Fluid Flow In Complex Geometries Research Articles

Hybrid quantum physics-informed neural networks for simulating computational fluid dynamics in complex shapes

Finding the distribution of the velocities and pressures of a fluid by solving the Navier–Stokes equations is a principal task in the chemical, energy, and pharmaceutical industries, as well as in mechanical engineering and in design of pipeline systems. With existing solvers, such as OpenFOAM and Ansys, simulations of fluid dynamics in intricate geometries are computationally expensive and require re-simulation whenever the geometric parameters or the initial and boundary conditions are altered. Physics-informed neural networks (PINNs) are a promising tool for simulating fluid flows in complex geometries, as they can adapt to changes in the geometry and mesh definitions, allowing for generalization across fluid parameters and transfer learning across different shapes. We present a hybrid quantum PINN (HQPINN) that simulates laminar fluid flow in 3D Y-shaped mixers. Our approach combines the expressive power of a quantum model with the flexibility of a PINN, resulting in a 21% higher accuracy compared to a purely classical neural network. Our findings highlight the potential of machine learning approaches, and in particular HQPINN, for complex shape optimization tasks in computational fluid dynamics. By improving the accuracy of fluid simulations in complex geometries, our research using hybrid quantum models contributes to the development of more efficient and reliable fluid dynamics solvers.

Numerical analysis on hydrate production performance with multi-well systems: Synergistic effect of adjacent wells and implications on field exploitation

Multi-well technology is an alternative method to achieve commercialization development of the gas hydrate, which further requires proper production strategies. However, its stimulation mechanisms remain unclear, especially the synergistic effects of adjacent wells, restricting the production strategy formulation. Thus, we established a 3D model to characterize multi-physics fields, flow characteristics, as well as productivity of hydrate reservoirs on a large scale. It can display the fluid flow in complex geometries, realizing the accurate characterization of the flow field during hydrate production with multi-well systems. Total productivity of optimal multi-well systems can be 1.44 times higher than all single wells independently, Meanwhile, physical fields and flow characteristics alter with the well position as well as well number. After that, an index Ise is proposed to realize the quantitative evaluation of the impact of synergistic effect on productivity. The impact of synergistic effect strengthens continuously versus duration time and well spacing. In addition, the occurring synergistic effect can increase productivity by promoting hydrate dissociation in expanded pressure drop areas. In contrast, the fluid resistance effect decreases the per-well produced gas and water due to inflow reduction induced by inter-well interference. Moreover, an estimation model is established to identify the proper well spacing for lower drilling costs and larger productivity. This work will enable the extended application of multi-well systems with the synergistic effect and further promote the efficient development of the gas hydrate.

Analysis of droplet behavior and breakup mechanisms on wet solid surfaces

The behavior and dynamics of droplet spreading are pivotal phenomena that exert a profound influence on numerous scientific disciplines, technological advancements, and natural processes. This study was conducted with the aim to investigate factors influencing the shape and geometry of a liquid droplet on a solid surface using the lattice Boltzmann method (LBM). LBM as a mesoscale numerical fluid simulation has gained increasing popularity among the most favorable numerical methods for simulating multi-phase/multi-component fluid flow in complex geometries. Accordingly, parameters dependency, surface tension, two-phase diagram, and wettability were evaluated in the LBM, and stable and calibrated forms were used for the droplet simulations. Also, an equation was obtained to determine the contact angle in the LBM system with a determination coefficient of 0.988. Then, droplet behavior was examined for its dependency on wettability, interfacial tension, and line tension. The results showed droplets breakup in a certain interfacial tension at high adhesive force. These breakups were due to the force balance in the triple line. They were not monotonic and first decreased and then increased the volume of the droplets.

Numerical simulation of a turbulent Lead Bismuth Eutectic flow inside a 19 pin nuclear reactor bundle with a four logarithmic parameter turbulence model

Computational Fluid Dynamic allows scientists and engineers to investigate fluid flow in complex geometries and evaluate heat transfer between a solid body and a fluid. In the present paper we study the heat transfer of a Lead Bismuth Eutectic (LBE) turbulent flow in a bare 19 pin nuclear reactor bundle. When dealing with low Prandtl number fluids, like LBE for which Pr = 0.025, proper turbulence models are needed to improve the prediction of heat transfer. We use here a four logarithmic parameter turbulence model in order to calculate Reynolds stresses and turbulent heat flux. In particular, an equation for temperature fluctuations and one for their dissipation are solved. These variables are used to model thermal characteristic time scales. The results are reported for different values of the Peclet number and a fixed value of the pitch to diameter ratio. The obtained values of the Nusselt number are compared with experimental correlations, that can be found in literature, and with the ones obtained using a Simple Eddy Diffusivity model, where the eddy thermal diffusivity is calculated as proportional to eddy viscosity through a modeled turbulent Prandtl number.

