Particle-based Fluid Research Articles

Lightweight particle-based real-time fluid simulation for mobile environment

This paper presents a real-time lightweight fluid simulation based on a particle fluid technique developed for mobile environment . The Bullet physics engine and smoothed particle hydrodynamic (SPH) fluid algorithm will be used for our lightweight fluid simulation. First, we describe an advanced collision detection mechanism that will be used. By using this method, less computational resources are required. Secondly, we present a simplified SPH algorithm where nearby particles are grouped together to minimize the number of calculations. By decreasing the number of particles, an improved computational performance is expected. Finally, the ARM NEON based parallel computing technique was enabled to reduce execution time by lowering the number of arithmetic instructions. Several experiments are carried out where the experimental results indicate the first technique led to a 50% improvement in performance. The second technique provided a 17% overall improvement. The third technique delivered a performance improvement within the range of 26%–40%. Overall, the experimental results show that the proposed techniques provided an accumulative performance improvement of approximately 120% for all applied methodologies.

Swelling-diffusion-interfacial polymerized core-shell typed polystyrene/poly(3, 4-ethylenedioxythiophene) microspheres and their electro-responsive characteristics

We synthesized core-shell structured conducting polystyrene/poly(3,4-ethylenedioxythiophene) (PS/PEDOT) microspheres and examined their electro-responsive electrorheological (ER) properties under an applied electric field when dispersed in a silicone oil. Monodisperse PS particles 1.05 μm in diameter were initially fabricated via dispersion polymerization, and PS/PEDOT microspheres with average diameters of approximately 1.07 μm were prepared by a swelling-diffusion-interfacial polymerization process. The morphology of the PS/PEDOT microspheres was confirmed by both field emission scanning electron microscopy and transmission electron microscopy, while their chemical structure was characterized by Fourier transform infrared spectroscopy. Formation of particle chains in the ER fluid was directly observed by optical microscopy under an applied electric field. The rheological behavior of the PS/PEDOT particle-based ER fluid was examined using a rotational rheometer on particles dispersed in silicone oil at a volume fraction of 10%. As the electric field was strengthened, the performance of the ER fluid was also enhanced. The dielectric spectra were also well correlated to their ER effects using an LCR meter.

Physics-inspired approach to realistic and stable water spray with narrowband air particles

We propose an efficient and physics-inspired method for producing water spray effects by modeling air particles within a narrowband of the water surface in particle-based water simulation. In the real world, water and air continuously interact with each other around free surfaces, and this phenomenon is commonly observed in waterfalls or in rough sea waves. Due to the small volume of water spray, the interfaces between water and air become vague, and the interactions between water and air lead to strong vortex phenomena. To express these phenomena, we propose the generation of narrowband air cells in particle-based water simulations and the expression of water spray effects by creating and evolving air particles in narrowband air cells. We guarantee the robustness of the simulation by solving the drifting problem that occurs when the number of adjacent air particles is insufficient. Experiments convincingly demonstrate that the proposed approach is efficient and easy to use while delivering high-quality results. We produce efficient water spray effects from coarse simulation as an independent post-process that can be applied to most particle-based fluid solvers.

Reducing the effects of compressibility in DPD-based blood flow simulations through severe stenotic microchannels

Viscous fluid flow simulations based on dissipative particle dynamics (DPD) may bear compressible flow effects when flowing through severe stenotic geometries. This is caused by the soft repulsive potential employed in the DPD force field, which limits the particle-based fluid system ability to sustain a large degree of compression. To mitigate this problem, a Morse potential was added to the DPD force field. We studied the fluid properties of the modified fluid model (DPD–Morse) and compared it with a previously published conventional DPD based fluid model. Our DPD–Morse model demonstrated reduced compressibility while preserving other fluid properties such as the fluid density and viscosity. We further investigated the fluid flow properties for a severe 3D stenotic microchannel with a 67% stenosis, using the two models. The DPD fluid model presented a significant density gradient along the flow direction, where the fluid density increased upstream towards the stenosis and decreased downstream from the stenosis before regaining its initial value. In contrast, the DPD–Morse model demonstrated a far better uniform fluid density distribution along the flow direction. We compared both solutions with CFD simulations. The DPD–Morse fluid resembled the behavior of the continuum fluid model whereas DPD fluid deviated from it. To estimate the effect that the difference between the two DPD formulations may have on the platelet activation potential, we have further embedded a platelet model within the flow field and investigated the shear stress accumulation along the platelet transport trajectory. In the stenotic section, the DPD fluid demonstrated a larger stress gradient than the DPD–Morse fluid. The platelet transport period was shorter for the DPD fluid as it generated a larger fluid density gradient that overestimated the acceleration of the platelet through the stenosis. With reduced fluid compressibility, our modified DPD–Morse fluid model was more accurate than the DPD fluid model when computing the platelet activation potential in a severe stenosis.

