Bulletin of the American Physical Society
72nd Annual Meeting of the APS Division of Fluid Dynamics
Volume 64, Number 13
Saturday–Tuesday, November 23–26, 2019; Seattle, Washington
Session Q19: CFD: Immersed Boundary Methods II |
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Chair: Andres Goza, University of Illinois at Urbana-Champaign Room: 401 |
Tuesday, November 26, 2019 7:45AM - 7:58AM |
Q19.00001: A Fully Grid-Line-Based Immersed Boundary Method Guanting Su, Tianyu Pan, Qiushi Li By introducing proper variable reconstruction scheme in the vicinity of immersed boundaries, a group of immersed boundary methods (IBMs), including ghost-cell method and hybrid Cartesian method, showed promising performance when simulating unsteady, incompressible flow around complex boundaries using non-body-conformal orthogonal grids. In this work, we propose a fully grid-line-based IBM with a novel velocity reconstruction scheme which is capable of stably imposing desired linear velocity distribution along single or multiple gridline directions. Pressure boundary condition is inherently implemented with desired velocity distribution imposed. Present method greatly simplifies boundary-related operations by eliminating existing need to search for projections along off-gridline direction (e.g. normal to boundary). And with utilization of standard discretization stencils enabled on boundary-adjacent grid nodes, implicit time advancement of viscous term is straightforward. Flow simulation results are in good agreement with reference data and show that the proposed method retains second-order accuracy of the fractional-step Navier-Stokes solver incorporated. [Preview Abstract] |
Tuesday, November 26, 2019 7:58AM - 8:11AM |
Q19.00002: An Efficient Immersed-Boundary Formulation with Explicit Time Stepping for Incompressible Flows Noah Osman One of the most persistent difficulties in numerically simulating incompressible flow problems is the treatment of the stiff diffusive term. In order to maintain stability, this term is traditionally treated using an implicit time-stepping method, necessitating the solution to a large linear system at each time step. A variety of efficient techniques have been developed to solve these linear systems. However, their application in the presence of non-uniform grids and other non-canonical numerical configurations remains a challenge. We consider an alternative approach in which the diffusive term is treated explicitly, with no severe restrictions on the time step size. We present our method within an immersed-boundary formulation to enable efficient simulations of flows involving immersed bodies. To do this, we extend the Runge-Kutta Chebyshev method of Van der Houwen and Sommeijer (1980) to the differential-algebraic setting relevant to the immersed-boundary method. We demonstrate the efficacy of the method through results from canonical 2D flow problems. [Preview Abstract] |
Tuesday, November 26, 2019 8:11AM - 8:24AM |
Q19.00003: Particle-resolved DNS(PR-DNS) to study the bulk settling velocity of poly-dispersed particles Yinuo Yao, Oliver Fringer, Craig Criddle A PR-DNS is implemented to investigate poly-dispersed particle hydrodynamics in triply-periodic flow. The particle motion is computed with a direct forcing IBM approach along with the collision model proposed by Biegert et al.(2017). The direct forcing method accurately predicts particle motions with moderate particle Reynolds numbers up to 360. To avoid the small time-step size needed to simulate collisions with the soft-sphere approach, we use the adaptive collision time model proposed by Kempe et al.(2012). Poly-dispersed particles are initialized randomly in two- and three-dimensions and subjected to gravity to settle while interacting with one another. Simulations are then run until the mean settling velocity, reaches steady state. This relates the velocity to mean particle Reynolds number. Different poly-disperse particle scenarios are devised that allow for the study of the effect of the particle size distribution while keeping other bulk properties fixed. The results are discussed in the context improving energy efficiency of the fluidized bed reactors in the wastewater treatment, which are characterized by the pressure loss due to motion of poly-dispersed particles in turbulent flow. This work is supported by California Energy Commission (CEC). [Preview Abstract] |
Tuesday, November 26, 2019 8:24AM - 8:37AM |
Q19.00004: Treatment of immersed boundaries for the Vortex Particle-Mesh method Thomas Gillis, Gregoire Winckelmans, Philippe Chatelain The Vortex Particle-Mesh (VPM) method combines the advantages of a particle method, i.e. low numerical dissipation and dispersion errors, with those of a Cartesian mesh-based approach: highly efficient Poisson solvers and finite difference stencils. However, the accurate treatment of the immersed boundaries in the VPM framework is still an open challenge as the formulation of the boundary condition for the vorticity is not as straightforward as in a classical velocity-pressure formulation. This complexity is further increased since the VPM method relies on a non-body-conforming Cartesian mesh; hence the obstacle may intersect the grid at arbitrary locations. The two current state-of-the-art methods are the (iterative) penalization approach and the Boundary Element Method coupled with the VPM approach. The first one, the penalization technique, suffers from a lack of accuracy due to the smearing of the interface, hence offering an unsatisfactory surface treatment. The second one, the Boundary Element Method (BEM) approach suffers from a first order time convergence due to the splitting of the diffusion operation. This presentation focuses on this challenge: the treatment of immersed boundaries in order to accurately predict the interactions between the fluid and these structures. [Preview Abstract] |