Lattice Boltzmann model for three-phase viscoelastic fluid flow.

A lattice Boltzmann (LB) framework is developed for simulation of three-phase viscoelastic fluid flows in complex geometries. This model is based on a Rothman-Keller type model for immiscible multiphase flows which ensures mass conservation of each component in porous media even for a high density ratio. To account for the viscoelastic effects, the Maxwell constitutive relation is correctly introduced into the momentum equation, which leads to a modified lattice Boltzmann evolution equation for Maxwell fluids by removing the normal but excess viscous term. Our simulation tests indicate that this excess viscous term may induce significant errors. After three benchmark cases, the displacement processes of oil by dispersed polymer are studied as a typical example of three-phase viscoelastic fluid flow. The results show that increasing either the polymer intrinsic viscosity or the elastic modulus will enhance the oil recovery.

Patient-Specific Modeling of Hemodynamics: Supporting Surgical Planning in a Fontan Circulation Correction

Computational fluid dynamics (CFD) is a modeling technique that enables calculation of the behavior of fluid flows in complex geometries. In cardiovascular medicine, CFD methods are being used to calculate patient-specific hemodynamics for a variety of applications, such as disease research, noninvasive diagnostics, medical device evaluation, and surgical planning. This paper provides a concise overview of the methods to perform patient-specific computational analyses using clinical data, followed by a case study where CFD-supported surgical planning is presented in a patient with Fontan circulation complicated by unilateral pulmonary arteriovenous malformations. In closing, the challenges for implementation and adoption of CFD modeling in clinical practice are discussed.

A coupled element-based finite-volume method for the solution of incompressible Navier-Stokes equations

ABSTRACTThis article presents a new element-based finite-volume discretization approach for the solution of incompressible flow problems on co-located grids. The proposed method, called the method of proper closure equations (MPCE), employs a proper set of physically relevant equations to constrain the velocity and pressure at integration points. These equations provide a proper coupling between the nodal values of pressure and velocity. The final algebraic equations are not segregated in this study and are solved in a fully coupled manner. To show the applicability and performance of the method, it is tested on several steady two-dimensional laminar-flow benchmark cases. The results indicate that the method simulates the fluid flow in complex geometries and on nonorthogonal computational grids accurately. Also, it is shown that the method is robust in the sense that it does not require severe underrelaxation even at relatively high Reynolds numbers. In each test case, the required underrelaxation parameter, the number of iterations, and the corresponding CPU time are reported.

ASSESSMENT OF A LATTICE BOLTZMANN MODEL TO SIMULATE FLUID FLOWS WITH COMPLEX GEOMETRIES

Lately, the lattice Boltzmann method (LBM) has proven to be a promising approach to solve complex fluid flows and transport phenomena. In the present contribution, the LB-BGK model, also called single relaxation time (SRT), is used to handle fluid flows in complex geometries. The model is first benchmarked via the 2D Poiseuille flow problem to conduct a discussion on its accuracy and performance. The accuracy of the LBM is weighted by several factors; among these we investigated the effect of the boundary conditions, the spatial resolution, the Mach number, and the choice of relaxation factors. It is found that the considered LBM is highly dependent on the physical problem, the numerical implementation, and the used parameters. However, a set of correlated optimal parameters is suggested to improve the accuracy and decrease both discretization and compressibility errors. In addition, we discussed the ability of the current model to handle complex geometries. The simulation of fluid past a circular or square cylinder in a confined geometry has been successfully achieved, even when curves are modeled as stairs. In light of the obtained results, we can state that the proposed model has high potential to handle problems with complex flows and geometries.

