Lattice Boltzmann Computations of the Fluid Flow in the Wake of a Wind Turbine Modelled by a Porous Disk Lattice Boltzmann Computations of the Fluid Flow in the Wake of a Wind Turbine Modelled by a Porous Disk

Fluid flow at nanoscopic scales is characterized by the dominance of thermal fluctuations (Brownian motion) versus directed motion. Thus, at variance with Lattice Boltzmann models for macroscopic flows, where statistical fluctuations had to be eliminated as a major cause of inefficiency, at the nanoscale they have to be summoned back. This Chapter illustrates the “nemesis of the fluctuations” and describe the way they have been inserted back within the LB formalism. The result is one of the most active sectors of current Lattice Boltzmann research.

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Effect of Slit Inclusions in Drag Reduction of Flow over Cylinders

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.846.18 ◽

2016 ◽

Vol 846 ◽

pp. 18-22

Author(s):

Rohit Bhattacharya ◽

Abouzar Moshfegh ◽

Ahmad Jabbarzadeh

Keyword(s):

Fluid Flow ◽

Drag Reduction ◽

Drag Coefficient ◽

Finite Volume ◽

Lattice Boltzmann ◽

Circular Cross Section ◽

Finite Volume Methods ◽

Turbulent Regime ◽

Ansys Fluent ◽

Comparison Of The Results

The flow over bluff bodies is separated compared to the flow over streamlined bodies. The investigation of the fluid flow over a cylinder with a streamwise slit has received little attention in the past, however there is some experimental evidence that show for turbulent regime it reduces the drag coefficient. This work helps in understanding the fluid flow over such cylinders in the laminar regime. As the width of the slit increases the drag coefficient keeps on reducing resulting in a narrower wake as compared to what is expected for flow over a cylinder. In this work we have used two different approaches in modelling a 2D flow for Re=10 to compare the results for CFD using finite volume method (ANSYS FLUENTTM) and Lattice Boltzmann methods. In all cases cylinders of circular cross section have been considered while slit width changing from 10% to 40% of the cylinder diameter. . It will be shown that drag coefficient decreases as the slit ratio increases. The effect of slit size on drag reduction is studied and discussed in detail in the paper. We have also made comparison of the results obtained from Lattice Boltzmann and finite volume methods.

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The Effects of Periodicity Assumptions in Porous Media Modelling

Transport in Porous Media ◽

10.1007/s11242-021-01587-1 ◽

2021 ◽

Author(s):

T. O. M. Forslund ◽

I. A. S. Larsson ◽

J. G. I. Hellström ◽

T. S. Lundström

Keyword(s):

Fluid Flow ◽

Lattice Boltzmann ◽

Single Unit ◽

Unsteady Flows ◽

Unit Cell ◽

Porous Bed ◽

Bed Porosity ◽

Macroscopic Properties ◽

Boltzmann Method ◽

Method Model

AbstractThe effects of periodicity assumptions on the macroscopic properties of packed porous beds are evaluated using a cascaded Lattice-Boltzmann method model. The porous bed is modelled as cubic and staggered packings of mono-radii circular obstructions where the bed porosity is varied by altering the circle radii. The results for the macroscopic properties are validated using previously published results. For unsteady flows, it is found that one unit cell is not enough to represent all structures of the fluid flow which substantially impacts the permeability and dispersive properties of the porous bed. In the steady region, a single unit cell is shown to accurately represent the fluid flow across all cases studied

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Fluid–Structure Interaction of High Aspect-Ratio Hair-Like Micro-Structures Through Dimensional Transformation Using Lattice Boltzmann Method

International Journal of Applied Mechanics ◽

10.1142/s1758825116500952 ◽

2016 ◽

Vol 08 (08) ◽

pp. 1650095 ◽

Cited By ~ 2

Author(s):

H. Devaraj ◽

Kean C. Aw ◽

E. Haemmerle ◽

R. Sharma

Keyword(s):

Fluid Flow ◽

Drag Force ◽

Lattice Boltzmann ◽

Stokes Equations ◽

Fluid Structure Interaction ◽

Structural Response ◽

Momentum Exchange ◽

Fluid Structure ◽

Structure Interaction ◽

Micro Structures

3D printed hair-like micro-structures have been previously demonstrated in a novel micro-fluidic flow sensor aimed at sensing air flows down to rates of a few milliliters per second. However, there is a lack of in-depth understanding of the structural response of these ‘micro-hairs' under a fluid flow field. This paper demonstrates the use of lattice Boltzmann methods (LBM) to understand this structural response towards a better optimization of the micro-hair flow sensors designed to suit the end applications' needs. The LBM approach was chosen as an efficient alternative to simulate Navier–Stokes equations for modeling fluid flow around complex geometries primarily for improved accuracy and simplicity with lesser computational costs. As the spatial dimensions of the sensor's flow channel are much larger in comparison to the actual micro-hairs (the sensing element), a multidimensional approach of combining two-dimensional (D2Q9) and three-dimensional (D3Q19) lattice configurations were implemented for improved computational speeds and efficiency. The drag force on the micro-hairs was estimated using the momentum-exchange method in the D3Q19 configuration and this drag force is transferred to the structural analysis model which determines the micro-hair deformation using Euler–Bernoulli beam theory. The entirety of the LBM Fluid–Structure Interaction (FSI) model was implemented within MATLAB and the obtained results are compared against the numerical model implemented on a commercially available software package.

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