Lattice Boltzmann Numerical Prediction of Flow Behavior Downstream of Cylinder Blockage at Various Reynolds Numbers (original) (raw)
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Lattice Boltzmann simulation of flow over a circular cylinder at moderate Reynolds numbers
Thermal Science, 2014
This work is concerned with Lattice Boltzmann computation of two-dimensional incompressible viscous flow past a circular cylinder confined in a channel. Computations are carried out both for steady and unsteady flows and the critical Reynolds number at which symmetry breaks and unsteadiness sets in is predicted. Effects of Reynolds number, blockage ratio and channel length are studied in some details. All the results compare quite well with those computed with continuum-based methods, demonstrating the ability and usefulness of the Lattice Boltzmann Method (LBM) in capturing the flow features of this interesting and fluid-mechanically rich problem.
Numerical Simulation of Viscous Flow over a Square Cylinder Using Lattice Boltzmann Method
ISRN Mathematical Physics, 2012
This work is concerned with the lattice Boltzmann computation of two-dimensional incompressible viscous flow past a square cylinder confined in a channel. It is known that the nature of the flow past cylindrical obstacles is very complex. In the present work, computations are carried out both for steady and unsteady flows using lattice Boltzmann method. Effects of Reynolds number, blockage ratio, and channel length are studied in detail. As good care has been taken to include appropriate measures in the computational method, these results enjoy good credibility. To sum up, the present study reveals many interesting features of square cylinder problem and demonstrates the capability of the lattice Boltzmann method to capture these features.
Entropic Lattice Boltzmann Simulation of the Flow Past Square Cylinder
International Journal of Modern Physics C, 2004
Minimal Boltzmann kinetic models, such as lattice Boltzmann, are often used as an alternative to the discretization of the Navier-Stokes equations for hydrodynamic simulations. Recently, it was argued that modeling sub-grid scale phenomena at the kinetic level might provide an efficient tool for large scale simulations. Indeed, a particular variant of this approach, known as the entropic lattice Boltzmann method (ELBM), has shown that an efficient coarse-grained simulation of decaying turbulence is possible using these approaches. The present work investigates the efficiency of the entropic lattice Boltzmann in describing flows of engineering interest. In order to do so, we have chosen the flow past a square cylinder, which is a simple model of such flows. We will show that ELBM can quantitatively capture the variation of vortex shedding frequency as a function of Reynolds number in the low as well as the high Reynolds number regime, without any need for explicit sub-grid scale modeling. This extends the previous studies for this set-up, where experimental behavior ranging from Re ∼ O(10) to Re ≤ 1000 was predicted by a single simulation algorithm. 1-5
2014
Numerical calculations of flow around a square cylinder are presented using the multi-relaxation-time lattice Boltzmann method at Reynolds number 150. The effects of upstream locations, downstream locations and blockage are investigated systematically. A detail analysis are given in terms of time-trace analysis of drag and lift coefficients, power spectra analysis of lift coefficient, vorticity contours visualizations and phase diagrams. A number of physical quantities mean drag coefficient, drag coefficient, Strouhal number and root-mean-square values of drag and lift coefficients are calculated and compared with the well resolved experimental data and numerical results available in open literature. The results had shown that the upstream, downstream and height of the computational domain are at least 7.5, 37.5 and 12 diameters of the cylinder, respectively.
A lattice Boltzmann study of 2D steady and unsteady flows around a confined cylinder
Journal of The Brazilian Society of Mechanical Sciences and Engineering, 2020
In this work, the lattice Boltzmann (LB) method was applied to simulate incompressible steady and unsteady low Reynolds number (Re) flows around a confined cylinder. In the LB method, different collision models (Bhatnagar-Gross-Krook model, two-relaxation-time model, multi-relaxation-time model, and entropic lattice Boltzmann model) and a regularization model were used, and the results were compared. Numerical results pertaining to a two-dimensional flow around a cylinder are reported and compared with numerical and experimental data available in the literature. The results agree with the predictions made from the literature. A correlation for Strouhal number (St) for 55 ≤ Re ≤ 300 is suggested.
