Bulletin of the American Physical Society
74th Annual Meeting of the APS Division of Fluid Dynamics
Volume 66, Number 17
Sunday–Tuesday, November 21–23, 2021; Phoenix Convention Center, Phoenix, Arizona
Session M17: Computational Fluid Dynamics: Applications II; LBM |
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Chair: Cristopher Rycroft, Harvard Room: North 131 AB |
Monday, November 22, 2021 1:10PM - 1:23PM |
M17.00001: 1-D and 3-D Computational Fluid Dynamics Model Comparison of the Treatment Performance of a Full-scale Oxidation Ditch Kiesha C Pierre, Andres E Tejada-Martinez, Tolga Pirasaci, Anthony Perez, Aydin Sunol Modeling an oxidation ditch with computational fluid dynamics (CFD) can be computationally expensive. While, a one-dimensional (1-D) model can reduce the expense, there could be a significant tradeoff in solution accuracy. This research sought to address how well a 1-D model can approximate the treatment performance of a 3-D model of a full-scale oxidation ditch. Both models incorporated bio-kinetics via the Activated Sludge Model (ASM)-1, to predict the treatment performance of the ditch based on the concentration of the ASM-1 components. When comparing the time-series of the concentration of ASM-1 components averaged over the ditch for 40 days, both 1-D and 3-D models displayed similar trends with slight differences in steady state values, except for soluble nitrate nitrite nitrogen (SNO). The steady state value of SNO was greater by more than 150% for the 1-D model than the 3-D model. This difference was attributed to heterogeneities in dissolved oxygen concentration predicted in the 3D model that were not captured by the 1-D model, leading the latter to under-predict the denitrification process. Additionally, the spiraling flow around the aerators that play an important role in determining the spatial distribution of dissolved oxygen cannot be represented in the 1-D model. |
Monday, November 22, 2021 1:23PM - 1:36PM |
M17.00002: Numerical Analysis on the Full Phase Flow Dynamics of Covid-19 Droplets Transmission Rajendra Shrestha, Juanpablo Delgado, Michael P Kinzel The perpetual nature of the human economic world was shattered with the sudden spread out of the Covid-19. The Covid-19 virus that was first detected in the Wuhan city of China didn’t take long to reach every corner of the world, mostly due to its contagious nature. Viruses are transmitted in the form of droplets (aerosol) released during speaking, sneezing, and coughing. The full phase flow dynamics of a human speaking, sneezing, and coughing behaviors have been studied applying the Computational Fluid Dynamics (CFD) tool called Star CCM+. In this CFD model, the multiphase Lagrangian droplets of various sizes were released with a sinusoidal velocity, from the buccal cavity of a human mouth into the Eulerian multiphase room atmosphere. The amount of the droplets at the distances away from the human mouth were quantified for each phenomenon of speaking, sneezing, and coughing, with a mask and without a mask. The results show the ability of the mask to reduce droplet transmission. In the next part, this research established a transfer function that relates the amount of droplet particles of various sizes with the distances away from the source. The experimental facility has limited ability to quantify the amount of droplet particles (for a given particular size) at the distances away from the source, except exactly at the source. Using the CFD results, the transfer function proposed is enabled to provide missing information for the experimental results. |
Monday, November 22, 2021 1:36PM - 1:49PM |
M17.00003: A fully Eulerian lattice Boltzmann simulation of multi-soft-body fluid–structure interaction Yue Sun, Christopher Rycroft We introduce a new Eulerian simulation method for simulating a fluid interacting with finite-strain deformable solids. The fluid is simulated using the lattice Boltzmann (LB) method on a fixed grid, and the solids use the reference map technique (RMT) that allows finite-strain elasticity to be modeled using the same grid as the fluid. By using a unified grid for both the fluid and solid phases, the interphase coupling is greatly simplified. The new hybrid simulation method, the LBRMT, inherits the attractive features of the LB method to simulate a quasi-incompressible fluid in a simple and parallelized fashion. Since our hybrid method only has one global velocity field, it is well-suited for modeling complex geometries and multi-body contact. We demonstrate our method with examples of many deformable solids sedimenting and floating, bending and twisting of flexible rotors, and collective motion of actuated microswimmers. |