Coherent spherical range-search for dynamic points on GPUs

We present an approach to accelerate spherical range-search (SRS) for dynamic points that employs the computational power of many-core GPUs. Unlike finding kapproximate nearest neighbours (ANNs), exact SRS is needed in geometry processing and physical simulation to avoid missing small features. The spatial coherence of query points and the temporal coherence of dynamic points are exploited in our approach to achieve very efficient range-search on AABB-trees. We test our coherent SRS in several applications including point-point-set geometry processing, distance-field generation and particle-based simulation, which are best scenarios to present the spatial and the temporal coherence of spherical queries on dynamic points. On a PC with NVIDIA GTX 660 Ti GPUs, our approach can take 1M queries on 1M dynamic points at a rate of 1600 queries/ms, where 49 neighbours are found on average within the range of 1/100 of the bounding-box’s diagonal length. We observe an increase of up to 4x compared with conventional voxel-based GPU searching approaches in the benchmark of particle-based fluid simulation. Moreover, the speedup can be scaled up to 150x when being applied to highly non-uniform distribution of particles in the simulation.

Rigid Body Sampling and Individual Time Stepping for Rigid-Fluid Coupling of Fluid Simulation

In this paper, we propose an efficient and simple rigid-fluid coupling scheme with scientific programming algorithms for particle-based fluid simulation and three-dimensional visualization. Our approach samples the surface of rigid bodies with boundary particles that interact with fluids. It contains two procedures, that is, surface sampling and sampling relaxation, which insures uniform distribution of particles with less iterations. Furthermore, we present a rigid-fluid coupling scheme integrating individual time stepping to rigid-fluid coupling, which gains an obvious speedup compared to previous method. The experimental results demonstrate the effectiveness of our approach.

Simulation-based Serious Games for Science Education and teacher assessment

This paper presents serious games developed for the science subject in elementary and middle schools, specifically on the three topics of “Force and Motion,” “State Change of Water,” and “Earth and Moon.” The PC game “Force and Motion” implemented frictional/gravitational/magnetic force simulations, in the mobile game “State Change of Water,” particle-based fluid simulations were implemented, and in the PC- and mobile-based multi-platform game “Earth and Moon,” a solar system simulation was implemented. In order to find out the essential components for the science educational games, the components of each topic were thoroughly analyzed, and then a game-based curriculum was developed for the components classified as having high- or mid-level difficulties in both teaching and learning. Based on the curriculum, the three games were created. The games were evaluated by elementary and middle school teachers, and the evaluation results showed that simulation-based serious games are promising tools for improving learning effects in science-related subjects.

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.

An evaluation of noise reduction algorithms for particle-based fluid simulations in multi-scale applications

Filtering of particle-based simulation data can lead to reduced computational costs and enable more efficient information transfer in multi-scale modelling. This paper compares the effectiveness of various signal processing methods to reduce numerical noise and capture the structures of nano-flow systems. In addition, a novel combination of these algorithms is introduced, showing the potential of hybrid strategies to improve further the de-noising performance for time-dependent measurements. The methods were tested on velocity and density fields, obtained from simulations performed with molecular dynamics and dissipative particle dynamics. Comparisons between the algorithms are given in terms of performance, quality of the results and sensitivity to the choice of input parameters. The results provide useful insights on strategies for the analysis of particle-based data and the reduction of computational costs in obtaining ensemble solutions.

A novel coupling of noise reduction algorithms for particle flow simulations

Proper orthogonal decomposition (POD) and its extension based on time-windows have been shown to greatly improve the effectiveness of recovering smooth ensemble solutions from noisy particle data. However, to successfully de-noise any molecular system, a large number of measurements still need to be provided. In order to achieve a better efficiency in processing time-dependent fields, we have combined POD with a well-established signal processing technique, wavelet-based thresholding. In this novel hybrid procedure, the wavelet filtering is applied within the POD domain and referred to as WAVinPOD. The algorithm exhibits promising results when applied to both synthetically generated signals and particle data. In this work, the simulations compare the performance of our new approach with standard POD or wavelet analysis in extracting smooth profiles from noisy velocity and density fields. Numerical examples include molecular dynamics and dissipative particle dynamics simulations of unsteady force- and shear-driven liquid flows, as well as phase separation phenomenon. Simulation results confirm that WAVinPOD preserves the dimensionality reduction obtained using POD, while improving its filtering properties through the sparse representation of data in wavelet basis. This paper shows that WAVinPOD outperforms the other estimators for both synthetically generated signals and particle-based measurements, achieving a higher signal-to-noise ratio from a smaller number of samples. The new filtering methodology offers significant computational savings, particularly for multi-scale applications seeking to couple continuum informations with atomistic models. It is the first time that a rigorous analysis has compared de-noising techniques for particle-based fluid simulations.

