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To investigate the energy-saving advantages of truck platoons, this study focused on two, three, and six-axle trucks as research subjects. A non-uniform platoon model of trucks was constructed based on braking performance differences. The aerodynamic characteristics of the non-uniform platoon fleet were analyzed in depth using numerical simulation methods, and the fuel consumption rate of the fleet was calculated. In a heterogeneous three-vehicle platoon, the 3-2-6 platooning approach exhibited the most effective reduction in fuel consumption, whereas the 3-6-2 platooning approach was the least effective. For a four-vehicle heterogeneous platoon comprising a three-axle truck, a six-axle truck, and two two-axle trucks, the 3-2-2-6 platooning approach yielded the best fuel efficiency. In a four-vehicle heterogeneous platoon with a two-axle truck, a six-axle truck, and two three-axle trucks, the 3-2-3-6 platooning approach proved to be the most effective in reducing fuel consumption. In a four-vehicle heterogeneous fleet composed of two-axle trucks, three-axle trucks, and two six-axle trucks, the 3-2-6-6 platooning approach achieved the best fuel efficiency. The conclusions of this study offer a fundamental scheme for truck formation, laying a crucial theoretical foundation for energy conservation and emissions reduction in transport systems. [ABSTRACT FROM AUTHOR]

Physics-based fluid simulation has played an increasingly important role in the computer graphics community. Recent methods in this area have greatly improved the generation of complex visual effects and its computational efficiency. Novel techniques have emerged to deal with complex boundaries, multiphase fluids, gas–liquid interfaces, and fine details. The parallel use of machine learning, image processing, and fluid control technologies has brought many interesting and novel research perspectives. In this survey, we provide an introduction to theoretical concepts underpinning physics-based fluid simulation and their practical implementation, with the aim for it to serve as a guide for both newcomers and seasoned researchers to explore the field of physics-based fluid simulation, with a focus on developments in the last decade. Driven by the distribution of recent publications in the field, we structure our survey to cover physical background; discretization approaches; computational methods that address scalability; fluid interactions with other materials and interfaces; and methods for expressive aspects of surface detail and control. From a practical perspective, we give an overview of existing implementations available for the above methods. [ABSTRACT FROM AUTHOR]

Membrane separation technology is one of the most widely studied methods for wastewater treatment. This paper is based on the non-solvent-induced phase separation (NIPS) method, which is combined with phase-field simulation to develop a fluid model for the volume fraction of tetrameric polyvinylidene fluoride (PVDF).In this paper, DMSO, DMAc and DMF are used as solvents, and pure water is used as a gel bath to simulate the relevant parameters of PVDF membrane; and PVP and LiCl are used as additives, and DMF and DMAc are used as solvents for the two-by-two combinations, and by calculating the relevant parameters of the PVDF quaternary membrane system, comparing and verifying the simulation results through experiments. results show that: the different solvents on the PVDF membrane in the order of DMSO > DMAc > DMF; additive LiCl system, the polymer diffusion rate in the polymer solution layer are faster than the PVP system. However, the top layer of the polymer solution layer in the PVP system is relatively flat, while the top layer of the polymer solution layer in the additive LiCl system is more undulating or even broken, indicating that LiCl has a greater influence on the membrane than PVP. [ABSTRACT FROM AUTHOR]

Aiming at the problem that inserting a needle into the abdomen of spindle-shaped fish can easily damage the internal organs during vaccine injection, this paper takes grass carp as the experimental object and designs a fry adsorption injection device. Through theoretical analysis, the key factors affecting the adsorption force are determined. The internal cavity of the adsorption block is simulated and optimized under the given boundary conditions. The single-factor test shows that the H-shaped suction head has the best adsorption effect. Further orthogonal experiments found that the height of the adsorption port, the adsorption port's length, and the diameter of the adsorption port are important factors that affect the test results, and they are arranged in descending order of their importance. The optimal parameter combination is the adsorption port height of 3 mm, adsorption port length of 15 mm, and adsorption pore diameter of 3 mm. Under these parameters, the success rate of needle insertion is 98%, and the survival rate of fry is 100%, which can meet the production requirements. In summary, the adsorption and injection device is simple in design, easy to operate, and can significantly reduce the damage to the fish body. It provides an effective solution and design reference for fish vaccination. [ABSTRACT FROM AUTHOR]

