Complex Fluids and Flows: Algorithms and Applications

A special issue of Fluids (ISSN 2311-5521). This special issue belongs to the section "Non-Newtonian and Complex Fluids".

Deadline for manuscript submissions: closed (30 November 2021) | Viewed by 24404

Special Issue Editors


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Guest Editor
Department of Mechanical Engineering, University of Colorado Denver, CO 80204, USA
Interests: multiphase flows; turbulence; lattice Boltzmann methods for complex flows; thermal convective flows; non-Newtonian fluids; surface tension driven flow phenomena; kinetic theory; statistical mechanics of fluids
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Guest Editor
Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, St. Louis, MO 63130, USA
Interests: computational fluid dynamics (CFD); computational magnetohydrodynamics (MHD); electromagnetics; computational aeroacoustics; multidisciplinary design and optimization; rarefied gas dynamics and hypersonic flows, bio-fluid dynamics; flow and flight control
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Computational methods are at the heart of investigations in modern fluid dynamics, complementing theory and experimentation. They have become indispensable for simulations of complex fluids and flows, where features such as nonlinearity and/or nonlocality due to inertial effects or rheological constitutive equations, multiple scale effects, jumps in fluid properties across multi-fluid interfaces or non-continuum behavior pose significant challenges. In this Special Issue, we welcome papers that address the development and application of a variety of computational schemes for such problems, including the classical numerical techniques (finite difference, finite volume, finite element and spectral methods), mesoscopic methods including lattice Boltzmann methods, dissipative particle dynamics and other particle methods, as well as molecular dynamics. Our focus is on novel algorithms that simulate complex fluid motions efficiently and in a robust manner while delivering the required accuracy. Application areas include, but are not limited to, turbulence, non-Newtonian fluid flows, thermal convective flows, multiphase fluids, particulate systems, magnetohydrodynamic flows and microflows.

Dr. Kannan N. Premnath
Prof. Dr. Ramesh K. Agarwal
Guest Editors

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Keywords

  • complex fluids and flows
  • computational schemes
  • classical numerical techniques
  • mesoscopic methods
  • turbulence
  • non-Newtonian fluid flows
  • thermal convective flows
  • multiphase fluids, particulate systems
  • magnetohydrodynamic flows
  • microflows

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Published Papers (9 papers)