The projection method for fluid flows in complex geometries

Abstract In this paper, we develop a numerical method for solving two dimensional viscous flow problems in the presence of obstacles in unsteady regime. In fact, the present study is based on a Chorin type Projection method [1] of first order in time and second order of accuracy in space, on a staggered grid [9]. Here we consider flows with incompressibility and solid constraints for an horizontal fluid flow [3]. Results of this study are presented for the Navier-Stokes equations in order to show the efficiency of the method for complex fluid flows.

Modelling of solidification process of aluminium foams using lattice Boltzmann method

This study is devoted to developing a numerical model of aluminium melt added as a gassing agent and then heated to a certain temperature to obtain metallic foam. First, a powerful data processing method, i.e. the lattice Boltzmann method on network, is studied. This model considers the variety of complex boundary conditions, the simple and multiphase fluid flow in complex geometries, the stabilisation of the foams, the influence of the parameters depending on the local fluctuations of the metal foam pressure and the mutual interactions between the bubbles inside this foam. Second, the Navier–Stokes equation is applied to elucidate the fluid flows in the liquid. In addition, the diffusion equation for the hydrogen transport, the distribution of temperature, the density and the kinetic equations are studied as well. The Boltzmann algorithm on network is applied to solve the incompressible Navier–Stokes equations. Finally, a three-dimensional simulation method and calculation algorithm to discretise the complex physical processes is carried out. Moreover, the foaming experiment was performed to learn the main technological parameters.

A flexible high‐performance Lattice Boltzmann GPU code for the simulations of fluid flows in complex geometries

AbstractWe describe the porting of the Lattice Boltzmann component of MUPHY, a multi‐physics/scale simulation software, to multiple graphics processing units using the Compute Unified Device Architecture. The novelty of this work is the development ofad hoctechniques for optimizing the indirect addressing that MUPHY uses for efficient simulations of irregular domains. Copyright © 2009 John Wiley & Sons, Ltd.

Immersed boundary computations of shear- and buoyancy-driven flows in complex enclosures

Cartesian grids used with the immersed boundary method (IBM) offer an attractive alternative for simulating fluid flows in complex geometries. We present a ghost fluid method for incompressible flows solved with staggered grids. The primary feature is the satisfaction of local mass continuity for ghost pressure cells, rather than extrapolating the pressures from within the flow domain. The method preserves local continuity in each cell and also global continuity. As a result, no explicit mass sources or sinks are needed. We have applied the method to study shear- and buoyancy-driven flows in a number of complex cavities.

A robust algorithm for computing fluid flows on highly non‐smooth staggered grids

AbstractA new method for computing the fluid flow in complex geometries using highly non‐smooth and non‐orthogonal staggered grid is presented. In a context of the SIMPLE algorithm, pressure and physical tangential velocity components are used as dependent variables in momentum equations. To reduce the sensitivity of the curvature terms in response to coordinate line orientation change, these terms are exclusively computed using Cartesian velocity components in momentum equations. The method is then used to solve some fairly complicated 2‐D and 3‐D flow field using highly non‐smooth grids. The accuracy of results on rough grids (with sharp grid line orientation change and non‐uniformity) was found to be high and the agreement with previous experimental and numerical results was quite good. Copyright © 2008 John Wiley & Sons, Ltd.

HemeLB: A high performance parallel lattice-Boltzmann code for large scale fluid flow in complex geometries

We describe a parallel lattice-Boltzmann code for efficient simulation of fluid flow in complex geometries. The lattice-Boltzmann model and the structure of the code are discussed. The fluid solver is highly optimized and the resulting computational core is very fast. Furthermore, communication is minimized and the novel topology-aware domain decomposition technique is shown to be very effective for large systems, allowing us to tune code execution in geographically distributed cross-site simulations. The benchmarks presented indicate that very high performance can be achieved.

An Efficient and Robust Numerical Scheme for the SIMPLER Algorithm on Non-Orthogonal Curvilinear Coordinates: CLEARER

In this article, an Improved SIMPLER (CLEARER) algorithm is formulated to solve the incompressible fluid flow and heat transfer on the nonstaggered, nonorthogonal curvilinear grid system. By virtue of a modified momentum interpolation method in calculating the interface contravariant velocity in both the predictor step and the corrector step, the coupling between pressure and velocity is fully guaranteed, and the conservation law is also satisfied. A second relaxation factor is introduced in the corrector step, of which the convergent solution is independent. By setting the second relaxation factor less than the underrelaxation factor for the velocity to some extent, both the convergence rate and robustness can be greatly enhanced. Meanwhile, the CLEARER algorithm can also overcome the severe grid nonorthogonality. With the simplified pressure-correction equation, the convergent solution can still be obtained even when the intersection angle among grid lines is as low as 1°, which may provide valuable guidance in studying the fluid flow in complex geometries.