Because of the lack of good seedling positioning during vegetable grafting, there are issues such as high labor costs and long grafting time. This article proposes a negative pressure suction seedling positioning method for seed leaves based on the characteristic parameters of cucumber spike wood, and designs a flexible adsorption positioning mechanism for spike wood. Firstly, the ventral surface curve trajectories of cucumber cotyledons were extracted using Matlab software, and then a shape-adaptive design was applied to the attachment surface of the flexible suction positioning mechanism, and a computational fluid dynamics model of the airflow field was established. By combining Fluent simulation analysis with orthogonal experiments, the effect of suction hole diameter, vacuum negative pressure value, suction hole quantity, and suction hole depth on the adsorption effect of the suction head was analyzed, the main and secondary factors and operational indicators that affect the adsorption effect are evaluated. The optimal parameter combination: suction hole diameter of 1.5 mm, vacuum negative pressure value of 2 kPa, suction hole quantity of 42, and suction hole depth of 2 mm, has been found. A verification experiment was conducted on a test bench, and the experimental results show that the success rate of leaf absorption using the optimal parameter combination is 97.69%, which indicates that the suction head is designed reasonably and meets the requirements of grafting. [ABSTRACT FROM AUTHOR]

An atmospheric pressure jet that effectively prevents inner wall deposition has been developed, and its precursor distribution and thin-film deposition characteristics have been studied. The laser scattering and fluid simulation results show that the precursor (C4H10Zn) flow out of the eight holes of the central electrode and diffuse into the discharge region. Under the action of a discharge gas (Ar) of 2 slm is blown out of the plasma jet device, and will not diffuse to the inner wall of the plasma jet device. The optical photographs of the discharge show that the site of the monomer cleavage is about 1 mm closest to the inner wall of the jet device. With optical emission spectra (OES), a large number of characteristic emission peaks of Zn and CH were detected. The pattern of the deposited film closely resembles the diffusion pattern of the precursor within the plasma jet apparatus. By investigating deposited films in different regions, the influence of precursor distribution on film morphology and composition has been studied. XPS detected films near (black film) and far (white film) from the central region, and the results showed that films near the central region contained more organic components. This plasma device offers a stable plasma plume for thin film deposition and nanoparticle preparation. [ABSTRACT FROM AUTHOR]

When utilizing electrical discharge machining (EDM) for processing, the processing efficiency and quality will be significantly impacted, if the electrocorrosion residues in the gap flow field cannot be discharged in time. Numerical simulation is considered an effective means to simulate the flow field of EDM gaps. Based on simulation, this study investigates the processing time, depth, current, and dielectric (kerosene, water, and sunflower seed oil), on the movement of electrocorrosion residues within the dielectric. The simulation results demonstrate that an increase in processing time, current, or depth leads to a decrease in the escape rate of corrosion residues from the discharge gap. Compared with kerosene and sunflower seed oil, water has a higher residue escape rate, but the actual processing effect is not ideal. The escape rate of sunflower seed oil at any time was higher than that of kerosene,the highest was higher than 25%, and the average was higher than 22.21%. Sunflower seed oil can be used as a renewable dielectric to replace kerosene. Subsequently, verification experiments are conducted based on simulation results that demonstrate that the discrete phase model (DPM) fluid simulation exhibits excellent coupling with actual processing conditions. [ABSTRACT FROM AUTHOR]

The use of particles-based simulations to produce fluid animations is nowadays a frequently used method by both the industrial and research sectors. Although there are many variations of the smoothed particle hydrodynamics (SPH) algorithm currently being used, they all have the common characteristic of being highly parallel in nature. They are therefore frequently implemented on graphics processing units (GPUs) to benefit of high computation capacities of modern GPUs. However, such optimizations require specific optimizations to make use of the full capacity of the GPU, with sometimes optimizations being contradictory to optimizations used in CPU implementations. In this paper, we explored various optimizations on a GPU implementation of a recent particle-based fluid simulation algorithm using an iterative pressure solver. In particular, we focused on CPU optimizations that have not been thoroughly studied for GPU implementations: the indexing for the neighbor's structure, the frequency of the sorting of the fluid particles, the use of lookup tables for the kernel function computations and the use of a warm-start to improve the performance of the iterative pressure solver. We show that some of these optimizations are only effective for very specific hardware configurations and sometimes even impact the performance negatively. We also show that the warm-start reduces the computation time but introduces a cyclic instability in the simulation. We propose a solution to reduce this instability without requiring to modify the implementation of the fluid algorithm. [ABSTRACT FROM AUTHOR]

