Direct Simulation of Dense Suspensions of Non-Spherical Particles

2011 ◽  
Author(s):  
Orest Shardt ◽  
Jos Derksen
Keyword(s):  
Reynolds Number ◽  
Red Blood Cells ◽  
Sedimentation Rate ◽  
Immersed Boundary Method ◽  
Blood Cells ◽  
Volume Fraction ◽  
Immersed Boundary ◽  
Direct Simulation ◽  
Rigid Particles ◽  
Boundary Method

We describe the direct simulation of high-solids-fraction suspensions of non-spherical rigid particles that are slightly denser than the fluid. The lattice-Boltzmann method is used to solve the flow of the interstitial Newtonian fluid, and the immersed boundary method is used to enforce a no-slip boundary condition at the surface of each particle. The surface points for the immersed boundary method are also employed for collision handling by applying repulsive forces between nearby surface points. Due to the finite number of these points, the method simulates rough surface collisions. We also discuss methods for integrating the equations of particle motion at low density ratios and propose a method with improved accuracy. Rigid particles shaped like red blood cells were simulated. Simulations of a single particle showed that the particle settles in its original orientation when the Reynolds number is low (1.2) but flips to a higher drag orientation when the Reynolds number is higher (7.3). A simulation with a 45% solids volume fraction and a low solid over fluid density ratio showed the possibility of simulating blood as it is found in the body. A simulation at a lower solids volume fraction (35%) was used to compare the results with the erythrocyte sedimentation rate (ESR), a common blood test. The sedimentation rate was estimated as 0.2 mm/hr, which is an order of magnitude lower than a typical ESR of about 6 mm/hr for a healthy adult. The most likely reasons for the discrepancy are the omission of agglomeration-inducing inter-cellular forces from the simulations and the treatment of the red blood cells as rigid particles.

Direct Numerical Simulation of the Segre–Silberberg Effect Using Immersed Boundary Method

2020 ◽  
Vol 142 (11) ◽  
Author(s):  
Denis V. Esipov ◽  
Denis V. Chirkov ◽  
Dmitriy S. Kuranakov ◽  
Vasiliy N. Lapin
Keyword(s):  
Reynolds Number ◽  
Fluid Flow ◽  
Immersed Boundary Method ◽  
Particle Diameter ◽  
Practical Interest ◽  
Immersed Boundary ◽  
Rigid Particles ◽  
Boundary Method ◽  
Duct Geometry ◽  
Long Channel

Abstract One of the fundamental phenomena associated with the transport of rigid particles by the fluid flow in narrow ducts and tubes is the Segre–Silberberg effect. Experimental observations show that a spherical particle transported by the fluid flow in a long channel occupies a position of equilibrium between the wall and the centerline of the channel. In this study, this effect was numerically investigated using a novel semi-implicit immersed boundary method based on the discrete forcing approach. A uniform Cartesian mesh is used for the duct, whereas a moving Lagrangian mesh is used to track the position of the particle. Unlike previous studies, both cases of the duct geometry are considered: a round tube and a flat channel. Good agreement is shown to the available theoretical and numerical results of other studies. The problem is described by two dimensionless parameters, the channel Reynolds number, and the relative particle diameter. Parametric studies to these parameters were carried out, showing fundamental dependencies of equilibrium position on Reynolds number from 20 to 500 and on relative particle diameter from 0.2 to 0.7. It is demonstrated that the position of equilibrium becomes closer to the wall with the increase of Reynolds number, as well as with the decrease of particle diameter. In addition, the dependence of particle velocity on its diameter is investigated. The obtained results are of both theoretical and practical interest, with possible applications ranging from proppant transport to the design of microfluidic devices.

An Efficient Immersed Boundary Method Based on Penalized Direct Forcing for Simulating Flows Through Real Porous Media

2012 ◽  
Author(s):  
Wim-Paul Breugem ◽  
Vincent van Dijk ◽  
René Delfos
Keyword(s):  
Porous Medium ◽  
Ct Scan ◽  
Immersed Boundary Method ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Particle Diameter ◽  
Immersed Boundary ◽  
Average Particle ◽  
Boundary Method ◽  
Direct Forcing