Numerical simulations of sloshing flows with elastic baffles by using a particle-based fluid–structure interaction analysis method

Sloshing flows in rolling tanks with elastic baffles are simulated using a modified particle-based fluid–structure interaction (FSI) solver. The modifications correspond to a newly proposed scheme for calculation of the fluid force on structure, and incorporation of a previously developed free-surface assessment scheme in the fluid model. To verify the fluid model, a violent sloshing flow is simulated and the results are compared with the related experimental data (Delorme et al., 2009) both qualitatively and quantitatively. Then, the FSI solver is applied to a comprehensive set of experiments of sloshing flow with elastic baffles (Idelsohn et al., 2008). The effects of baffles on the sloshing phenomena are studied by performing simulations corresponding to without any baffle, a rigid baffle and a set of flexible baffles.

Fabrication of dopamine grafted polyaniline/carbonyl iron core-shell typed microspheres and their magnetorheology

Abstract Magneto-responsive polyaniline (PANI)-coated magnetic carbonyl iron (CI) microspheres were synthesised using a dispersion polymerisation process. The CI particles were initially modified using dopamine as a chemical grafting agent to strengthen the affinity between PANI and the CI particles. The surface morphology of the fabricated core-shell structured particles was confirmed by scanning electron microscopy. The chemical composition of the dopamine-modified CI particles was examined by X-ray energy dispersive spectroscopy, and the magnetic properties of the particles were analysed using a vibrating sample magnetometer. The magnetorheological (MR) characteristics of the CI-PANI particle-based MR fluid dispersed in silicone oil were measured using a rotational rheometer, which exhibited a typical liquid-like to solid-like phase transition. The sedimentation stability of the microspheres was analysed further using a Turbiscan apparatus with better dispersion stability than pure CI particles.

Adaptively constructing liquid surface from particle-based simulation

Natural phenomena simulation attracts a lot of research attention and interest in virtual reality. The simulation for liquid has become a research focus in both computer graphics and computational physics, because of the difficulties in dynamic modelling and high computational complexity. We introduce the main research achievements in recent years with regard to liquids, which is a common natural phenomenon. A hybrid modelling approach for dynamic liquid simulation is proposed, followed by a surface reconstruction method using simulated results. In particle-based fluid simulation, surface construction is one procedure to contour the implicit function which determines an isosurface in a scalar field. We describe an adaptive polygonisation approach, by adaptively constructing an unconstrained octree structure, to reduce excessive subdivision which is required by traditional methods like Marching Cubes. Dual Marching Cubes is then applied to perform surface extraction on a new grid which is topologically dual to the octree structure. Experiment shows the advantages of our approach in generating satisfactory effects without excessively fine-grained grid structure. Satisfactory visual effect is achieved and this application can be used in computer games, movie making and virtual simulation in medical areas.

Efficient extracting surfaces approach employing anisotropic kernels for SPH fluids

Particles are disordered throughout the entire process of fluid simulation using particle-based methods, extracting surfaces through following up particles is unlikely to achieve. Therefore, it is reasonably necessary to extract fluid surfaces called surface reconstruction which has been research focus in particle-based fluid simulation for decades. To construct more smooth surfaces and enhance reconstruction efficiency in fluid simulation, this paper addresses an efficient anisotropic surface reconstruction method for particle-based fluid simulation. First, we simplify and modify the construction of traditional anisotropic kernel function. Second, we divide particles into near-surface particles and internal particles according to the analysis of particles’ eigenvectors. Finally, near-surface particles are involved in the calculation of surface reconstruction while internal particles are directly assigned color field values through the number of neighbor particles. Experimental results show that this algorithm ensures smoothness and geometric characteristics of fluid surfaces reconstructed. Compared to existing algorithms, this approach is simple and easy to implement and greatly improves the operation efficiency.