In classical smoothed particle hydrodynamics (SPH) fluid simulation approaches, the smoothing length of Lagrangian particles is typically constant. One major disadvantage is the lack of adaptiveness, which may compromise accuracy in fluid regions such as splashes and surfaces. Attempts to address this problem used variable smoothing lengths. Yet the existing methods are computationally complex and non-efficient, because the smoothing length is typically calculated using iterative optimization. Here, we propose an efficient non-iterative SPH fluid simulation method with variable smoothing length (VSLSPH). VSLSPH correlates the smoothing length to the density change, and adaptively adjusts the smoothing length of particles with high accuracy and low computational cost, enabling large time steps. Our experimental results demonstrate the advantages of the VSLSPH approach in terms of its simulation accuracy and efficiency. [ABSTRACT FROM AUTHOR]

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Concentrated sulfuric acid dilution is an essential yet hazardous experiment in chemistry education. Incorrect operations can lead to intensive boiling and splattering or even endanger the experiment operator. This paper presents a novel approach to simulate the violent boiling phenomenon in real time and an efficient method to deal with particle penetration caused by fast motion. We introduce the anti-viscosity method to inject momentum into high-temperature particles and capture the chaotic dynamics in the boiling process with small computational overhead. To address the particle penetration issue, we propose a new constraint type called flask constraint which uses radius lookup tables to represent axisymmetric shapes efficiently and projects the particles back into their container when penetration occurs. These methods are integrated into a virtual reality application to simulate the concentrated sulfuric acid dilution experiment and demonstrate the efficiency and effectiveness of our method. Our work improves the capability and stability of particle-based fluid solvers and provides appealing solutions for integrating fluid simulation into interactive applications. [ABSTRACT FROM AUTHOR]

We propose a new advection scheme for fluid simulation that improves both conservation and numerical diffusion. Our work differs from previous works in that we re-formulate interpolation as cell-face flux of a vector field instantly constructed from a scalar field, rather than a per-point evaluation at back-traced positions. Our novel interpolation method enables excellent preservation of conservative quantities since the sum of flux exactly counteracts on cell faces, which eventually evaluates the boundary-flux of the whole domain. Our method can be implemented as a plug-and-play extension (or a temporary scratchpad) to the conventional semi-Lagrangian scheme; hence, our method naturally inherits all the benefits of semi-Lagrangian schemes and can be seamlessly integrated with existing fluid simulation pipelines together with other (black-boxed) solver components. We conducted numerical experiments to verify the accuracy of our scheme (conservation and the improved numerical diffusion) and compared its qualitative results with state-of-the-art advection schemes that are in heavy use in the production environment such as MacCormack and the WENO6 interpolation. [ABSTRACT FROM AUTHOR]

We propose a novel turbulence refinement method based on the Rankine vortex model for smoothed particle hydrodynamics (SPH) simulations. Surface details are enhanced by recovering the energy lost due to the lack of the rotation of SPH particles. The Rankine vortex model is used to convert the diffused and stretched angular kinetic energy of particles to the linear kinetic energy of their neighbors. In previous vorticity-based refinement methods, adding more energy than required by the viscous damping effect leads to instability. In contrast, our model naturally prevents the positive feedback effect between the velocity and vorticity fields since the vortex model is designed to alter the velocity without introducing external sources. Experimental results show that our method can recover missing high-frequency details realistically and maintain convergence in both static and highly dynamic scenarios. [ABSTRACT FROM AUTHOR]

We present a novel surface reconstruction pipeline that significantly improves reconstructing efficiency while preserves high-quality details for particle-based liquid simulation. Our surface reconstruction algorithm is a sort of completely parallel narrow band method. At the beginning of reconstruction, we develop a spatial hashing grid-based strategy to identify surface particles, which is much more precise and simpler than the smoothed color field. Consequently, those precise surface particles ensure accurate extraction of scalar field in the narrow band around surface without any redundancy, which brings great performance improvement for subsequent reconstruction stages. Furthermore, in order to obtain a better computation performance, we carefully analyze the potential race conditions and conditional branches of each reconstruction step between parallel threads and come up with a completely parallel reconstruction method combined with the exclusive prefix sum algorithm. Our method is pretty straightforward to implement. Experimental results demonstrate that our method runs up to dozen times faster than the state-of-the-art of narrow band-based fluid surface reconstruction, especially for large-scale particle-based fluid. [ABSTRACT FROM AUTHOR]

