201 research outputs found
An immersed boundary method based on the lattice Boltzmann approach in three dimensions, with application
The immersed boundary (IB) method originated by Peskin has been popular in modeling and simulating problems involving the interaction of a flexible structure and a viscous incompressible fluid. The Navier–Stokes (N–S) equations in the IB method are usually solved using numerical methods such as FFT and projection methods. Here in our work, the N–S equations are solved by an alternative approach, the lattice Boltzmann method (LBM). Compared to many conventional N–S solvers, the LBM can be easier to implement and more convenient for modeling additional physics in a problem. This alternative approach adds extra versatility to the immersed boundary method. In this paper we discuss the use of a 3D lattice Boltzmann model (D3Q19) within the IB method. We use this hybrid approach to simulate a viscous flow past a flexible sheet tethered at its middle line in a 3D channel and determine a drag scaling law for the sheet. Our main conclusions are: (1) the hybrid method is convergent with first-order accuracy which is consistent with the immersed boundary method in general; (2) the drag of the flexible sheet appears to scale with the inflow speed which is in sharp contrast with the square law for a rigid body in a viscous flow
An IB Method for Non-Newtonian-Fluid Flexible-Structure Interactions in Three-Dimensions
Problems involving fluid flexible-structure interactions (FFSI) are ubiquitous in engineering and sciences. Peskin’s immersed boundary (IB) method is the first framework for modeling and simulation of such problems. This paper addresses a three-dimensional extension of the IB framework for non-Newtonian fluids which include power-law fluid, Oldroyd-B fluid, and FENE-P fluid. The motion of the non-Newtonian fluids are modelled by the lattice Boltzmann equations (D3Q19 model). The differential constitutive equations of Oldroyd-B and FENE-P fluids are solved by the D3Q7 model. Numerical results indicate that the new method is first-order accurate and conditionally stable. To show the capability of the new method, it is tested on three FFSI toy problems: a power-law fluid past a flexible sheet fixed at its midline, a flexible sheet being flapped periodically at its midline in an Oldroyd-B fluid, and a flexible sheet being rotated at one edge in a FENE-P fluid
A stress tensor discontinuity-based immersed boundary-lattice Boltzmann method
We propose an immersed boundary-lattice Boltzmann method using the discontinuity of the stress tensor. In the immersed boundary method, the body force which is applied to enforce the no-slip boundary condition is equivalent to the discontinuity of the stress tensor across the boundary. In the proposed method, the boundary is expressed by Lagrangian points independently of the background lattice points, and the discontinuity of the stress tensor is calculated on these points from desired particle distribution functions which satisfy the no-slip boundary condition based on the bounce-back scheme. By using this method, we can obtain the force locally acting on the boundary from the stress tensor of one side of the fluids divided by the boundary, and there is no need to consider the internal mass effect in calculating the total force and torque acting on the boundary. To our best knowledge, the present method is the first one which enables us to calculate the stress tensor on the boundary in the class of the diffusive interface method. In order to validate the present method, we apply it to simulations of typical moving-boundary problems, i.e., a Taylor-Couette flow, an oscillating circular cylinder in a stationary fluid, the sedimentation of an elliptical cylinder, and the sedimentation of a sphere. As a result, the present method has the first-order spatial accuracy and has a good agreement with other numerical and experimental results. In addition, we discuss two problems of the present method, i.e., penetration and spurious oscillation of local force, and a possible remedy for them. (C) 2018 Elsevier Ltd. All rights reserved.ArticleCOMPUTERS & FLUIDS.172: 593-608(2018)journal articl
Inertial Coupling Method for particles in an incompressible fluctuating fluid
We develop an inertial coupling method for modeling the dynamics of
point-like 'blob' particles immersed in an incompressible fluid, generalizing
previous work for compressible fluids. The coupling consistently includes
excess (positive or negative) inertia of the particles relative to the
displaced fluid, and accounts for thermal fluctuations in the fluid momentum
equation. The coupling between the fluid and the blob is based on a no-slip
constraint equating the particle velocity with the local average of the fluid
velocity, and conserves momentum and energy. We demonstrate that the
formulation obeys a fluctuation-dissipation balance, owing to the
non-dissipative nature of the no-slip coupling. We develop a spatio-temporal
discretization that preserves, as best as possible, these properties of the
continuum formulation. In the spatial discretization, the local averaging and
spreading operations are accomplished using compact kernels commonly used in
immersed boundary methods. We find that the special properties of these kernels
make the discrete blob a particle with surprisingly physically-consistent
volume, mass, and hydrodynamic properties. We develop a second-order
semi-implicit temporal integrator that maintains discrete
fluctuation-dissipation balance, and is not limited in stability by viscosity.
