Energy-based dissolution simulation using SPH sampling

A novel unified particle-based method is proposed for real-time dissolution simulation that is fast, predictable, independent of sampling resolution, and visually plausible. The dissolution model is derived from collision theory and integrated into a smoothed particle hydrodynamics fluid solver. Dissolution occurs when a solute is submerged in solvent. Physical laws govern the local excitation of solute particles based on kinetic energy: when the local excitation energy exceeds a user-specified threshold (activation energy), the particle will be dislodged from the solid. Solute separation during dissolution is handled using a new Graphics Processing Unit (GPU)-based region growing method. The use of smoothed particle hydrodynamics sampling for both solute and solvent guarantees a predictable and smooth dissolution process and provides user control of the volume change during the phase transition. A mathematical relationship between the activation energy and dissolution time allows for intuitive artistic control over the global dissolution rate. We demonstrate this method using a number of practical examples, including antacid pills dissolving in water, hydraulic erosion of nonhomogeneous terrains, and melting

Energy based dissolution simulation using smoothed particle hydrodynamic sampling

Fluid simulation plays an important role in Computer Graphics and has wide applications in film and games. The desire for an improved physically-based fluid simulation solver has grown hand in hand with the advances made in Computer Graphics. Interesting fluid behaviours emerge when solid objects are added to a simulation: when fluid and solid make contact, they do not only have a physical interaction (e.g., buoyancy), but also a chemical reaction (e.g., dissolution) under the right conditions. Dissolution is one of the most common natural phenomena which is an important visual effect in fluid simulation. However this phe- nomenon is difficult to simulate due to the complexity of the behaviour and there are only few techniques available. A novel unified particle-based method for approximating chemical dis- solution is introduced in this thesis which is fast, predictable and visually plausible. The dissolution algorithm is derived using chemical Collision Theory and integrated into a Smoothed Particle Hydrodynamics (SPH) framework. The Collision Theory of chemistry is used as an analogy to the dissolution process modelling. Dissolution occurs when solute submerges into solvent. Physical laws govern the local excitation of so- lute particles based on the relative motion with solvent particles. When the local excitation energy exceeds a user specified threshold (activation energy), the particle will be dislodged from the solid. Unlike previous methods, this dissolution model ensures that the dissolution result is in- dependent of solute sampling resolution. A mathematical relationship is also established between the activation energy, the interfacial surface area, and the total dissolution time — allowing for intuitive artistic con- trol over the global dissolution rate. Applications of this method are demonstrated using a number of practical examples, including antacid pills dissolving in water and hydraulic erosion of non-homogeneous ter- rains. Both solutes and solvents are represented by particles, and the dis- tribution of the solute particles greatly affects the plausibility of the dissolution simulation. An even but stochastic distribution of particles on both the surface and within the volume of the solute is essential for a good visual simulation of the dynamic process of dissolution. A new iterative particle-based sampling method derived from SPH is introduced in this thesis which can generate a range of blue noise pat- terns and is computationally efficient, controllable and has a variety of applications. This approach resolves many of the limitations of classic blue noise methods, such as the lack of controllability or varying the dis- tribution properties of the generated samples. Fast sampling is achieved in general dimensions for curves, surfaces and volumes. By varying a sin- gle parameter, the proposed method can generate a range of controllable blue noise samples with different distribution properties which are suit- able for various applications such as adaptive sampling and multi-class sampling. The SPH sampling approach is used for solute particle distribution which guarantees a predictable and smooth dissolution process thanks to the evenly distributed density and also gives the user control of the volume change during the phase transition. The proposed SPH sampling method achieves better visual effects compared with simple grid sampling and other blue noise sampling methods. Our energy based dissolution simulation with SPH sampled solute and solvent ensures that the dissolution behaviour is physically and chemi- cally plausible, while supporting features such as object separation and sharp feature rounding. The simulation is parallelized per particle on a GPU to enhance the performance

A particle-based dissolution model using chemical collision energy

We propose a new energy-based method for real-time dissolution simulation. A unified particle representation is used for both fluid solvent and solid solute. We derive a novel dissolution model from the collision theory in chemical reactions: physical laws govern the local excitation of solid particles based on the relative motion of the fluid and solid. When the local excitation energy exceeds a user specified threshold (activation energy), the particle will be dislodged from the solid. Unlike previous methods, our model ensures that the dissolution result is independent of solute sampling resolution. We also establish a mathematical relationship between the activation energy, the inter-facial surface area, and the total dissolution time - allowing for accurate artistic control over the global dissolution rate while maintaining the physical plausibility of the simulation. We demonstrate applications of our method using a number of practical examples, including antacid pills dissolving in water and hydraulic erosion of non-homogeneous terrains. Our method is straightforward to incorporate with existing particle-based fluid simulations