The electron density distribution and average electron temperature distribution in reactive ion etching (RIE) chamber are of great significance for the ionization and excitation reaction rate. The uniformity of radial distributions of the electron density and average electron temperature in the discharge chamber greatly affects the uniformity of the etching, especially the plasma etching of large area SiO2 substrates. We study the effects of discharge conditions (including power and pressure) on the electron density and average electron temperature of plasma-etched 400 mm SiO2 substrates in the reactive ion etching chamber; the simulation results show that the allowable major discharge conditions strongly affect the characteristics of plasma in the large area reactive ion etching chamber. Specifically, with increase in the power both the electron density and average electron temperature increase, being accompanied by deteriorating uniformity of their radial distributions. As the pressure increases, the electron density increases but average electron temperature decreases, being accompanied by deteriorating uniformity of their radial distributions. These methods and conclusions can provide reference for the improvement of cavity structure and large area RIE equipment designing and selection of the process parameters. [ABSTRACT FROM AUTHOR]

Fluid simulation is a well-established research field in computer graphics that aims to generate realistic and visually appealing simulations of fluids, including water, smoke, and fire. Divergence is identified as a crucial factor in achieving realistic fluid behavior. This article presents a GPU optimization of the pointwise incompressible fluid simulation technique, which uses pointwise incompressible velocity interpolation to ensure divergence at arbitrary points, rather than grid cells. Pointwise incompressible velocity interpolation at arbitrary points is the curl of velocity potential. The velocity potential can be obtained from the divergence-free velocities by solving a Poisson equation. To enhance the computational efficiency of the simulation, an odd–even geometric multigrid method is introduced to solve Poisson’s equation on non-power-of-2 resolution grids. Additionally, to recover the potential on grid cells, a warp-level method is proposed via divergence-free velocities on grid cells. The proposed warp-level potential recovery method offers GPU optimization and enhanced efficiency, in contrast to the sweeping method that only provides CPU optimization for potential recovery. Furthermore, a locally enhanced method is proposed to recover the detailed velocity potential within small domains through the use of the odd–even multigrid. The experiments show that the odd–even multigrid outperforms Weber’s multigrid by an average speedup factor of 4.32 across various grid sizes. On the other hand, the warp-level potential recovery method demonstrates notable speedups ranging from approximately 2–6 times for 2D grids and about 1.35–2.64 times for 3D grids when compared to the parallel sweeping method on GPU. The results of these contributions demonstrate remarkable improvements in the efficiency and performance of fluid simulations in computer graphics, harnessing the computational capabilities of modern GPUs to achieve visually appealing and realistic fluid behaviors. [ABSTRACT FROM AUTHOR]

Incompressible SPH (ISPH) is a promising concept for the pressure computation in SPH. It works with large timesteps and the underlying pressure Poisson equation (PPE) can be solved very efficiently. Still, various aspects of current ISPH formulations can be optimized. This paper discusses issues of the two standard source terms that are typically employed in PPEs, i.e., density invariance (DI) and velocity divergence (VD). We show that the DI source term suffers from significant artificial viscosity, while the VD source term suffers from particle disorder and volume loss. As a conclusion of these findings, we propose a novel source term handling. A first PPE is solved with the VD source term to compute a divergence-free velocity field with minimized artificial viscosity. To address the resulting volume error and particle disorder, a second PPE is solved to improve the sampling quality. The result of the second PPE is used for a particle shift (PS) only. The divergence-free velocity field—computed from the first PPE—is not changed, but only resampled at the updated particle positions. Thus, the proposed source term handling incorporates velocity divergence and particle shift (VD + PS). The proposed VD + PS variant does not only improve the quality of the computed velocity field, but also accelerates the performance of the ISPH pressure computation. This is illustrated for IISPH—a recent ISPH implementation—where a performance gain factor of 1.6 could be achieved. [ABSTRACT FROM AUTHOR]