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Research

22 pages, 2190 KiB  
Article
Recent Upgrades in a 2D Turbulent Transport Solver Based on a Hybrid Discontinuous Galerkin Method for the Simulation of Fusion Plasma in Tokamak
by Giacomo Piraccini, Marcello Capasso, Manuel Scotto D’Abusco, Giorgio Giorgiani, Frédéric Schwander, Eric Serre, Hugo Bufferand, Guido Ciraolo and Patrick Tamain
Fluids 2022, 7(2), 63; https://doi.org/10.3390/fluids7020063 - 2 Feb 2022
Viewed by 1951
Abstract
The simulation of fusion plasmas in realistic magnetic configurations and tokamak geometries still requires the development of advanced numerical algorithms owing to the complexity of the problem. In this context, we propose a Hybrid Discontinuous Galerkin (HDG) method to solve 2D transport fluid [...] Read more.
The simulation of fusion plasmas in realistic magnetic configurations and tokamak geometries still requires the development of advanced numerical algorithms owing to the complexity of the problem. In this context, we propose a Hybrid Discontinuous Galerkin (HDG) method to solve 2D transport fluid equations in realistic magnetic and tokamak wall geometries. This high-order solver can handle magnetic equilibrium free structured and unstructured meshes allowing a much more accurate discretization of the plasma facing components than current solvers based on magnetic field aligned methods associated with finite-differences (volumes) discretization. In addition, the method allows for handling realistic magnetic equilibrium, eventually non steady, a critical point in the modeling of full discharges including ramp up and ramp down phases. In this paper, we introduce the HDG algorithm with a special focus on recent developments related to the treatment of the cross-field diffusive terms, and to an adaptive mesh refinement technique improving the numerical efficiency and robustness of the scheme. The updated solver is verified with a manufactured solution method, and numerical tests are provided to illustrate the new capabilities of the code. Full article
(This article belongs to the Special Issue Complex Fluids and Flows: Algorithms and Applications)
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24 pages, 4586 KiB  
Article
Analysis of the Shear-Thinning Viscosity Behavior of the Johnson–Segalman Viscoelastic Fluids
by Tomáš Bodnár and Adélia Sequeira
Fluids 2022, 7(1), 36; https://doi.org/10.3390/fluids7010036 - 14 Jan 2022
Cited by 7 | Viewed by 2657
Abstract
This paper presents a numerical comparison of viscoelastic shear-thinning fluid flow using a generalized Oldroyd-B model and Johnson–Segalman model under various settings. Results for the standard shear-thinning generalization of Oldroyd-B model are used as a reference for comparison with those obtained for the [...] Read more.
This paper presents a numerical comparison of viscoelastic shear-thinning fluid flow using a generalized Oldroyd-B model and Johnson–Segalman model under various settings. Results for the standard shear-thinning generalization of Oldroyd-B model are used as a reference for comparison with those obtained for the same flow cases using Johnson–Segalman model that has specific adjustment of convected derivative to assure shear-thinning behavior. The modeling strategy is first briefly described, pointing out the main differences between the generalized Oldroyd-B model (using the Cross model for shear-thinning viscosity) and the Johnson–Segalman model operating in shear-thinning regime. Then, both models are used for blood flow simulation in an idealized stenosed axisymmetric vessel under different flow rates for various model parameters. The simulations are performed using an in-house numerical code based on finite-volume discretization. The obtained results are mutually compared and discussed in detail, focusing on the qualitative assessment of the most distinct flow field differences. It is shown that despite all models sharing the same asymptotic viscosities, the behavior of the Johnson–Segalman model can be (depending on flow regime) quite different from the predictions of the generalized Oldroyd-B model. Full article
(This article belongs to the Special Issue Complex Fluids and Flows: Algorithms and Applications)
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48 pages, 7282 KiB  
Article
Three-Dimensional Central Moment Lattice Boltzmann Method on a Cuboid Lattice for Anisotropic and Inhomogeneous Flows
by Eman Yahia, William Schupbach and Kannan N. Premnath
Fluids 2021, 6(9), 326; https://doi.org/10.3390/fluids6090326 - 10 Sep 2021
Cited by 8 | Viewed by 1883
Abstract
Lattice Boltzmann (LB) methods are usually developed on cubic lattices that discretize the configuration space using uniform grids. For efficient computations of anisotropic and inhomogeneous flows, it would be beneficial to develop LB algorithms involving the collision-and-stream steps based on orthorhombic cuboid lattices. [...] Read more.
