Multiphase Fluid Simulation Research Articles

Real-time screen space rendering method for particle-based multiphase fluid simulation

Existing fluid simulation techniques mainly process single-phase fluids, and they have difficulties in accurately simulating and visualizing multiphase fluid dynamics. This paper proposes a new method for the real-time rendering of multiphase fluid simulations, which uses smoothed particle hydrodynamics in screen space. Meanwhile, the method employs phase fraction textures to differentiate various materials in multiphase fluid simulations, thereby portraying mixing and separation effects more realistically. Besides, efficient texture computation allows it to be integrated seamlessly into real-time simulation rendering workflows. Extensive testing confirms the effectiveness of the proposed method in rendering multiphase fluid behaviors with high visual fidelity and demonstrates its capability to process frames within 0.01 s, even in cases with up to 300,000 particles. This study enhances the fluid dynamics simulation field and provides a more accurate and efficient method for visualizing complex multiphase fluids in simulations.

A unified interaction model for multiphase flows with the lattice Boltzmann method

AbstractThe lattice Boltzmann method (LBM) has been increasingly adopted for modelling multiphase fluid simulations in engineering problems. Although relatively easy to implement, the ubiquitous Shan–Chen pseudopotential model suffers from limitations such as thermodynamic consistency and the formation of spurious currents. In the literature, the Zhang–Chen, Kupershtokh et al., the β‐scheme, and the Yang–He alternative models seek to mitigate these effects. Here, through analytical manipulations, we call attention to a unified model from which these multiphase interaction forces can be recovered. Isothermal phase‐transition simulations of single‐component in stationary and oscillating droplet conditions, as well as spinodal decomposition calculations, validate the model numerically and reinforce that the multiphase forces are essentially equivalent. Parameters are selected based on the vapour densities at low temperatures in the Maxwell coexistence curve, where there is a narrow range of optimal values. We find that expressing the model parameters as functions of the reduced temperature further enhances the thermodynamic consistency without losing stability or increasing spurious velocities.

Efficient and practical phase-field method for the incompressible multi-component fluids on 3D surfaces with arbitrary shapes

The fluid dynamics on a curved surface can be used to approximately describe many physical phenomena in the natural world, such as the atmospherical circulation on a planet. The present work develops a simple, practical, and efficient numerical method for the multi-phase fluid simulations on arbitrarily curved surfaces in 3D space. The multi-component Cahn–Hilliard type phase-field fluid model is adopted to capture the motion of multiple interfaces. The velocity field and pressure are updated by solving the incompressible Navier–Stokes equations. To achieve the decoupled computations of pressure and velocity, the Chorin's projection method with pressure correction is considered. A linear semi-implicit time-marching scheme is designed for the phase-field equations. By adopting the embedding method and appropriate pseudo-Neumann boundary conditions, the direct calculations on the surface can be extended into a 3D narrow band domain including the surface. The standard Laplacian operator can be used to replace the surface Laplace–Beltrami operators and the finite difference method is used to perform the discretization in space. In each time step, all variables can be updated in a step-by-step manner because the proposed method is totally decoupled. Therefore, the whole algorithm is highly efficient and easy to implement. Extensive numerical experiments indicate that the proposed method has good performance for the multi-component simulations on curved surfaces with complex shapes.

Using Physics-Informed Generative Adversarial Networks to Perform Super-Resolution for Multiphase Fluid Simulations

AbstractComputational fluid dynamics (CFD) simulations are useful in the field of engineering design as they provide deep insights on product or system performance without the need to construct and test physical prototypes. However, they can be very computationally intensive to run. Machine learning methods have been shown to reconstruct high-resolution single-phase turbulent fluid flow simulations from low-resolution inputs. This offers a potential avenue towards alleviating computational cost in iterative engineering design applications. However, little work thus far has explored the application of machine learning image super-resolution methods to multiphase fluid flow (which is important for emerging fields such as marine hydrokinetic energy conversion). In this work, we apply a modified version of the super-resolution generative adversarial network (SRGAN) model to a multiphase turbulent fluid flow problem, specifically to reconstruct fluid phase fraction at a higher resolution. Two models were created in this work, one which incorporates a physics-informed term in the loss function and one which does not, and the results are discussed and compared. We found that both models significantly outperform non-machine learning upsampling methods and can preserve a substantial amount of detail, showing the versatility of the SRGAN model for upsampling multiphase fluid simulations. However, the difference in accuracy between the two models is minimal indicating that, in the context studied here, the additional complexity of a physics-informed approach may not be justified.