We introduce a new advection scheme for fluid animation. Our main contribution is the use of long-term temporal changes in pressure to extend the commonly used semi-Lagrangian scheme further back along the time axis. Our algorithm starts by tracing sample points along a trajectory following the velocity field backwards in time for many steps. During this backtracing process, the pressure gradient along the path is integrated to correct the velocity of the current time step. We show that our method effectively suppresses numerical diffusion, retains small-scale vorticity, and provides better long-term kinetic energy preservation. [ABSTRACT FROM AUTHOR]

Hybrid approaches such as combining video data with pure physics-based simulation have been popular in the recent decade for computer graphics. The key motivation is to clearly retain salient advantages from both data-driven method and model-centric numerical simulation, while overcoming certain difficulties of both. The Eulerian method, which has been widely employed in flow simulation, stores variables such as velocity and density on regular Cartesian grids, thereby it could be associated with (volumetric) video data on the same domain. This paper proposes a novel method for flow simulation, which is tightly coupling video-based reconstruction with physically-based simulation and making use of meaningful physical attributes during re-simulation. First, we reconstruct the density field from a single-view video. Second, we estimate the velocity field using the reconstructed density field as prior. In the iterative process, the pressure projection can be treated as a physical constraint and the results of each step are corrected by obtained velocity field in the Eulerian framework. Third, we use the reconstructed density field and velocity field to guide the Eulerian simulation with anticipated new results. Through the guidance of video data, we can produce new flows that closely match with the real scene exhibited in data acquisition. Moreover, in the multigrid Eulerian simulation, we can generate new visual effects which cannot be created from raw video acquisition, with a goal of easily producing many more visually interesting results and respecting true physical attributes at the same time. We demonstrate salient advantages of our hybrid method with a variety of animation examples. [ABSTRACT FROM AUTHOR]

We present a novel adaptive stepping scheme for SPH fluids, in which particles have their own time steps determined from local conditions, e.g. courant condition. These individual time steps are constrained for global convergence and stability. Fluid particles are then updated asynchronously. The approach naturally allocates computing resources to visually complex regions, e.g. regions with intense collisions, thereby reducing the overall computational time. The experiments show that our approach is more efficient than the standard method and the method with globally adaptive time steps, especially in highly dynamic scenes. [ABSTRACT FROM AUTHOR]

Fast and vivid fluid simulation and visualization is a challenge topic of study in recent years. Particle-based simulation method has been widely used in the art animation modeling and multimedia field. However, the requirements of huge numerical calculation and high quality of visualization usually result in a poor computing efficiency. In this work, in order to improve those issues, we present a fast framework for 3D fluid fast constructing and visualization which parallelizes the fluid algorithm based on the GPU computing framework and designs a direct surface visualization method for particle-based fluid data such as WCSPH, IISPH, and PCISPH. Considering on conventional polygonization or adaptive mesh methods may incur high computing costs and detail losses, an improved particle-based method is provided for real-time fluid surface rendering with the screen-space technology and the utilities of the modern graphics hardware to achieve the high performance rendering; meanwhile, it effectively protects fluid details. Furthermore, to realize the fast construction of scenes, an optimized design of parallel framework and interface is also discussed in our paper. Our method is convenient to enforce, and the results demonstrate a significant improvement in the performance and efficiency by being compared with several examples. [ABSTRACT FROM AUTHOR]

In order to capture stable and realistic microscopic features of fluid surface, a surface tension and adhesion method based on implicit incompressible SPH (smoothed particle hydrodynamics) is presented in this paper. It gives a steady and fast tension model and can solve the problem of not considering adhesion. Molecular cohesion and surface minimization are considered for surface tension, and adhesion is added to show the microscopic characteristics of the surface. To simulate surface tension and adhesion stably and efficiently, the surface tension and adhesion model is integrated to an implicit incompressible SPH method. The experimental results show that the method can better simulate surface features in a variety of scenarios compared with previous methods and meanwhile ensure stability and efficiency. [ABSTRACT FROM AUTHOR]