A computationally efficient Immersed Boundary Method (IBM) based on penalized direct forcing was employed to determine the permeability of a real porous medium. The porous medium was composed of about 9000 glass beads with an average particle diameter of 1.93 mm and a porosity of 0.367. The forcing of the IBM depends on the local solid volume fraction within a computational grid cell. The latter could be obtained from a high-resolution X-ray Computed Tomography (CT) scan of the packing. An experimental facility was built to determine the permeability of the packing experimentally. Numerical simulations were performed for the same packing based on the data from the CT scan. For a scan resolution of 0.1 mm the numerical value for the permeability was nearly 70% larger than the experimental value. An error analysis indicated that the scan resolution of 0.1 mm was too coarse for this packing.

scholarly journals An Immersed Boundary Method Based on Volume Fraction

2015 ◽  
Vol 99 ◽  
pp. 677-685 ◽  
Author(s):  
Yuelong He ◽  
Dun Li ◽  
Shuai Liu ◽  
Handong Ma
Keyword(s):  
Immersed Boundary Method ◽  
Volume Fraction ◽  
Immersed Boundary ◽  
Boundary Method

Extra-Low Reynolds Number Vane Separation Using Immersed Boundary Method

2019 ◽  
Author(s):  
Prasert Prapamonthon ◽  
Bo Yin ◽  
Guowei Yang
Keyword(s):  
Reynolds Number ◽  
Gas Turbine ◽  
Immersed Boundary Method ◽  
Gas Turbines ◽  
Numerical Study ◽  
Flow Behavior ◽  
Immersed Boundary ◽  
Separation Flow ◽  
Boundary Method ◽  
Low Reynolds

Abstract Nowadays, mini unmanned aerial vehicles (MUAVs) and micro air vehicles (MAVs) are not only beneficially used as aviation models but also as modern drones for military missions and other civilian applications. Hence, research and development of propulsion sources for MUAVs and MAVs dynamically increase with a future trend of high performance, but low energy consumption. Certainly, using micro and ultra-small-size gas turbine is a good option for the propulsion source. To achieve ideal flight of MUAVs and MAVs powered by micro and ultra-small-size gas turbines under this trend, understanding of flow phenomena at wide ranges of Reynolds number is essential. This research presents a 2D numerical study of characteristics of laminar flow separation and the trailing-edge vortex on a turbine vane at extra-low Reynolds numbers (Res) i.e. Re = 1800 and 3600, and three rotational angles (α) i.e. α = 0°, 15° and 30° using immersed boundary method (IBM). With this method, the problem of incompressible flow is addressed by a sharp interface IBM. Numerical results indicate that IBM can characterize phenomena of laminar separation flow, which usually happens on the turbine airfoil when laminar boundary layer cannot overcome adverse pressure gradients and viscous effects. To our current knowledge, this may be the first research to study flow behavior at such low Res for gas turbine vanes using IBM. Even though it is now not common to operate micro and ultra-small-size gas turbines under these conditions, it is important to know how aerodynamic performance may be if micro and ultra-small-size gas turbines need to run under such conditions in the near future.

Numerical Simulation of Flow in a Wavy Wall Microchannel Using Immersed Boundary Method

2020 ◽  
Vol 13 (2) ◽  
pp. 118-125
Author(s):  
Mithun Kanchan ◽  
Ranjith Maniyeri
Keyword(s):  
Reynolds Number ◽  
Fluid Flow ◽  
Immersed Boundary Method ◽  
Stokes Equations ◽  
Flow Characteristics ◽  
Immersed Boundary ◽  
Solid Boundary ◽  
Wavy Wall ◽  
Dirac Delta ◽  
Boundary Method

Background: Fluid flow in microchannels is restricted to low Reynolds number regimes and hence inducing chaotic mixing in such devices is a major challenge. Over the years, the Immersed Boundary Method (IBM) has proved its ability in handling complex fluid-structure interaction problems. Objectives: Inspired by recent patents in microchannel mixing devices, we study passive mixing effects by performing two-dimensional numerical simulations of wavy wall in channel flow using IBM. Methods: The continuity and Navier-Stokes equations governing the flow are solved by fractional step based finite volume method on a staggered Cartesian grid system. Fluid variables are described by Eulerian coordinates and solid boundary by Lagrangian coordinates. A four-point Dirac delta function is used to couple both the coordinate variables. A momentum forcing term is added to the governing equation in order to impose the no-slip boundary condition between the wavy wall and fluid interface. Results: Parametric study is carried out to analyze the fluid flow characteristics by varying amplitude and wavelength of wavy wall configurations for different Reynolds number. Conclusion: Configurations of wavy wall microchannels having a higher amplitude and lower wavelengths show optimum results for mixing applications.

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