High Rate Deposition in Cold Spray

Industrialization of cold spray introduces concerns regarding the cost and time efficiency of cold spray procedures. In this work, high rate deposition of tantalum was studied computationally and experimentally. Quasi-1D multiphase fluid simulations predicted minimal effects on the bonding conditions of particles with 5% to 14% increase in powder-to-gas mass flow ratio. Experimental specimens were produced to observe the mechanical and microstructural effects of increased powder stream loading. Adhesion and hardness tests as well as thermal conductivity, optical microscopy, and electron backscatter diffraction examinations only exhibited minor differences in the mechanical and microstructural properties of the specimens. The increased powder stream loading rate, however, allows a significant reduction in the time required for depositing the same amount of tantalum by a factor of three. The results of the study enable shorter cold spray deposition time. This leads to significant cost savings associated with consumption of helium and labor, while facilitating shorter turn-around times for repairing components and manufacturing of cold-sprayed products.

A Divergence‐free Mixture Model for Multiphase Fluids

AbstractWe present a novel divergence free mixture model for multiphase flows and the related fluid‐solid coupling. The new mixture model is built upon a volume‐weighted mixture velocity so that the divergence free condition is satisfied for miscible and immiscible multiphase fluids. The proposed mixture velocity can be solved efficiently by adapted single phase incompressible solvers, allowing for larger time steps and smaller volume deviations. Besides, the drift velocity formulation is corrected to ensure mass conservation during the simulation. The new approach increases the accuracy of multiphase fluid simulation by several orders. The capability of the new divergence‐free mixture model is demonstrated by simulating different multiphase flow phenomena including mixing and unmixing of multiple fluids, fluid‐solid coupling involving deformable solids and granular materials.

A Unified Multiple-Phase Fluids Framework Using Asymmetric Surface Extraction and the Modified Density Model

Multiple-phase fluids’ simulation and 3D visualization comprise an important cooperative visualization subject between fluid dynamics and computer animation. Interactions between different fluids have been widely studied in both physics and computer graphics. To further the study in both areas, cooperative research has been carried out; hence, a more authentic fluid simulation method is required. The key to a better multiphase fluid simulation result is surface extraction. Previous works usually have problems in extracting surfaces with unnatural fluctuations or detail missing. Gaps between different phases also hinder the reality of simulation. In this paper, we propose a unified surface extraction approach integrated with a modified density model for the particle-based multiphase fluid simulation. We refine the original asymmetric smoothing kernel used in the color field and address a binary tree scheme for surface extraction. Besides, we employ a multiphase fluid framework with modified density to eliminate density deviation between different fluids. With the methods mentioned above, our approach can effectively reconstruct the fluid surface for particle-based multiphase fluid simulation. It can also resolve the issue of overlaps and gaps between different fluids, which has widely existed in former methods for a long time. The experiments carried out in this paper show that our approach is able to have an ideal fluid surface condition and have good interaction effects.

Multi-phase Fluid Simulation Based on Narrow-Band FLIP Method

Euler method and Lagrangian method is applicable for fluid of different deformation respectively. The fluid implicit particle (FLIP) method is a combination of Euler method and Lagrangian method which embodies the advantages of both in fluid simulation. While narrow-band FLIP (NBFLIP) method is an improved FLIP method which limits the particles within the Narrow Band near the interface. NBFLIP method improves the computational efficiency by eliminating particle outside the Narrow Band without degrading the details. In this paper, the multi-phase volume of fraction (VOF) model based on NBFLIP (NBFLIP-VOF) method is proposed. This is the first combination of multi-phase VOF model with NBFLIP method. The method employees a unified framework to deal with miscible and immiscible fluid simulation, the simulation results are highly consistent with the results from previous literature. The results show that the NBFLIP-VOF method has a good performance in the simulation of multi-phase flow, it also proves the reliability of the method and the adaptability in multi-phase fluid simulation.

