Yalan Zhang

Efficient extracting surfaces approach employing anisotropic kernels for SPH fluids

AbstractParticles 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

Adaptively stepped SPH for fluid animation based on asynchronous time integration

Abstract 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.

A Symmetry Particle Method towards Implicit Non‐Newtonian Fluids

In this paper, a symmetry particle method, the smoothed particle hydrodynamics (SPH) method, is extended to deal with non‐Newtonian fluids. First, the viscous liquid is modeled by a non‐Newtonian fluid flow and the variable viscosity under shear stress is determined by the Carreau‐Yasuda model. Then a pressure correction method is proposed, by correcting density error with individual stiffness parameters for each particle, to ensure the incompressibility of fluid. Finally, an implicit method is used to improve efficiency and stability. It is found that the nonNewtonian behavior can be well displayed in all cases, and the proposed SPH algorithm is stable and efficient.

Surface Tension Model Based on Implicit Incompressible Smoothed Particle Hydrodynamics for Fluid Simulation

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.

Adaptiving Time Steps for SPH Cloth-Fluid Coupling

We propose a new cloth-fluid coupling scheme which takes the advantages of the position-based method. With the constraint to distance and angle, deformable sheet could be implemented and coupled with fluid particles. Furthermore, an adaptive time-stepping method is adopted for the cloth-fluid coupling, which increases and decreases the required time step automatically according to the scenario. While comparatively large time steps can be used, the efficiency of the simulation is significantly improved compared to the constant time-stepping.

A Density-Correction Method for Particle-Based Non-Newtonian Fluid

We propose a novel non-Newtonian fluid simulation method for SPH. The variable viscosity under shear stress is achieved using a viscosity model known as Cross model. By adopting a density-correction scheme, larger time step is available for simulation. The achieved results show that both Newtonian fluid and non-Newtonian fluid could be achieved by our model. Furthermore, density-correction scheme improves the stability and efficiency of simulation significantly.

Anisotropic Surface Reconstruction for Multiphase Fluids

Under particle-based framework, level set is generally defined for fluid surfaces and is integrated with marching cubes algorithm to extract fluid surfaces. In these methods, anisotropic kernels method has proven successful for reconstructing fluid surfaces with high quality. It can perfectly represent smooth surfaces, thin stream and sharp features of fluids compare to other methods. In this paper, we propose a novel approach to extend it to the simulation of multiphase fluids simulation. In order to ensure fine effects for both fluid surface and multiphase interface, we modify the calculation of original anisotropic kernels and address a binary tree strategy for reconstruction. Our method can extract fluid surfaces simply and effectively for particle-based multiphase simulation. It solved the problem of overlaps and gaps at multiphase interface that exist in traditional methods. The experimental results demonstrate that our method keep a good fluid surface and interface effects.

An Improved Anisotropic Kernels Surface Reconstruction Method for Multiphase Fluid

This paper improves the anisotropic kernels surface reconstruction method and apples it to multiphase immiscible fluid surface reconstruction. An unexpected phenomenon appears when using the anisotropic kernels surface reconstruction directly (e.g. the gap and overlap at the interface of multiphase fluid surface). We eliminate the gap by considering the neighbor particles of other phase fluid in the kernels function and eliminate the overlap by signed color field in the marching cube process. The improved method will be able to reconstruct a common surface at the interface of the multiphase fluid.

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.

The Non-Newtonian Fluid Simulation Based on Predictive-Corrective Incompressible SPH

A novel non-Newtonian fluid simulation method for SPH is proposed in this article. The viscous liquid is modeled by a non-Newtonian fluid flow, and the variable viscosity under shear stress is achieved using a viscosity model known as Cross model. To avoid tensile instability and improve numerical stability, a predictive-corrective method, aimed at correcting density error, of setting up individual stiffness parameters for each particle to be added. Furthermore, to improve the overall efficiency of the proposed method, a global adaptive time-stepping method that adjust the time step automatically in accordance with individual scenarios is utilized.