We present a methodology about real-time 3D fluid simulation system using BCI (brain-computer interface). Spectators appreciate our work with their emotion. The advance of technology has exerted huge impacts on arts and as result a new genre called digital art has emerged. In digital art, interaction is an important element. Various types of interaction are bein g implemented in digital art using touch, hand gesture, sound, movement, etc., even brain wave. Usually, digital artists pursue interactions in their art work; the reason is that they want spectators' deep appreciation and involvement. However, many of interactive digital art works fail to induce interaction as much as the artists expected. If visible interaction is weak, or interaction result is weak, spectators are not immersed much in the work. Nowadays, there are many interactive digital arts. In digital art, new type of interaction is needed to captivate spectators. So, we tried to implement BCI interaction digital art prototype (tentative title: Soul flow). Electroencephalography (EEG) is the recording of brain electrical activity along the scalp. We measured user's EEG signal using MindSet (the MindSet senses EEG brainwave data to power the innovation of laboratory researchers and application developers like no other EEG device in the world. It delivers RAW signal, power frequency bands and NeuroSky eSense meters:attention, meditation. ) to take user's emotional state on appreciating digital art. We can get user's emotional state in four categories (attention/inattention, meditation/uneasiness) and these emotional states interact with 3D fluid simulation system in real-time. In this art work prototype, each spectator experiences each different fluid (scale, speed and visual) because each spectator has different emotional state. Our art work prototype expressed the flow through water flow simulation. Flow means the mental state of operation in which a person performing an activity is fully immersed in a feeling of energized focus, full involvement, and enjoyment in the process of the activity. In essence, flow is characterized by complete absorption in what one does (The psychology of optimal experience 1990). In addition, it means stream in water flow. We pursued these concepts and expressed to 3D fluid simulation digital art using BCI. We used Unity3D and MindSet to implement our art work prototype. This study will expand the participation of the spectator in digital art. In addition, it will expand the possibilities of BCI in digital art interaction. [ABSTRACT FROM AUTHOR]

Surface tension plays a significant role in fluid simulation, especially small-scale fluid. In this paper, we present a novel surface tension formulation for smoothed particle hydrodynamics (SPH) to simulate interfacial fluid flow. The surface tension formulation is decomposed into three main processes: (1) volume-preserved mesh smoothing, (2) surface tension computation and (3) surface tension transfer. Firstly, we exploit a Lagrangian operator to smooth an initial three-dimensional discrete interfacial surface mesh generated from fluid particles; and then the surface mesh is scaled in a volume-preserved way and the center is translated to its original position to get a smoothed mesh. Secondly, surface tension strengths on the vertices of the interfacial surface mesh are computed according to the offsets from the original surface mesh to the smoothed mesh. Finally, we transfer the surface tension strengths from the mesh vertices onto their neighbor fluid particles in a conservative way. The proposed surface tension solver is simple and straightforward to be plugged into a standard SPH solver. Experimental results show that it is effective and efficient to produce realistic fluid simulations, especially for the phenomena with strong surface tension. [ABSTRACT FROM AUTHOR]

Through-mask electrochemical machining has been shown to be very feasible for machining metal parts with hole arrays. However, machining a large-area hole array by through-mask electrochemical machining has been challenging. To machine a large-area hole array, in this paper, a serpentine flow channel is proposed for through-mask electrochemical machining. The principle of the serpentine flow channel is introduced. Computational fluid dynamic simulations show that the flow state in the channel is not uniform. To deal with this problem, circular deflectors are placed in the corners of the channel. By adjusting the circular deflectors, an optimal serpentine flow channel is obtained with a steady flow state. This optimal channel is used in a through-mask electrochemical machining experiment, and a 10 × 20 hole array with 2.564-mm average diameter is fabricated. The maximum deviation of diameters is 0.04 mm, and the roundness is less than 8 μm in this hole array. [ABSTRACT FROM AUTHOR]

This paper introduces a novel workflow to generate snow imprints, and model the interaction of snow with dynamic objects. We decoupled snow simulation into three components: a base layer, snow particles, and snow mist. The base layer consists of snow that has not been in contact with a dynamic object yet, and is stored as a level set. Snow particles model the interaction between the snow and the dynamic objects. They are added when the dynamic objects collide with the base layer, and are animated using an adapted granular material simulation. The very thin and powdery snow released by airborne snow particles is modeled by the snow mist. This component is greatly influenced by the surrounding air medium; thus, it is animated using a fluid simulation. This decomposition allows to focus memory expensive and time-consuming computations only where dynamic objects interact with the snow, which is much more efficient than relying on a full-scale simulation. [ABSTRACT FROM AUTHOR]