Modeling multiphase flow: Spray breakup using volume of fluids in a dynamics LES FEM method

ABSTRACTCurrently, all commercial software for engine modeling investigates the dispersed droplet phase of the injection process. Understanding the effect of geometry of the injector nozzle, initial jet conditions, fluid properties in the liquid film, breakup, resulting droplet sizes, and distribution are of primary importance to improve fuel efficiency and lower gas emissions. We have developed an innovative computational method and models to make this atomization process more predictive: a multiscale, multiphase fluid simulation, using a volume-of-fluid method implemented in a large eddy simulation algorithm found in the new KIVA-hpFE, a finite element method flow solver for all flow regimes.

DYVERSO: A Versatile Multi‐Phase Position‐Based Fluids Solution for VFX

AbstractMany impressive fluid simulation methods have been presented in research papers before. These papers typically focus on demonstrating particular innovative features, but they do not meet in a comprehensive manner the production demands of actual VFX pipelines. VFX artists seek methods that are flexible, efficient, robust and scalable, and these goals often conflict with each other. In this paper, we present a multi‐phase particle‐based fluid simulation framework, based on the well‐known Position‐Based Fluids (PBF) method, designed to address VFX production demands. Our simulation framework handles multi‐phase interactions robustly thanks to a modified constraint formulation for density contrast PBF. And, it also supports the interaction of fluids sampled at different resolutions. We put special care on data structure design and implementation details. Our framework highlights cache‐efficient GPU‐friendly data structures, an improved spatial voxelization technique based on Z‐index sorting, tuned‐up simulation algorithms and two‐way‐coupled collision handling based on VDB fields. Altogether, our fluid simulation framework empowers artists with the efficiency, scalability and versatility needed for simulating very diverse scenes and effects.

A general, mass-preserving Navier–Stokes projection method

The conservation of mass is a common issue with multiphase fluid simulations. In this work a novel projection method is presented which conserves mass both locally and globally. The fluid pressure is augmented with a time-varying component which accounts for any global mass change. The resulting system of equations is solved using an efficient Schur-complement method. Using the proposed method four numerical examples are performed: the evolution of a static bubble, the rise of a bubble, the breakup of a thin fluid thread, and the extension of a droplet in shear flow. The method is capable of conserving the mass even in situations with morphological changes such as droplet breakup.

A simple approach for bubble modelling from multiphase fluid simulation

This article presents a novel and flexible bubble modelling technique for multi-fluid simulations using a volume fraction representation. By combining the volume fraction data obtained from a primary multi-fluid simulation with simple and efficient secondary bubble simulation, a range of real-world bubble phenomena are captured with a high degree of physical realism, including large bubble deformation, sub-cell bubble motion, bubble stacking over the liquid surface, bubble volume change, dissolving of bubbles, etc. Without any change in the primary multi-fluid simulator, our bubble modelling approach is applicable to any multi-fluid simulator based on the volume fraction representation.

A narrow-band gradient-augmented level set method for multiphase incompressible flow

A finite-difference based numerical method for the simulation of multiphase incompressible flows is presented. The proposed algorithm adapts the gradient-augmented level set method of Nave et al. [25] for use in multiphase fluid simulations by interpolating the fluid velocity and introducing a simple reinitialization procedure. The method is carried out only along a narrow band surrounding the interface, reducing computational effort while preserving the advantages of the gradient-augmented method. Numerical results show excellent agreement with an analytical solution and available experimental data. A new experimental benchmark is introduced, using data gathered in a wedge-driven wave tank. In addition to the optimally local advection scheme and sub-grid resolution afforded by the new method, numerical comparisons with the standard level set method reveal superior volume conservation.

Controlling shapes of air bubbles in a multi-phase fluid simulation

Controlling shapes is a challenging problem in a multi-phase fluid simulation. Bubble particles enable the details of air bubbles to be represented within a simulation based on an Euler grid. We control the target shapes of bubbles by the gradient vectors of the signed distance field and attraction forces associated with control particles. Our hybrid approach enables to simulate physically plausible movements of bubbles while preserving the details of a target shape. Furthermore, we control the paths of moving bubbles using user-defined curves and the shape of an air bubbles by drag force. An accurate model of the drag force near the fluid surface means that bubbles have realistic ellipsoidal shapes.