Tuesday, November 26, 2019 8:37AM - 8:50AM |
Q19.00005: An Immersed Boundary Method for Shock-Particle Interaction Iman Borazjani A sharp-interface immersed boundary method is developed to simulate the interaction of solid particles with shocks. The inviscid and viscous fluxes of compressible flow equations in curvilinear coordinates are discretized with a third order weighted essentially non-oscillatory (WENO) and a central scheme, respectively. The equations are advanced in time using a third-order Runge-Kutta method. The sharp interface at the immersed boundaries is maintained by reconstructing the compressible flow variables along the normal direction to the boundary similar to the previous method for incompressible flows. The WENO discretization is reverted to a second order ENO scheme near the immersed boundaries to reduce the stencil size and avoid using the nodes inside the immersed boundary in the discretization. The method is validated against experimental measurements and shown to be second-order accurate in the presence of immersed boundaries. The numerical results capture all of the shock features observed in the experiments and show great agreement with the measurements. [Preview Abstract] |
Tuesday, November 26, 2019 8:50AM - 9:03AM |
Q19.00006: High Order Cut-cell Methods in Multiple Dimensions Peter Brady, Daniel Livescu Cut-cell methods for unsteady flow problems can greatly simplify the grid generation process and allow for high-fidelity simulations on complex geometries. However, cut-cell methods have been limited to low orders of accuracy. This is driven, largely, by the variety of procedures typically introduced to evaluate derivatives in a stable manner near the highly irregular embedded geometry. The present approach is based on two simple and intuitive design principles. These principles, and an a-priori optimization process, allow for the construction of stable 8th order approximations to elliptic and parabolic problems and stable and conservative 5th order approximations to hyperbolic problems. This is done for both explicit and compact finite differences and is accomplished without any geometric transformations, artificial stabilization or other adhoc in-situ procedures. Test cases with 2-D and 3-D geometries will be discussed. [Preview Abstract] |
Tuesday, November 26, 2019 9:03AM - 9:16AM |
Q19.00007: Advanced immersed boundary method for complex moving/morphing boundaries based on hybrid ghost-cell and virtual cut-cell Kamau Kingora, Hamid Sadat The state of art of sharp interface immersed boundary (IB) methods (cut-cell and ghost-cell (GC) methods) today is that they lack generality and are specialized in nature. Consequently, their extension to problems with multiple potentials is not straightforward. We propose an accurate and robust advanced immersed boundary method (AIBM) for simulation of fluid structure interaction (FSI) in complex flow. This novel sharp interface IB method entails addition of a generic virtual force to the underlying governing equation for the purpose of enforcing desired boundary conditions on different field variables like velocity, temperature, chemical species etc. AIBM employs virtual cut-cell techniques which makes AIBM easy to implement and parallelize, and also applicable to multiphase flow on grid with high aspect ratio, unlike GC method which rely on interpolation. Solid part of simulation domain is logically eliminated from computation matrix hence AIBM is capable of simulating internal and/or external flow with large number of cells in the solid region. Fresh-cell problem is tackled by a field extension technique, enabling AIBM to simulate FSI with moving and/or deforming boundary without pressure oscillations and spurious forces. We validated the proposed method by running benchmark cases using our in-house solver, CFDFoam. The results predicted by AIBM are in good agreement with experimental studies. [Preview Abstract] |
Tuesday, November 26, 2019 9:16AM - 9:29AM |
Q19.00008: Internal Flow Analysis in an Axial Pump using Large-eddy Simulation with Immersed Boundary Method Dandan Yang, Xianwu Luo, Lian Shen Axial flow pump is widely used in drainage, irrigation, and water diversion applications. A high-fidelity numerical method is needed to study the flow physics and accurately predict the pump performance. In the present work, the transient flow past an axial pump, comprised of the hub, casing, a rotating impeller and a stationary stator, is simulated by large-eddy simulation with the immersed boundary method using a code developed in-house, which is capable of accurately simulating the turbulent flow with three dimensional complex geometries with stationary and moving boundaries. The accuracy of the present simulation method is verified by comparing the predicted hydraulic performance of the pump with experimental results. Based on the simulation results, the internal flow field in the pump is analyzed by investigating velocity and pressure distributions, and turbulent flow structures. Further, pressure oscillation and hydraulic force in the pump are also predicted. The obtained information is helpful to improve the pump design for better performance. [Preview Abstract] |
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