Lattice Boltzmann (LB) methods are usually developed on cubic lattices that discretize the configuration space using uniform grids. For efficient computations of anisotropic and inhomogeneous flows, it would be beneficial to develop LB algorithms involving the collision-and-stream steps based on orthorhombic cuboid lattices. We present a new 3D central moment LB scheme based on a cuboid D3Q27 lattice. This scheme involves two free parameters representing the ratios of the characteristic particle speeds along the two directions with respect to those in the remaining direction, and these parameters are referred to as the grid aspect ratios. Unlike the existing LB schemes for cuboid lattices, which are based on orthogonalized raw moments, we construct the collision step based on the relaxation of central moments and avoid the orthogonalization of moment basis, which leads to a more robust formulation. Moreover, prior cuboid LB algorithms prescribe the mappings between the distribution functions and raw moments before and after collision by using a moment basis designed to separate the trace of the second order moments (related to bulk viscosity) from its other components (related to shear viscosity), which lead to cumbersome relations for the transformations. By contrast, in our approach, the bulk and shear viscosity effects associated with the viscous stress tensor are naturally segregated only within the collision step and not for such mappings, while the grid aspect ratios are introduced via simpler pre- and post-collision diagonal scaling matrices in the above mappings. These lead to a compact approach, which can be interpreted based on special matrices. It also results in a modular 3D LB scheme on the cuboid lattice, which allows the existing cubic lattice implementations to be readily extended to those based on the more general cuboid lattices. To maintain the isotropy of the viscous stress tensor of the 3D Navier–Stokes equations using the cuboid lattice, corrections for eliminating the truncation errors resulting from the grid anisotropy as well as those from the aliasing effects are derived using a Chapman–Enskog analysis. Such local corrections, which involve the diagonal components of the velocity gradient tensor and are parameterized by two grid aspect ratios, augment the second order moment equilibria in the collision step. We present a numerical study validating the accuracy of our approach for various benchmark problems at different grid aspect ratios. In addition, we show that our 3D cuboid central moment LB method is numerically more robust than its corresponding raw moment formulation. Finally, we demonstrate the effectiveness of the 3D cuboid central moment LB scheme for the simulations of anisotropic and inhomogeneous flows and show significant savings in memory storage and computational cost when used in lieu of that based on the cubic lattice. Full article
(This article belongs to the Special Issue Complex Fluids and Flows: Algorithms and Applications)
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26 pages, 12761 KiB  
Article
2D Hydrodynamics of a Plate: From Creeping Flow to Transient Vortex Regimes
by Yuli D. Chashechkin and Iaroslav V. Zagumennyi
Fluids 2021, 6(9), 310; https://doi.org/10.3390/fluids6090310 - 31 Aug 2021
Cited by 4 | Viewed by 1961
Abstract
Based on the numerical and experimental visualization methods, the flow patterns around a uniformly moving plate located at an arbitrary angle of attack are studied. The study is based on the fundamental equations of continuity, momentum and stratifying substance transport for the cases [...] Read more.
Based on the numerical and experimental visualization methods, the flow patterns around a uniformly moving plate located at an arbitrary angle of attack are studied. The study is based on the fundamental equations of continuity, momentum and stratifying substance transport for the cases of strong and weak stratified fluids, as well as potential and actually homogeneous ones. The visualization technique and computation codes were compiled bearing in mind conditions of internal waves, vortices, upstream, and downstream wakes registration, as well as the resolution of ligaments in the form of thin interfaces in schlieren flow images. The analysis was carried out in a unified mathematical formulation for a wide range of plate motion parameters, including slow diffusion-induced flows and fast transient vortex flows. The patterns of formation and subsequent evolution of the basic structural components, such as upstream disturbances, downstream wake, internal waves, vortices, and ligaments, are described both at start of motion and subsequent uniform movement of the plate. Calculations of forces acting on the obstacle in the flow were carried out to study effects of variations in fluid properties, flow conditions and plate parameters on the dynamic characteristics of the obstacle. The numerical and experimental results on the flow patterns around a plate are in a good agreement with each other for different flow regimes. Full article
(This article belongs to the Special Issue Complex Fluids and Flows: Algorithms and Applications)
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25 pages, 9478 KiB  
Article
An Improved Conservative Direct Re-Initialization Method (ICDR) for Two-Phase Flow Simulations
by Mehdi Mostafaiyan, Sven Wießner, Gert Heinrich and Mahdi Salami Hosseini
Fluids 2021, 6(7), 261; https://doi.org/10.3390/fluids6070261 - 20 Jul 2021
Cited by 2 | Viewed by 1452
Abstract
We introduce an improved conservative direct re-initialization (ICDR) method (for two-phase flow problems) as a new and efficient geometrical re-distancing scheme. The ICDR technique takes advantage of two mass-conserving and fast re-distancing schemes, as well as a global mass correction concept to reduce [...] Read more.
