SPH fluids for viscous jet buckling

We present a novel meshfree technique for animating\ud free surface viscous liquids with jet buckling effects, such as\ud coiling and folding. Our technique is based on Smoothed Particle\ud Hydrodynamics (SPH) fluids and allows more realistic and\ud complex viscous behaviors than the preceding SPH frameworks\ud in computer animation literature. The viscous liquid is modeled\ud by a non-Newtonian fluid flow and the variable viscosity under\ud shear stress is achieved using a viscosity model known as Cross\ud model. The proposed technique is efficient and stable, and our\ud framework can animate scenarios with high resolution of SPH\ud particles in which the simulation speed is significantly accelerated\ud by using Computer Unified Device Architecture (CUDA)\ud computing platform. This work also includes several examples\ud that demonstrate the ability of our technique.FAPESP - processos nos. 2013/19760-5 e 2014/11981-5FAPES - processos no. 53600100/11CNP

SPH fluids for viscous jet buckling

We present a novel meshfree technique for animating\ud free surface viscous liquids with jet buckling effects, such as\ud coiling and folding. Our technique is based on Smoothed Particle\ud Hydrodynamics (SPH) fluids and allows more realistic and\ud complex viscous behaviors than the preceding SPH frameworks\ud in computer animation literature. The viscous liquid is modeled\ud by a non-Newtonian fluid flow and the variable viscosity under\ud shear stress is achieved using a viscosity model known as Cross\ud model. The proposed technique is efficient and stable, and our\ud framework can animate scenarios with high resolution of SPH\ud particles in which the simulation speed is significantly accelerated\ud by using Computer Unified Device Architecture (CUDA)\ud computing platform. This work also includes several examples\ud that demonstrate the ability of our technique.FAPESP - processos nos. 2013/19760-5 e 2014/11981-5FAPES - processos no. 53600100/11CNP

High Weissenberg number simulations with incompressible Smoothed Particle Hydrodynamics and the log-conformation formulation

Viscoelastic flows occur widely, and numerical simulations of them are important for a range of industrial applications. Simulations of viscoelastic flows are more challenging than their Newtonian counterparts due to the presence of exponential gradients in polymeric stress fields, which can lead to catastrophic instabilities if not carefully handled. A key development to overcome this issue is the log-conformation formulation, which has been applied to a range of numerical methods, but not previously applied to Smoothed Particle Hydrodynamics (SPH). Here we present a 2D incompressible SPH algorithm for viscoelastic flows which, for the first time, incorporates a log-conformation formulation with an elasto-viscous stress splitting (EVSS) technique. The resulting scheme enables simulations of flows at high Weissenberg numbers (accurate up to Wi=85 for Poiseuille flow). The method is robust, and able to handle both internal and free-surface flows, and a range of linear and non-linear constitutive models. Several test cases are considerd included flow past a periodic array of cylinders and jet buckling. This presents a significant step change in capabilties compared to previous SPH algorithms for viscoelastic flows, and has the potential to simulate a wide range of new and challenging applications.Comment: submitted to JNNFM Sept. 2020, revised March 202

Numerical solution of the Ericksen-Leslie model for liquid crystalline polymers free surface flows

In this paper we present a finite difference method on a staggered grid for solving two-dimensional free surface flows of liquid crystalline polymers governed by the Ericksen–Leslie dynamic equations. The numerical technique is based on a projection method and employs Cartesian coordinates. The technique solves the governing equations using primitive variables for velocity, pressure, extra-stress tensor and the director. These equations are nonlinear partial differential equations consisting of the mass conservation equation and the balance laws of linear and angular momentum. Code verification and convergence estimates are effected by solving a flow problem on 5 different meshes. Two free surface problems are tackled: A jet impinging on a flat surface and injection molding. In the first case the buckling phenomenon is examined and shown to be highly dependent on the elasticity of the fluid. In the second case, injection molding of two differently shaped containers is carried out and the director is shown to be strongly dependent on its orientation at the boundaries

Numerical simulation of drop impact and jet buckling problems using the eXtended Pom-Pom model

This work presents numerical simulations of two fluid flow problems involving moving free surfaces: the impacting drop and fluid jet buckling. The viscoelastic model used in these simulations is the eXtended Pom-Pom (XPP) model. To validate the code, numerical predictions of the drop impact problem for Newtonian and Oldroyd-B fluids are presented and compared with other methods. In particular, a benchmark on numerical simulations for a XPP drop impacting on a rigid plate is performed for a wide range of the relevant parameters. Finally, to provide an additional application of free surface flows of XPP fluids, the viscous jet buckling problem is simulated and discussed. (C) 2011 Elsevier B.V. All rights reserved.CNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnologico) [477858/2009-0, 305447/2010-6, 302631/2010-0, 471793/2010-8]Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)FAPESP (Fundacao de Amparo a pesquisa do Estado de Sao Paulo) [2009/15892-9]CAPESCAPES [BEX 2844/10-9]FCTFCTFEDER [PTDC/EME-MFE/114322/2009]FEDE