Surface turbulence for particle-based liquid simulations

We present a method to increase the apparent resolution of particle-based liquid simulations. Our method first outputs a dense, temporally coherent, regularized point set from a coarse particle-based liquid simulation. We then apply a surface-only Lagrangian wave simulation to this high-resolution point set. We develop novel methods for seeding and simulating waves over surface points, and use them to generate high-resolution details. We avoid error-prone surface mesh processing, and robustly propagate waves without the need for explicit connectivity information. Our seeding strategy combines a robust curvature evaluation with multiple bands of seeding oscillators, injects waves with arbitrarily fine-scale structures, and properly handles obstacle boundaries. We generate detailed fluid surfaces from coarse simulations as an independent post-process that can be applied to most particle-based fluid solvers.

쿨롱-모어 이론을 이용한 강탄성 반유동체 폭발 시뮬레이션

Unlike simulating general 'particle-based fluid explosion', simulating fluid with elasticity requires various experimental methods in order to show the realistic deformation of the matter. The existing studies on particle-based viscoelastic fluid only focused on matters' plastic deformation which can be found in mud or paint, based on the maximum distortion energy theory and maximum shear stress theory. However, these former researches could not simulate the brittle deformation which can be seen from silicon or highly elastic rubber when great external forces above limits are applied. This study suggests a brittle simulation method based on the Coulomb-Mohr theory, the idea that a yield occurs when maximum stress on a matter reaches to its rupture stress. This theory has a significant difference from the existing particle-based simulations which measures the forces on a matter by length or volume. Using a strong-elastic semifluid which Coulomb-Mohr theory is applied, realistic deformation process of a matter was observed as its forced surface reached to the rupture stress. When semifluid hit the ground, the impact of deformation can be explained by using Coulomb-Mohr theory.

A NUMERICALLY CONSISTENT MULTIPHASE POISEUILLE FLOW COMPUTATION BY A NEW PARTICLE METHOD

Recently, there is a rising interest in simulating fluid flow by using particle methods, which are mesh-free. However, the viscous stresses (or diffusion term) appeared in fluid flow governing equations are commonly expressed as the second-order derivatives of flow velocities, which are usually discretized by an inconsistent numerical approach in a particle-based method. In this work, a consistent method in discretizing the diffusion term is implemented in our particle-based fluid flow solver (namely the Moving Particle Pressure Mesh (MPPM) method). The new solver is then used to solve a multiphase Poiseuille flow problem. The error is decreasing while the grid is refined, showing the consistency of our current numerical implementation.

Particle-based parallel fluid simulation in three-dimensional scene with implicit surfaces

We propose an algorithm for fluid simulation in three-dimensional scenes with obstacles represented as implicit surfaces. The fluid simulation is performed based on the smoothed particle hydrodynamics method and the behavior of fluid particles in the vicinity of obstacles is defined by introducing a new model of particle motion specific to implicitly representation. For effective parallelization on the graphics processing units, we apply the grid of polynomial method to express the implicitly defined obstacles. The proposed method takes advantage of the properties of implicit representation such as smoothness, shape modelling and the expression of deforming objects.

Moving particle semi-implicit method for fluid simulation with implicitly defined obstacles

We developed a particle-based fluid simulation method with obstacles defined in implicit form. Our fluid simulation is based on the Moving Particle Semi-implicit (MPS) method, a typical particle-based algorithm achieving incompressible flow. In general, the particle-based fluid simulation is performed with obstacles that are defined as a set of particles located along the boundaries. We employ the implicit representation for the geometric information of obstacles which requires a new formulation of particle motion at the vicinity of boundaries. The main difficulty of MPS-based simulation with implicit obstacles is the lack of boundary particles that are required for the computation of two quantities: particle number density and particle force determined by pressure field. In our formulation, new definitions of the two quantities giving good estimation of the original ones is developed and incorporated in the MPS algorithm. In addition, we provide a modified algorithm for the construction of discrete linear system specific to the implicit representation for the computation of particle pressure. Our numerical tests show that the proposed approximation techniques provide adequate particle motion at the vicinity of the implicitly defined obstacles.

이상적인 점탄성체 항복 조건을 이용한 폭발 시뮬레이션

In particle-based fluid simulation, the yield stress is required for the deformation of the viscoelastic material like gel. von Mises's yield condition has been proposed to implement deformation of viscoelastic objects, but did not express the explosion. Furthermore, von Mises's yield condition is hard to approximate. We propose an ideal yield condition for viscoelastic object that reference from Tresca's yield condition. Unlike conventional particle-based simulation approximate the external power by the deformed length of the object, this paper is approximate the external power by area of the object. We check up that explosion was realistic when a viscoelastic object is compressed under the ideal yield condition.