Monday, November 22, 2021 1:49PM - 2:02PM |
M17.00004: Image-based Computational Hemodynamics for Endothelium Shear Stress in Human Choriocapillaris Using Volumetric Lattice Boltzmann Method Huidan Yu, Senyou An, Islam M Mahfuzul, Xiaoyu Zhang, Bradley D Gelfand Disorders of the choroidal circulation are an etiologic element of age-related macular degeneration (AMD), affecting an estimated 2.5% of the world’s population, and causes blindness in millions of people. Endothelium shear stress (ESS) experienced by choroidal endothelial cells in health or disease has been suspected of contributing to physiology and pathophysiology of AMD, but it has never been studied in a anatomically realistic manner. Consequently, the biologic and pathologic effects of choroidal ESS are not known owing to the lack of appropriate research means. We present a unique and powerful computational platform, called InVascular, that enables quantification of ESS, in three-dimensional human choroidal vasculature networks derived from human cadaver eyes using kinetic-based lattice Boltzmann method. The choroidal vasclarture is reconstructed from high-resolution confocal microscopy staining of an human donor eyes. The anatomic segmentation of the inner choroidal vasculature, together with the pressure conditions at the arterioles and venules, is fed into InVascular to quantify the choridal hemodynamics. GPU-accelerated InVascular is highly computational efficient, enabling the study a large number of samples. Validation of InVascular against a state-of-the-art analytical model that uses an idealized geometry for choroicapillaries achieved excellent agreement in qualitative and quantitative metrics of blood flow. InVascular is expected to unveil changes in the distribution of ESS in heatlhy and diseased eyes. Insights gleaned from these studies could stimulate development of new prognostic analyses, such as ‘hemodynamic risk assessments’ to identify regions of the eye that are disease susceptible, or to stratify patients for enrollment in clinical trials. |
Monday, November 22, 2021 2:02PM - 2:15PM |
M17.00005: Numerical and Experimental Studies of Industrial Internal Flows: Application to Ultrasonic Flow Meters Mario J Rincón, Martino Reclari, Mahdi Abkar Ultrasonic flow meters present an interesting industrial internal-flow problem due to their unique geometry and complex interaction of fluid flow with sound waves. In this study, Computational Fluid Dynamics (CFD) with the Finite Volume Method (FVM) of the general-purpose solver, OpenFOAM, is used to predict the turbulent flow field inside a flow meter. Different levels of fidelity from CFD RANS to LES with various turbulence and subgrid-scale (SGS) models are evaluated and compared with Particle Image Velocimetry (PIV) measurements in both qualitative and quantitative manners. The evaluation shows the discrepancies of each method and its computational cost, providing a robust and time-efficient framework to analyse internal-flow problems with similar features. |
Monday, November 22, 2021 2:15PM - 2:28PM |
M17.00006: Direct numerical simulations of laminar droplet breakup in static mixers under different inlet conditions Juan Pablo Valdes, Lyes Kahouadji, Fuyue Liang, Seungwon Shin, Jalel Chergui, Damir Juric, Omar K Matar The effect of different inlet dispersed phase morphologies on the mechanics underlying droplet deformation and breakage across a standard SMX static mixer is studied. Three conditions are considered whereby the dispersed phase fraction is simultaneously varied to account for the influence of coalescence events: 1) negligible coalescence, three individual droplets mimicking a controlled syringe injection; 2) low dispersed phase fraction, numerous variable-sized droplets simulating a pre-mixed inlet; and 3) intermediate dispersed phase fraction, jet inlet emulating a standard phase injection from a gear pump. This study implements massively-parallel high-fidelity three-dimensional direct numerical simulations with a hybrid front-tracking level-set interface capturing algorithm. Governing forces and prevaling deformation/breakup mechanisms are identified for each inlet condition based on literature models. Some of these include 3D elongation and rupture at cross-points driven by buoyancy forces, or droplet adherence to an interstice, growth, and posterior detachment as smaller drops driven mostly by viscous and frictional forces. These mechanisms are elucidated by the strain rate and maximum stretching efficiency profiles across the mixer. |
Monday, November 22, 2021 2:28PM - 2:41PM |