Bingham fluid simulations using a physically consistent particle method

The Bingham fluid simulation model was constructed and validated using a physically consistent particle method, i.e., the Moving Particle Hydrodynamics (MPH) method. When a discrete particle system satisfies the fundamental laws of physics, the method is asserted as physically consistent. Since Bingham fluids sometimes show solid-like behaviors, linear and angular momentum conservation is especially important. These features are naturally satisfied in the MPH method. To model the Bingham feature, the viscosity of the fluid was varied to express the stress-strain rate relation. Since the solid-like part, where the stress does not exceed the yield stress, was modeled with very large viscosity, the implicit velocity calculation was introduced so as to avoid the restriction of the time step width with respect to the diffusion number. As a result, the present model could express the stopping and solid-like behaviors, which are characteristics of Bingham fluids. The proposed method was verified and validated, and its capability was demonstrated through calculations of the two-dimensional Poiseuille flow of a Bingham plastic fluid and the three-dimensional dam-break flow of a Bingham pseudoplastic fluid by comparing those computed results to theory and experiment

Conformation constraints for efficient viscoelastic fluid simulation

The simulation of high viscoelasticity poses important computational challenges. One is the difficulty to robustly measure strain and its derivatives in a medium without permanent structure. Another is the high stiffness of the governing differential equations. Solutions that tackle these challenges exist, but they are computationally slow. We propose a constraint-based model of viscoelasticity that enables efficient simulation of highly viscous and viscoelastic phenomena. Our model reformulates, in a constraint-based fashion, a constitutive model of viscoelasticity for polymeric fluids, which defines simple governing equations for a conformation tensor. The model can represent a diverse palette of materials, spanning elastoplastic, highly viscous, and inviscid liquid behaviors. In addition, we have designed a constrained dynamics solver that extends the position-based dynamics method to handle efficiently both position-based and velocity-based constraints. We show results that range from interactive simulation of viscoelastic effects to large-scale simulation of high viscosity with competitive performance

Smoothed Particle Hydrodynamics-Based Viscous Deformable Object Modelling

Materials like fluids are long since important research objects of continuum mechanics as well as of computer graphics. Smoothed particle hydrodynamics(SPH) is one of the representation methods employed for continuous materials. Its simplicity in implementation and its realistic representation are drastically improved during the last decades. More recently, highly viscous fluids like honey, jam, and bread dough based on the SPH formulation have gained attention with impressive results. In this chapter, a novel implicit viscosity method is proposed. The internal viscosity forces are recursively calculated from the difference of the nearby velocities of the particles until they are small enough to be neglected. The proposed approach has longer time-steps compared with existing explicit viscosity methods, resulting in shorter computation time. Besides, the proposed method uses a physical viscosity coefficient, not an artificial one like in existing implicit viscosity methods, which helps predict the viscous behavior of continuous materials more accurately. The obtained results show that the computational time for the proposed approach is pre- dictable, while the accuracy in modelling the viscosity behaviour is similar or higher than existing methods

Accurate viscous free surfaces for buckling, coiling, and rotating liquids

© Christopher Batty & Robert Bridson | ACM 2008. This is the author's version of the work. It is posted here for your personal use. Not for redistribution. The definitive Version of Record was published in SCA '08: Proceedings of the 2008 ACM SIGGRAPH/Eurographics Symposium on Computer Animation, https://dl.acm.org/doi/10.5555/1632592.1632624?cid=81320487818.We present a fully implicit Eulerian technique for simulating free surface viscous liquids which eliminates artifacts in previous approaches, efficiently supports variable viscosity, and allows the simulation of more compelling viscous behaviour than previously achieved in graphics. Our method exploits a variational principle which automatically enforces the complex boundary condition on the shear stress at the free surface, while giving rise to a simple discretization with a symmetric positive definite linear system. We demonstrate examples of our technique capturing realistic buckling, folding and coiling behavior. In addition, we explain how to handle domains whose boundary comprises both ghost fluid Dirichlet and variational Neumann parts, allowing correct behaviour at free surfaces and solid walls for both our viscous solve and the variational pressure projection of Batty et al. [BBB07].This work was supported in part by a grant from the Natural Sciences and Engineering Research Council of Canada

A Physically Consistent Implicit Viscosity Solver for SPH Fluids

In this paper, we present a novel physically consistent implicit solver for the simulation of highly viscous fluids using the Smoothed Particle Hydrodynamics (SPH) formalism. Our method is the result of a theoretical and practical in‐depth analysis of the most recent implicit SPH solvers for viscous materials. Based on our findings, we developed a list of requirements that are vital to produce a realistic motion of a viscous fluid. These essential requirements include momentum conservation, a physically meaningful behavior under temporal and spatial refinement, the absence of ghost forces induced by spurious viscosities and the ability to reproduce complex physical effects that can be observed in nature. On the basis of several theoretical analyses, quantitative academic comparisons and complex visual experiments we show that none of the recent approaches is able to satisfy all requirements. In contrast, our proposed method meets all demands and therefore produces realistic animations in highly complex scenarios. We demonstrate that our solver outperforms former approaches in terms of physical accuracy and memory consumption while it is comparable in terms of computational performance. In addition to the implicit viscosity solver, we present a method to simulate melting objects. Therefore, we generalize the viscosity model to a spatially varying viscosity field and provide an SPH discretization of the heat equation