AM |
G3.00007: A multiphase flow solver with adaptive mesh refinement Keegan Delaney, Elias Balaras, Zhipeng Qin, Amir Riaz We will present a scalable Navier-Stokes solver applicable to multiphase incompressible flows. The solver employs Level Set techniques to sharply define the interface between different phases (i.e. air and water). A fractional step method is used to solve the momentum and continuity equations, which results in a variable coefficient Poisson pressure equation. Proper jump conditions are applied to the Poisson pressure equation to accurately capture the jump in pressure that results from surface tension between different phases. Scalable linear solvers are used to solve the variable coefficient Poisson pressure equation on large core counts. Scalability and efficiency were placed at a premium during development of the solver, which has been tested to core counts on the order of 10,000. The solver takes advantage of Adaptive Mesh Refinement (AMR) to reduce overall cell count in the solution domain, thus reducing computational time. This feature allows for sufficient resolution of complex interfacial features without over-resolving areas of no interest. In the present work, the mesh is selectively refined around the multiphase interface, which is evolving in time. A wide range of multiphase problems will be presented to demonstrate the accuracy and efficiency of the solver. [Preview Abstract] |
Monday, November 19, 2012 9:31AM - 9:44AM |
G3.00008: A lattice based approach for simulation of multiphase flows with phase transitions Abdelaziz Aliat, Prakash Vedula We present a lattice based approach to address challenges due to nonequilibrium behavior in liquid-vapor flows with phase transitions. The effects of phase transitions are accounted for via an interaction potential that is treated as a combination of a short range repulsion model based on hard sphere interactions and a long range attraction tail based on mean field models. Particle distribution functions are evolved based on the Boltzmann equation with the full collision operator and a self-consistent force field. Our numerical implementation of this approach involves quadrature-based analytical approximations of moments due to the full collision operator and second-order accurate approximations to convective fluxes (including flux limiters). The results obtained from this approach will be compared with those from other approaches based on standard Lattice Boltzmann Method for simulation of phase transitions in selected canonical flows using different mean-field models. Generalizations of our proposed approach for accurate simulation of heat transfer rates based on high-order lattice representations will also be discussed. [Preview Abstract] |
Monday, November 19, 2012 9:44AM - 9:57AM |
G3.00009: ABSTRACT WITHDRAWN |
Monday, November 19, 2012 9:57AM - 10:10AM |
G3.00010: ABSTRACT WITHDRAWN |
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