scholarly journals Lattice Boltzmann simulation of low-Reynolds-number cavitating contracting-nozzle flow interacting with a moving valve

AIP Advances ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 125203
Author(s):  
Tianpei Luo ◽  
Jun Xia
Keyword(s):  
Reynolds Number ◽  
Lattice Boltzmann ◽  
Low Reynolds Number ◽  
Nozzle Flow ◽  
Lattice Boltzmann Simulation ◽  
Low Reynolds

scholarly journals Lattice Boltzmann simulations of low-Reynolds-number flows past fluidized spheres: effect of inhomogeneities on the drag force

2017 ◽  
Vol 833 ◽  
pp. 599-630 ◽  
Author(s):  
Gregory J. Rubinstein ◽  
Ali Ozel ◽  
Xiaolong Yin ◽  
J. J. Derksen ◽  
Sankaran Sundaresan
Keyword(s):  
Reynolds Number ◽  
Drag Force ◽  
Lattice Boltzmann ◽  
Volume Fraction ◽  
Low Reynolds Number ◽  
Particle Volume Fraction ◽  
Spherical Particles ◽  
Particle Volume ◽  
Lattice Boltzmann Simulations ◽  
Low Reynolds

The formation of inhomogeneities within fluidized beds, both in terms of the particle configurations and flow structures, have a pronounced effect on the interaction force between the fluid and particles. While recent numerical studies have begun to probe the effects of inhomogeneities on the drag force at the particle scale, the applicability of prior microscale constitutive drag relations is still limited to random, homogeneous distributions of particles. Since an accurate model for the drag force is needed to predict the fluidization behaviour, the current study utilizes the lessons of prior inhomogeneity studies in order to derive a robust drag relation that is both able to account for the effect of inhomogeneities and applicable as a constitutive closure to larger-scale fluidization simulations. Using fully resolved lattice Boltzmann simulations of systems composed of fluid and monodisperse spherical particles in the low-Reynolds-number (Re) regime, the fluid–particle drag force, normalized by the ideal Stokes drag force, is found to significantly decrease, over a range of length scales, as the extent of inhomogeneities increases. The extent of inhomogeneities is found to most effectively be quantified through one of two subgrid-scale quantities: the scalar variance of the particle volume fraction or the drift flux, which is the correlation between the particle volume fraction and slip velocity. Scale-similar models are developed to estimate these two subgrid measures over a wide range of system properties. Two new drag constitutive models are proposed that are not only functions of the particle volume fraction and the Stokes number ($St$), but also dependent on one of these subgrid measures for the extent of inhomogeneities. Based on the observed, appreciable effect of inhomogeneities on drag, these new low-Re drag models represent a significant advancement over prior constitutive relations.

Determining Flow Mixing Characteristics in Low Reynolds Numbers Micro Wavy Channels by the Lattice-Boltzmann Method

2010 ◽  
Author(s):  
Amador M. Guzma´n ◽  
Mari´a Gabriela Quezada ◽  
Luis E. Sanhueza ◽  
Andre´s J. Di´az
Keyword(s):  
Reynolds Number ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Low Reynolds Number ◽  
Mixing Enhancement ◽  
Flow Mixing ◽  
Mixing Characteristics ◽  
Low Reynolds ◽  
Wavy Channels ◽  
Boltzmann Method

The Eulerian and Lagrangian flow mixing characteristics in a two-dimensional (2D) micro wavy channels for low Reynolds number have been investigated using the Lattice-Boltzmann method (LBM) for solving the governing Boltzmann Transport Equation (BTE). Numerical simulations of a Newtonian compressible flow for Reynolds number flow regimes lower than Re = 0.505 are performed using a computational model of a symmetric wavy channel with many cavities and a geometrical aspect ratio of r = a/(2L) = 0.375, where a is the amplitude of the sinusoidal wall, and L is the cavity periodic length. The Eulerian flow characteristics are determined for different Knudsen numbers with the objective of characterizing time dependent velocity and flow patterns. Then, the Lagrangian characteristics are obtained by integrating the Eulerian velocity field. Thousands of massless fluid particles are used for determining fluid particle Lagrangian trajectories, stretching fields and Lagrangian Lyapunov exponents associated to possible evidences of flow mixing enhancement in different regions of the micro channel. The numerical results demonstrate that low Reynolds number compressible flows in micro wavy channels develop Lagrangian characteristics and stretching field that can lead later to flow mixing enhancement characteristics in an electroosmotic flow in microchannels with wavy, grooved and/or any other surface pattering on the channels walls.

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