A two-dimensional lattice Boltzmann study of flow past five side-by-side rectangular cylinders
Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2018
Numerical simulations are performed, in the range of 0.5 B g B 5, where g is the separation ratio between the cylinders at fixed Reynolds number 150 and aspect ratio 2, for flow past five side-by-side rectangular cylinders. A two-dimensional code is developed using the lattice Boltzmann method. The effect of separation ratio on the vortex shedding frequency, time-trace analysis of drag and lift coefficients, power spectra analysis of lift coefficients and force statistics exerted on the cylinders is quantified together with the observed flow structure. Five different flow structures were found and named as nearly symmetric (g = 0.5), flip-flopping (g = 1), modulated (g = 1.5), strongly interactive (g = 2, 2.5 and 3) and weakly interactive (g = 4 and 5) flow structures. It is found that the vortices are generated on the surfaces of the cylinders as width of the cylinder is 2h (h is the width of the rectangular cylinders) and due to this there is modulation in time-history analysis of drag and lift coefficients for all chosen cases except at g = 0.5. The Strouhal number is also calculated using Welch's method for comparison, and correlation of lift coefficients for different combinations is also given.
Lattice Boltzmann Method to Analyse Fluid Flow Around a Circular Cylinder
2019
An overview of the Lattice Boltzmann Method has been presented with an in house algorithm for the numerical simulation of fluid flow around a circular cylinder. The linearization of the collision operator has been discussed for distributions not close to the local equilibrium state, and numerical simulation has been carried out for stable initial conditions up to a Reynolds number of 80. An overview of the lattice gas automata with regard to Boolean variables describing the particle occupation has also been defined. A comparison between the data obtained from the two dimensional fluid flow around the cylinder and previous experimentation has also been made.
2015
In this research numerical simulations are performed, using the multi-relaxation-time lattice Boltzmann method, in the range 3 ≤ β = w[d] ≤ 30 at Re = 100, 200 and 300, where β the blockage ratio, w is the equispaced distance between centers of cylinders, d is the diameter of the cylinder and Re is the Reynolds number, respectively. Special attention is paid to the effect of the equispaced distance between centers of cylinders. Visualization of the vorticity contour visualization are presented for some simulation showing the flow dynamics and patterns for blockage effect. Results show that the drag and mean drag coefficients, and Strouhal number, in general, decrease with the increase of β for fixed Re. It is found that the decreasing rate of drag and mean drag coefficients and Strouhal number is more distinct in the range 3 ≤ β ≤ 15. We found that when β > 15, the blockage effect almost diminishes. Our results further indicate that the drag and mean drag coefficients, peak value...
Computers & Fluids, 2006
The low-Reynolds number flow around two square cylinders placed side-by-side is investigated using the lattice Boltzmann method (LBM). The effects of the gap ratio s/d (s is the separation between the cylinders and d is the characteristic dimension) on the flow are studied. These simulations reveal the existence of regimes with either synchronized or non-synchronized vortex-shedding, with transition occurring at s/d % 2, which is larger than for circular cylinders. Detailed results are presented at Re = 73 for s/d = 2.5 and 0.7 corresponding to the synchronized and flip-flop regimes, respectively. Vortex-shedding from the cylinder occurs either in-phase or in-antiphase in the synchronized regime. However, linear stochastic estimate (LSE) calculations show that inphase locking is the predominant mode. LSE is also employed to educe the underlying modes in the flip-flop regime, where evidence for both in-phase and anti-phase locked vortices is found, indicating that this regime is in a quasi-stable state between these two modes. The merging of the wakes, which is gradual for the synchronized regime, occurs rapidly in the flip-flop regime. The mean pressure on the upstream surface is symmetric and asymmetric for the synchronized and flip-flop regimes, respectively. Differences in results between the two regimes are interpreted in terms of the interaction of the jet formed between the cylinders with the adjoining wakes, the strength of this interaction depending on the spacing.