Furthermore, the temporal scheme requires only constant-coefficient Poisson and
Helmholtz linear solvers, enabling a very efficient and simple FFT-based
implementation on GPUs. We numerically investigate the performance of the
method on several standard test problems...Comment: Contains a number of corrections and an additional Figure 7 (and
associated discussion) relative to published versio
A Review on Contact and Collision Methods for Multi-body Hydrodynamic problems in Complex Flows
Modeling and direct numerical simulation of particle-laden flows have a
tremendous variety of applications in science and engineering across a vast
spectrum of scales from pollution dispersion in the atmosphere, to fluidization
in the combustion process, to aerosol deposition in spray medication, along
with many others. Due to their strongly nonlinear and multiscale nature, the
above complex phenomena still raise a very steep challenge to the most
computational methods. In this review, we provide comprehensive coverage of
multibody hydrodynamic (MBH) problems focusing on particulate suspensions in
complex fluidic systems that have been simulated using hybrid
Eulerian-Lagrangian particulate flow models. Among these hybrid models, the
Immersed Boundary-Lattice Boltzmann Method (IB-LBM) provides mathematically
simple and computationally-efficient algorithms for solid-fluid hydrodynamic
interactions in MBH simulations. This paper elaborates on the mathematical
framework, applicability, and limitations of various 'simple to complex'
representations of close-contact interparticle interactions and collision
methods, including short-range inter-particle and particle-wall steric
interactions, spring and lubrication forces, normal and oblique collisions, and
mesoscale molecular models for deformable particle collisions based on
hard-sphere and soft-sphere models in MBH models to simulate settling or flow
of nonuniform particles of different geometric shapes and sizes in diverse
fluidic systems.Comment: 37 pages, 12 Figure
PIBM: Particulate immersed boundary method for fluid-particle interaction problems
It is well known that the number of particles should be scaled up to enable industrial scale simulation. The calculations are more computationally intensive when the motion of the surrounding fluid is considered. Besides the advances in computer hardware and numerical algorithms, the coupling scheme also plays an important role on the computational efficiency. In this study, a particulate immersed boundary method (PIBM) for simulating the fluid–particle multiphase flow was presented and assessed in both two- and three-dimensional applications. The idea behind PIBM derives from the conventional momentum exchange-based Immersed Boundary Method (IBM) by treating each Lagrangian point as a solid particle. This treatment enables Lattice Boltzmann Method (LBM) to be coupled with fine particles residing within a particular grid cell. Compared with the conventional IBM, dozens of times speedup in two-dimensional simulation and hundreds of times in three-dimensional simulation can be expected under the same particle and mesh number. Numerical simulations of particle sedimentation in Newtonian flows were conducted based on a combined LBM–PIBM–Discrete Element Method (DEM) scheme, showing that the PIBM can capture the feature of particulate flows in fluid and is indeed a promising scheme for the solution of the fluid–particle interaction problems
PIBM: Particulate immersed boundary method for fluid-particle interaction problems
It is well known that the number of particles should be scaled up to enable industrial scale simulation. The calculations are more computationally intensive when the motion of the surrounding fluid is considered. Besides the advances in computer hardware and numerical algorithms, the coupling scheme also plays an important role on the computational efficiency. In this study, a particulate immersed boundary method (PIBM) for simulating the fluid–particle multiphase flow was presented and assessed in both two- and three-dimensional applications. The idea behind PIBM derives from the conventional momentum exchange-based Immersed Boundary Method (IBM) by treating each Lagrangian point as a solid particle. This treatment enables Lattice Boltzmann Method (LBM) to be coupled with fine particles residing within a particular grid cell. Compared with the conventional IBM, dozens of times speedup in two-dimensional simulation and hundreds of times in three-dimensional simulation can be expected under the same particle and mesh number. Numerical simulations of particle sedimentation in Newtonian flows were conducted based on a combined LBM–PIBM–Discrete Element Method (DEM) scheme, showing that the PIBM can capture the feature of particulate flows in fluid and is indeed a promising scheme for the solution of the fluid–particle interaction problems
Interactive 3D simulation for fluid–structure interactions using dual coupled GPUs
The scope of this work involves the integration of high-speed parallel computation with interactive, 3D visualization of the lattice-Boltzmann-based immersed boundary method for fluid–structure interaction. An NVIDIA Tesla K40c is used for the computations, while an NVIDIA Quadro K5000 is used for 3D vector field visualization. The simulation can be paused at any time step so that the vector field can be explored. The density and placement of streamlines and glyphs are adjustable by the user, while panning and zooming is controlled by the mouse. The simulation can then be resumed. Unlike most scientific applications in computational fluid dynamics where visualization is performed after the computations, our software allows for real-time visualizations of the flow fields while the computations take place. To the best of our knowledge, such a tool on GPUs for FSI does not exist. Our software can facilitate debugging, enable observation of detailed local fields of flow and deformation while computing, and expedite identification of ‘correct’ parameter combinations in parametric studies for new phenomenon. Therefore, our software is expected to shorten the ‘time to solution’ process and expedite the scientific discoveries via scientific computing
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