Fast Multiple-Fluid Simulation Using Helmholtz Free Energy

Multiple-fluid interaction is an interesting and common visual phenomenon we often observe. In this paper, we present an energybased Lagrangian method that expands the capability of existing multiple-fluid methods to handle various phenomena, such as extraction, partial dissolution, etc. Based on our user-adjusted Helmholtz free energy functions, the simulated fluid evolves from high-energy states to low-energy states, allowing flexible capture of various mixing and unmixing processes. We also extend the original Cahn-Hilliard equation to be better able to simulate complex fluid-fluid interaction and rich visual phenomena such as motionrelated mixing and position based pattern. Our approach is easily integrated with existing state-of-the-art smooth particle hydrodynamic (SPH) solvers and can be further implemented on top of the position based dynamics (PBD) method, improving the stability and incompressibility of the fluid during Lagrangian simulation under large time steps. Performance analysis shows that our method is at least 4 times faster than the state-of-the-art multiple-fluid method. Examples are provided to demonstrate the new capability and effectiveness of our approach

Multiphase SPH simulation for interactive fluids and solids

This work extends existing multiphase-fluid SPH frameworks to cover solid phases, including deformable bodies and granular materials. In our extended multiphase SPH framework, the distribution and shapes of all phases, both fluids and solids, are uniformly represented by their volume fraction functions. The dynamics of the multiphase system is governed by conservation of mass and momentum within different phases. The behavior of individual phases and the interactions between them are represented by corresponding constitutive laws, which are functions of the volume fraction fields and the velocity fields. Our generalized multiphase SPH framework does not require separate equations for specific phases or tedious interface tracking. As the distribution, shape and motion of each phase is represented and resolved in the same way, the proposed approach is robust, efficient and easy to implement. Various simulation results are presented to demonstrate the capabilities of our new multiphase SPH framework, including deformable bodies, granular materials, interaction between multiple fluids and deformable solids, flow in porous media, and dissolution of deformable solids

The Star Cluster Population of the Collisional Ring Galaxy NGC 922

We present a detailed study of the star cluster population detected in the galaxy NGC922, one of the closest collisional ring galaxies known to date, using HST/WFPC2 UBVI photometry, population synthesis models, and N-body/SPH simulations.We find that 69% of the clusters are younger than 7Myr, and that most of them are located in the ring or along the bar, consistent with the strong Halpha emission. The cluster luminosity function slope of 2.1-2.3 for NGC922 is in agreement with those of young clusters in nearby galaxies. Models of the cluster age distribution match the observations best when cluster disruption is considered. We also find clusters with ages (>50Myr) and masses (>10^5 Msun) that are excellent progenitors for faint fuzzy clusters. The images also show a tidal plume pointing toward the companion. Its stellar age from our analysis is consistent with pre-existing stars that were stripped off during the passage of the companion. Finally, a comparison of the star-forming complexes observed in NGC922 with those of a distant ring galaxy from the GOODS field indicates very similar masses and sizes, suggesting similar origins.Comment: 17 pages including 13 figures. Accepted for publication in AJ. Full resolution version at http://people.physics.tamu.edu/pellerin/Pellerin_etal_NGC922.pd

A moving least square reproducing kernel particle method for unified multiphase continuum simulation

In physically based-based animation, pure particle methods are popular due to their simple data structure, easy implementation, and convenient parallelization. As a pure particle-based method and using Galerkin discretization, the Moving Least Square Reproducing Kernel Method (MLSRK) was developed in engineering computation as a general numerical tool for solving PDEs. The basic idea of Moving Least Square (MLS) has also been used in computer graphics to estimate deformation gradient for deformable solids. Based on these previous studies, we propose a multiphase MLSRK framework that animates complex and coupled fluids and solids in a unified manner. Specifically, we use the Cauchy momentum equation and phase field model to uniformly capture the momentum balance and phase evolution/interaction in a multiphase system, and systematically formulate the MLSRK discretization to support general multiphase constitutive models. A series of animation examples are presented to demonstrate the performance of our new multiphase MLSRK framework, including hyperelastic, elastoplastic, viscous, fracturing and multiphase coupling behaviours etc

Fluid Simulation by the Smoothed Particle Hydrodynamics Method: A Survey.

This paper presents a survey of Smoothed Particle Hydrodynamics (SPH) and its use in computational fluid dynamics. As a truly mesh-free particle method based upon the Lagrangian formulation, SPH has been applied to a variety of different areas in science, computer graphics and engineering. It has been established as a popular technique for fluid based simulations, and has been extended to successfully simulate various phenomena such as multi-phase flows, rigid and elastic solids, and fluid features such as air bubbles and foam. Various aspects of the method will be discussed: Similarities, advantages and disadvantages in comparison to Eulerian methods; Fundamentals of the SPH method; The use of SPH in fluid simulation; The current trends in SPH. The paper ends with some concluding remarks about the use of SPH in fluid simulations, including some of the more apparent problems, and a discussion on prospects for future work