We introduce an improved conservative direct re-initialization (ICDR) method (for two-phase flow problems) as a new and efficient geometrical re-distancing scheme. The ICDR technique takes advantage of two mass-conserving and fast re-distancing schemes, as well as a global mass correction concept to reduce the extent of the mass loss/gain in two- and three-dimensional (2D and 3D) problems. We examine the ICDR method, at the first step, with two 2D benchmarks: the notched cylinder and the swirling flow vortex problems. To do so, we (for the first time) extensively analyze the dependency of the regenerated interface quality on both time-step and element sizes. Then, we quantitatively assess the results by employing a defined norm value, which evaluates the deviation from the exact solution. We also present a visual assessment by graphical demonstration of original and regenerated interfaces. In the next step, we investigate the performance of the ICDR in three-dimensional (3D) problems. For this purpose, we simulate drop deformation in a simple shear flow field. We describe our reason for this choice and show that, by employing the ICDR scheme, the results of our analysis comply with the existing numerical and experimental data in the literature. Full article
(This article belongs to the Special Issue Complex Fluids and Flows: Algorithms and Applications)
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19 pages, 8086 KiB  
Article
Effectiveness of Magnetized Flow on Nanofluid Containing Gyrotactic Micro-Organisms over an Inclined Stretching Sheet with Viscous Dissipation and Constant Heat Flux
by Hossam A. Nabwey, S.M.M. El-Kabeir, A.M. Rashad and M.M.M. Abdou
Fluids 2021, 6(7), 253; https://doi.org/10.3390/fluids6070253 - 12 Jul 2021
Cited by 5 | Viewed by 1789
Abstract
The bioconvection phenomenon, through the utilization of nanomaterials, has recently encountered significant technical and manufacturing applications. Bioconvection has various applications in bio-micro-systems due to the improvement it brings in mixing and mass transformation, which are crucial problems in several micro-systems. The present investigation [...] Read more.
The bioconvection phenomenon, through the utilization of nanomaterials, has recently encountered significant technical and manufacturing applications. Bioconvection has various applications in bio-micro-systems due to the improvement it brings in mixing and mass transformation, which are crucial problems in several micro-systems. The present investigation aims to explore the bioconvection phenomenon in magneto-nanofluid flow via free convection along an inclined stretching sheet with useful characteristics of viscous dissipation, constant heat flux, solutal, and motile micro-organisms boundary conditions. The flow analysis is addressed based on the Buongiorno model with the integration of Brownian motion and thermophoresis diffusion effects. The governing flow equations are changed into ordinary differential equations by means of appropriate transformation; they were solved numerically using the Runge–Kutta–Fehlberg integration scheme shooting technique. The influence of all the sundry parameters is discussed for local skin friction coefficient, local Nusselt number, local Sherwood number, and local density of the motile micro-organisms number. Full article
(This article belongs to the Special Issue Complex Fluids and Flows: Algorithms and Applications)
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22 pages, 32778 KiB  
Article
CFD Model for Aircraft Ground Deicing: Verification and Validation of an Extended Enthalpy-Porosity Technique in Particulate Two Phase Flows
by Sami Ernez and François Morency
Fluids 2021, 6(6), 210; https://doi.org/10.3390/fluids6060210 - 7 Jun 2021
Cited by 1 | Viewed by 2473
Abstract
Researchers have focused in the last five years on modelling the aircraft ground deicing process using CFD (computational fluid dynamics) in order to reduce its costs and pollution. As preliminary efforts, those studies did not model the ice melting nor the diffusion between [...] Read more.
Researchers have focused in the last five years on modelling the aircraft ground deicing process using CFD (computational fluid dynamics) in order to reduce its costs and pollution. As preliminary efforts, those studies did not model the ice melting nor the diffusion between deicing fluids and water resulting from the melting process. This paper proposes a CFD method to simulate this process filling these gaps. A particulate two-phase flow approach is used to model the spray impact on ice near the contaminated surface. Ice melting is modelled using an extended version of the enthalpy-porosity technique. The water resulting from the melting process is diffused into the deicing fluid forming a single-phase film. This paper presents a new model of the process. The model is verified and validated through three steps. (i) verification of the species transport. (ii) validation of the transient temperature field of a mixture. (iii) validation of the convective heat transfer of an impinging spray. The permeability coefficient of the enthalpy-porosity technique is then calibrated. The proposed model proved to be a suitable candidate for a parametric study of the aircraft ground deicing process. On the validation test cases, the precision of heat transfer prediction exceeds 88%. The model has the ability of predicting the deicing time and the deicing fluid quantities needed to decontaminate a surface. Full article