M17.00007: A quantitative comparison of physical accuracy and numerical stability of Lattice Boltzmann color gradient and pseudopotential multicomponent models for the jetting of microdroplets Karun Datadien, Gianluca Di Staso, Herman Wijshoff, Federico Toschi The performances of the Color-Gradient (CG) and of the Shan-Chen (SC) multicomponent Lattice Boltzmann models are quantitatively compared side-by-side on multiple physical flow problems where breakup, coalescence and contraction of fluid ligaments are important. These include flow problems relevant to microfluidic applications, such as the jetting of microdroplets as seen in inkjet printing. Specifically we consider droplet oscillation, ligament contraction and Rayleigh-Plateau instability simulations. One to one comparisons between CG and SC are made to compare their performance. Our results show that the CG model is a suitable choice for challenging simulations of droplet formation, due to numerical stability, physical accuracy and wide range of accessible parameters. A realistic jetting simulation with typical fluid parameters found in industrial applications is shown to be achievable using the Color-Gradient model. Specifically, the jetting simulation features tunable nozzle wetting boundary conditions and a high ink-air density ratio of 1000 at a capillary number, Ca = 1.61, determined by the surface tension, viscosity and jetting velocity of the ink. |
Monday, November 22, 2021 2:41PM - 2:54PM |
M17.00008: Fluid Dynamic performance of Euplectella aspergillum: drawing inspiration from deep-sea glass sponges for engineering design Giacomo Falcucci, Giorgio Amati, Giovanni Polverino, Pierluigi Fanelli, Vesselin K Krastev, Maurizio Porfiri, Sauro Succi We analyze in detail the fluid dynamic performance of the deep-sea glass sponge Euplectella aspergillum through very large-scale simulations carried out on the Italian HPC facility of CINECA, “Marconi100”. |
Monday, November 22, 2021 2:54PM - 3:07PM |
M17.00009: Slip boundary conditions in lattice Boltzmann simulations: On-site stress-tensor-based formulation Adriano Grigolo, Julio Meneghini We propose a stress-tensor-based approach for fixing on-site hydrodynamic slip boundary conditions in lattice Boltzmann simulations. The formulation is presented in the framework of the widely employed D2Q9 lattice but it can be similarly applied to other lattice models. In our method, the slip length is a prescribed parameter and the Robin-type conditions to be enforced at an off-lattice wall point are transported to a wall-adjacent wet node and reinterpreted in terms of stress components. The resulting constraint equations at the wet node are solved by correcting inbound populations (whose reference values are given by the bounce-back rule) so that, along with the impermeable-wall condition, the desired relation between slip velocity and tangential stress is matched. The implementation is local and accounts for the effects of body forces, moving walls, and surface curvature; mass conservation is also ensured. Numerical tests reveal the scheme to be of satisfactory accuracy and it can therefore be regarded as a straightforward and easy-to-code alternative method for describing slippery boundaries in lattice Boltzmann simulations. |
Monday, November 22, 2021 3:07PM - 3:20PM |
M17.00010: The Onsager Regularized LBM Anirudh Jonnalagadda, Atul Sharma, Amit Agrawal The traditional single relaxation time (SRT) lattice Boltzmann method (LBM), namely the Lattice-BGK method (LBGK), demonstrates crippling physical and numerical defects that manifest as numerical instabilities in extreme flow conditions characterized by large Reynolds and Mach numbers. Although well established improvements to the LBGK models such as the Entropic LBM and Regularized LBM schemes address these issues, these methods are still characterized by subtle limitations such as the retention of spurious hydrodynamic moments in the case of the Entropic LBM and, an inherent inability to filter all non-hydrodynamic moments for every admissible lattice structure in the case of the state-of-the-art scheme among the Regularized LBMs. Here, we present a novel Regularized LBM scheme, named the Onsager-Regularized LBM (ORegularized LBM for brevity) which is derived from a phenomenological non-equilibrium thermodynamics perspective that is consistent with the Onsager Reciprocity Principle. The proposed method is extensively characterized for several canonical one- and two-dimensional benchmark flow problems and is found to significantly improve the stability regime over existing Regularized LBM schemes while also overcoming the limitations of the Entropic LBM methods.
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