Simulation of multiple fluids with solid–liquid phase transition

ABSTRACTPhysically based multiphase fluid simulation has been a hot topic in computer graphics. Since there are complex changing interface topology and interactions among air, solid, and different fluids, few papers have devoted to simulate the multiple fluids phenomena with solid–liquid phase transition. In this paper, the thermal fluid model for phase transition combined with free surface tracking is used to describe the interaction between air and fluids. Then a new model based on hierarchical lattice is proposed to process the solid–liquid interaction and the phase transition in the solid–liquid interface. Further, with the use of hybrid interaction with multidistribution functions, different realistic multiple fluids phenomena are rendered with different lattice sizes. Copyright © 2012 John Wiley & Sons, Ltd.

Evaluation of humped slab track performance in desert railways

The movement of sand dunes in desert railways has various harmful effects on conventional ballasted tracks. Ballast layer solidification and line closure due to the retention of sands are major problems in such areas. In this study, a new superstructure called ‘humped slab track’ is introduced which can obviate the main problems for desert railway tracks to a significant extent. This system applies the main advantage of the ballastless track which is theballast layer's elimination for avoiding the filling of ballast voids via sand dunes. Moreover, the rail seats in this superstructure were elevated above the slab level by means of reinforced concrete protuberances called humps. Hence, the transmission of sand dunes occurred through the transverse channels between the humps and beneath the rails. To demonstrate the efficiency of the proposed system, several multi-phase fluid simulations (involving solid sand particles and air) were accomplished using the computational fluid dynamic method. The results obtained for the maximum sand flow conditions show that the ballasted track needs to be closed after a very short time whereas the humped slab track is capable of enduring considerable sand flow conditions without any need for line closure.

Multi-phase fluid simulations using regional level sets

We address the problem of Multi-Phase (or Many-Phase) Fluid simulations. We propose to use the regional level set (RLS) that can handle a large number of regions and materials, and hence, is appropriate for simulations of many immiscible materials. Towards this goal, we improve the interpolation of the RLS, and develop the regional level set graph (RLSG), which registers connected components and their contacts, and tracks their properties such as region volumes, film life times, and film material types, as regions evolve, merge, split, or are squeezed into films. Using RLSG's tracking feature, we generate particles from tiny regions or rupturing films.

Simulation of swirling bubbly water using bubble particles

The effect of surface tension is dynamically and realistically represented within a multiphase fluid simulation. Air bubbles are seeded with ‘bubble particles’ which move randomly. These molecule-like movements modify the surface of the air bubbles and generate turbulence in the water. The surface tension between air bubble and water, determined by the composition of the water, remains constant regardless of the size of the bubble, while external forces cause unstable fluid motion as the surface tension strives to remain constant, bubbles split and merge. The bubble particles can also compute for the numerical dissipation usually experienced in grid-based fluid simulations, by restoring the lost volume of individual bubbles. The realistic tearing of bubble surfaces is shown in a range of examples.

Two equations of state assembled for basic analysis of multiphase CO2 flow and in deep sedimentary basin conditions

The purpose of the study presented in this manuscript is to describe and make available two equation-of-state (EOS) algorithms assembled for multiphase flow and transport of carbon dioxide (CO2). The algorithms presented here calculate solubility, compressibility factor, density, viscosity, fugacity, and enthalpy of CO2 in gaseous and supercritical phases, and mixtures or solutions of CO2 in water, as functions of pressure and temperature. Several features distinguish the two algorithms, but the primary distinction concerns treatment of supercritical/gas-phase CO2: one EOS we assembled is based on Redlich and Kwong's original algorithm developed in 1949, and the other is based on an algorithm developed by Span and Wagner in 1996. Both were modified for application to sedimentary basin studies of multiphase CO2 flow processes, including carbon sequestration applications. We present a brief comparison of these two EOS algorithms. Source codes for both algorithms are provided, including “stand-alone” Matlab © scripts for the interactive calculation of fluid properties at specified P–T conditions and FORTRAN subroutines for inclusion in existing FORTRAN multiphase fluid simulation packages. These routines are intended for fundamental analyses of CO2 sequestration and the like; more advanced studies, such as brine processes and reactive transport, require more advanced EOS algorithms.

118 Multi-phase fluid simulations by multi integrated moment formulation based on CIP-CSL Type Schemes

118 Multi-phase fluid simulations by multi integrated moment formulation based on CIP-CSL Type Schemes