(This article belongs to the Special Issue Complex Fluids and Flows: Algorithms and Applications)
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23 pages, 2710 KiB  
Article
Low-Noise Synthetic Turbulence Tailored to Lateral Periodic Boundary Conditions
by Tommy Rigall, Benjamin Cotté and Philippe Lafon
Fluids 2021, 6(6), 193; https://doi.org/10.3390/fluids6060193 - 21 May 2021
Cited by 2 | Viewed by 1691
Abstract
The present work is dedicated to turbulence synthesis tailored to lateral periodic boundary conditions for direct noise computations through compressible large eddy simulations. Synthetic turbulence can be essential for aeroacoustic applications when computing airfoil turbulent inflow noise or for accurately capturing the behavior [...] Read more.
The present work is dedicated to turbulence synthesis tailored to lateral periodic boundary conditions for direct noise computations through compressible large eddy simulations. Synthetic turbulence can be essential for aeroacoustic applications when computing airfoil turbulent inflow noise or for accurately capturing the behavior of boundary layers. This behavior determines both trailing edge noise and complex flow structures such as laminar separation bubbles. For airfoil simulation purposes, spanwise periodic boundary conditions are usually considered. If synthetic perturbations are injected without observing the periodicity rule, strong spurious pressure waves are emitted and pollute the entire computational domain. In this work, the random Fourier modes method for turbulence generation is adapted in order to respect the spanwise periodicity constraint right at the computational domain inlet. This approach does not affect the turbulence properties such as the spectral shape and the turbulent kinetic energy decay. Since the emphasis is put on the generation and convection of the turbulence, only the turbulence convection region between the inlet and the airfoil is considered in this paper, without the airfoil. Two geometrical configurations are tested: the first one is a simple box with a constant mesh size, and the second one concentrates the fine cells on the area in front of the airfoil. In the second configuration, the computational cost is reduced by up to 25%, but more spurious noise is present because of interpolation areas between different grids using the Chimera method. Finally, the results’ reproducibility is assessed using different turbulence realizations. Full article
(This article belongs to the Special Issue Complex Fluids and Flows: Algorithms and Applications)
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14 pages, 1108 KiB  
Article
Precise Method to Estimate the Herschel-Bulkley Parameters from Pipe Rheometer Measurements
by Elie Magnon and Eric Cayeux
Fluids 2021, 6(4), 157; https://doi.org/10.3390/fluids6040157 - 14 Apr 2021
Cited by 18 | Viewed by 6461
Abstract
Accurate characterization of the rheological behavior of non-Newtonian fluids is critical in a wide range of industries as it governs process efficiency, safety, and end-product quality. When the rheological behavior of fluid may vary substantially over a relatively short period of time, it [...] Read more.
Accurate characterization of the rheological behavior of non-Newtonian fluids is critical in a wide range of industries as it governs process efficiency, safety, and end-product quality. When the rheological behavior of fluid may vary substantially over a relatively short period of time, it is desirable to measure its viscous properties on a more continuous basis than relying on spot measurements made with a viscometer on a few samples. An attractive solution for inline rheological measurements is to measure pressure gradients while circulating fluid at different bulk velocities in a circular pipe. Yet, extracting the rheological model parameters may be challenging as measurement uncertainty may influence the precision of the model fitting. In this paper, we present a method to calibrate the Herschel-Bulkley rheological model to a series of differential pressure measurements made at variable bulk velocities using a combination of physics-based equations and nonlinear optimization. Experimental validation of the method is conducted on non-Newtonian shear-thinning fluid based on aqueous solutions of polymers and the results are compared to those obtained with a scientific rheometer. It is found that using a physics-based method to estimate the parameters contributes to reducing prediction errors, especially at low flow rates. With the tested polymeric fluid, the proportion difference between the estimated Herschel-Bulkley parameters and those obtained using the scientific rheometer are −24% for the yield stress, 0.26% for the consistency index, and 0.30% for the flow behavior index. Finally, the computation requires limited resources, and the algorithm can be implemented on low-power devices such as an embedded single-board computer or a mobile device. Full article
(This article belongs to the Special Issue Complex Fluids and Flows: Algorithms and Applications)
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