Mesh Construction from Medical Imaging for Multiphysics Simulation: Heat Transfer and Fluid Flow in Complex Geometries

Medical imaging techniques, such as MRI and CT scanning, are valuable tools for reconstructing the geometry of complex objects. Much effort has been applied in the biomechanical research field to develop image processing software capable of generating valid meshes for computational continuum mechanics packages from such scans. To date these techniques have largely been applied to computation of single physical processes, e.g., fluid flow or stress analysis. We describe techniques for image to mesh conversion which permit the creation of multiple meshes for distinct volumes of the object, ensuring absolute conformity between the meshes on shared boundaries and allowing computation of coupled physical processes on distinct subregions of the total volume. Such techniques have application well beyond the biomedical field, and we illustrate the possibilities with coupled fluid flow/heat transfer calculations for an apple pie and a metal foam.

Simplified CFD approach of a hollow fiber ultrafiltration system

Abstract Pressure driven membrane filtration processes have emerged as cost effective and confirmed technologies. Ultrafiltration is used to produce drinking water. Hollow fiber membranes are used in industrial processes but there is still a need of predicting pressure drops for design and optimization purposes: to control the production of water, to anticipate problems such as the clogging of the hollow fibers and/or the module position and to consider energy consumption. This prediction could also enhance current models that calculate pressure drop using the Hagen–Poiseuille law. In this work, the flow characteristics controlling the performance of a hollow fiber membrane module are investigated numerically. The aim of this study is to determine the pressure drop in a module depending on the operating conditions and membrane characteristics: a simplified model equation is proposed. We use a commercial CFD package (FLUENT). Numerical simulation can provide a better understanding of module performance, especially for permeable wall and/or complex multi-component systems. CFD can be used to better apprehend fluid flows in complex geometries and to test the influence of process parameters. The results are compared to experimental data obtained with an industrial pilot plant: a good agreement with our relation is obtained.

Multiscale modeling of fluid transport in heterogeneous materials using discrete Boltzmann methods

The lattice Boltzmann method is a promising approach for modeling single and multicomponent fluid flow in complex geometries like porous materials. Here, we review some of our previous work and discuss some recent developments concerning fluid flow in multiple pore size materials. After presenting some simple test cases to validate the model, results from large scale simulations of single and multi-component fluid flow through digitized Fontainebleau sandstone, generated by X-Ray microtomography, are given. Reasonably good agreement was found when compared to experimentally determined values of permeability for similar rocks. Finally, modification of the lattice Boltzmann equations, to describe flow in microporous materials, is described. The potential for modeling flows in other microstructures of interest to concrete technology will be discussed.

A Characteristic Galerkin Method for Discrete Boltzmann Equation

The characteristic Galerkin finite element method for the discrete Boltzmann equation is presented to simulate fluid flows in complex geometries. The inherent geometric flexibility of the finite element method permits the easy use of simple Cartesian variables on unstructured meshes and the mesh clustering near large gradients. The characteristic Galerkin procedure with appropriate boundary condition results in accurate solutions with little numerical diffusion. Several test cases are conducted, including unsteady Couette flows, lid-driven cavity flows, and steady flow past a circular cylinder on unstructured meshes. The numerical results are in good agreement with previous analytical (if applicable), numerical, and experimental results.

The generation of an orthogonal grid by the use of a boundary integral technique

A new boundary integral technique is developed for the two-dimensional, irrotational, incompressible fluid flow in complex geometries and the method is applied to the generation of an orthogonal grid system which can be used for solving laminar and turbulent fluid flows in the same geometries. The integral equation for the potential flow is derived from the Dirichlet boundary problem for an analytical function on the upper half plane, and then the integral-differential equations are obtained on the boundary of the solution domain in the physical plane. An iterative procedure is developed to solve the integral-differential equations in order to obtain the potential flow solution. To illustrate the grid generation technique several classical two-dimensional CFD problems have been investigated and the method has been extended to generate a less distorted grid system for a three-dimensional fluid flow.