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. Graphical Abstract: [ABSTRACT FROM AUTHOR]

We propose a particle-based hybrid method for simulating volume preserving viscoelastic fluids with large deformations. Our method combines smoothed particle hydrodynamics (SPH) and position-based dynamics (PBD) to approximate the dynamics of viscoelastic fluids. While preserving their volumes using SPH, we exploit an idea of PBD and correct particle velocities for viscoelastic effects not to negatively affect volume preservation of materials. To correct particle velocities and simulate viscoelastic fluids, we use connections between particles which are adaptively generated and deleted based on the positional relations of the particles. Additionally, we weaken the effect of velocity corrections to address plastic deformations of materials. For one-way and two-way fluid-solid coupling, we incorporate solid boundary particles into our algorithm. Several examples demonstrate that our hybrid method can sufficiently preserve fluid volumes and robustly and plausibly generate a variety of viscoelastic behaviors, such as splitting and merging, large deformations, and Barus effect. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In this paper, we present a new numerical method for advection in fluid simulation. The method is built on the Characteristic Mapping method. Advection is solved via grid mapping function. The mapping function is maintained with higher order accuracy BFECC method and dynamically reset to identity mapping whenever an error criterion is met. Dealing with mapping function in such a way results in a more accurate mapping function and more details can be captured easily with this mapping function. Our error criterion also allows one to control the level of details of fluid simulation by simply adjusting one parameter. Details of implementation of our method are discussed and we present several techniques for improving its efficiency. Both quantitative and visual experiments were performed to test our method. The results show that our method brings significant improvement in accuracy and is efficient in capturing fluid details. [ABSTRACT FROM AUTHOR]

We present a particle-based method to simulate and visualize the interaction of knitwear with fluids. The knitwear is modeled using spring-mass systems and the fluid is modeled using the smoothed particle hydrodynamics method. Two-way coupling is achieved by considering surface tension, capillary, and interparticle forces between the fluid and knitwear. The simulation of fluid and knitwear particles is performed on the graphics processing unit. Photorealistic rendering of knitwear and fluid is achieved by using a hardware-accelerated rasterization-based rendering technique. Our method is able to simulate and visualize the macro- and microstructure of free-form knitwear and reflective and refractive characteristics of the fluid surface. [ABSTRACT FROM AUTHOR]

A detailed description of turbulent fluids based on numerical simulation is an important research topic required by many visual effects. We propose a novel method to simulate fluids with turbulent small-scale details. By inserting diffusive derivatives and divergence-free constraints to moving least-squares (MLS) fitting, we upgrade the velocity interpolation method for existing fluid solvers to enhance the subgrid accuracy. The time-step restriction of asymptotic property of diffusive derivatives is resolved by means of coupling to the constrained interpolation profile (CIP) advection framework. The proposed constrained moving least-squares interpolation profile (CMIP) method provides intuitive control over turbulence through the adjustment of one parameter as though controlling the Reynolds number with an inviscid model. The proposed method generates improved visuals of the highly turbulent fluid and is complementary to existing techniques that are currently being used. [ABSTRACT FROM AUTHOR]

We present a new real-time image marbleization method that converts an image into a marble-like appearance automatically. The approach models the marbleization process as a two-dimensional fluid dynamics problem, whereby color advection of an input image results in a marbleized image. During the fluid dynamics simulation, we add a pixel-level external force field which is tangent to salient features in the image. The forces are computed from the image characteristics without user intervention. A stylized image with marble-like appearance is easily created that maintains the basic shape of objects in the input image. The entire modeling framework is implemented on a graphics processing unit, thus enabling real-time visual feedback. This approach provides a new tool to design figurative marbling textures without mixing of colors, which are almost impossible with previous computer-generated marbling methods. [ABSTRACT FROM AUTHOR]

Ultraprecise optical elements are applied in advanced optical apparatus. Elastic emission machining (EEM) is one of the ultraprecision machining methods used to fabricate shapes with 0.1-nm accuracy. In this study, we proposed and experimentally tested the control of the shape of a stationary spot profile by introducing a focusing-flow state between the nozzle outlet and the workpiece surface in EEM. The simulation results indicate that the focusing-flow nozzle sharpens the distribution of the velocity on the workpiece surface. The results of machining experiments verified those of the simulation. The obtained stationary spot conditions will be useful for surface processing with a high spatial resolution. [ABSTRACT FROM AUTHOR]

Physically based fluid simulation in recent years has been successful for small-scale fluids such as liquid in a cubic cavity. However, for boundless free-surface flow of large scale and irregular area, there is a critical trade-off between simulation efficiency and accuracy because of the restriction of the traditional regular computational grids. This paper introduces boundless computational grids based on hierarchical runlength encoding to simulate large-scale free-surface flow. We first modeled the free-surface flow with a lattice Boltzmann method, and calculated the surface curvature in the update process. We then introduced an effective method with which to calculate the surface curvature according to the surface tension so that the surface detail was enhanced, and obtained the curvature of each surface effectively as it was extracted. Furthermore, we dynamically compressed and indexed the computational cells with the improved hierarchical run-length encoding algorithm, so that the grid expands dynamically according to the fluid flow and the computational resources used were proportional to the volume of the fluid. Finally fluids in different situations were simulated realistically. The proposed method makes the best of the computational resources to perform the simulation with high resolution, and dynamically allocates resources so that the fluid can expand in random directions without boundaries, which is suited to the simulation of large-scale visual scenes. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Fluid dynamics can produce realistic looking fire effects, which are heavily used in animation and films. However, the parameters of the various underlying physical equations are not intuitive enough to be controlled easily. As a result, animators face problems when editing the fine details of the fire, especially the turbulence and growth at the fire surface. In this paper, we propose a new approach to enable animators to interactively edit such fine details using textured forces. These techniques involve mapping a texture onto the simulation that controls the creation of new forces, growing the fire into specific shape and adding the natural turbulence of fuel ignition. These textures can be edited using an intuitive user interface that allows forces to be painted directly onto the fire. Our system can be integrated into existing GPU fluid solvers to run in real-time. As a result, it is applicable for interactive applications such as 3D computer games. [ABSTRACT FROM AUTHOR]

We propose a new fluid modeling technique aimed at incorporating stochastic turbulence into a widely used Lagrangian fluid solver, the Smoothed Particle Hydrodynamics (SPH) method. We add to each SPH particle a swirling probability to model its likelihood to act as a swirling incentive particle (SIP). Particles are selected as a SIP randomly based on the probability, and a SIP spins its neighboring particles to rotate around itself by applying rotational force. The force is computed from a swirling vorticity of the SIP. We model the production, development, and spreading of the swirling probability and vorticity among all SPH particles. The algorithm inherently implements preferred turbulence evolution including vortex aggregation and decay. The turbulent effects are non-repeating and easily controlled by animators. Our method is fully integrated with the SPH scheme with minimal extra memory usage, computational load, and programming efforts. [ABSTRACT FROM AUTHOR]

The existence of liquid water was found very important in incineration flue gas clean-up systems for enhancing the absorption of acid components contained. In a newly developed incineration flue gas clean-up tower, which works in a semi-dry mode, the water is injected in the form of spray to maximum its contact surface with the gas. The criteria for the design of the water nozzles would be high water concentration but no liquid impinging on the solid wall and complete evaporation inside the tower. In order to optimize the atomizer design, the effects of the spray type (hollow or solid cone), their initial droplet size distribution and water flow rate on the performance of the acid gas absorption were investigated. The liquid behaviour was studied with a fluid dynamic simulation code, and the overall performance was checked experimentally. This paper presents the use of a commercial CFD code, FLUENT, and some modifications made during such investigation. The modification includes the viscosity of the flue gas defined as a function of the temperature, and the initial mass fraction of different droplet size group described with an exponential distribution formula of Rosin-Rammler. The investigation results (the optimal spray parameters) were used to guide the water nozzle design. The general performance of the flue gas clean-up system measured during the plant operation complied with the design criteria. [ABSTRACT FROM AUTHOR]

The multigrid method is widely used in fluid simulation because of its strong convergence. In addition to operating accuracy, operational efficiency is also an important factor to consider in order to enable real-time fluid simulation in computer graphics. For this problem, we compared the performance of the Algebraic Multigrid and the Geometric Multigrid in the V-Cycle and Full-Cycle schemes respectively, and analyze the convergence and speed of different methods. All the calculations are done on the parallel computing of GPU in this paper. Finally, we experiment with the 3D-grid for each scale, and give the exact experimental results. [ABSTRACT FROM AUTHOR]