Baroclinic Turbulence with Varying Density and Temperature

Doyub Kim, Seung Woo Lee, Oh-young Song, Hyeong-Seok Ko

The explosive or volcanic scenes in motion pictures involve complex turbulent flow as its temperature and density vary in space. To simulate this turbulent flow of an inhomogeneous fluid, we propose a simple and efficient framework. Instead of explicitly computing the complex motion of this fluid dynamical instability, we first approximate the average motion of the fluid. Then, the high-resolution dynamics is computed using our new extended version of the vortex particle method with baroclinity. This baroclinity term makes turbulent effects by generating new vortex particles according to temperature/density distributions. Using our method, we efficiently simulated a complex scene with varying density and temperature.

Baroclinic Turbulence with Varying Density and Temperature

Procedural Fluid Modeling of Explosion Phenomena Based on Physical Properties

Genichi Kawada, Takashi Kanai

We propose a method to procedurally model the fluid flows of explosion phenomena by taking physical properties into account. Explosion flows are always quite difficult to control, because they easily disturb each other and change rapidly. With this method, the target flows are described by control paths, and the propagation flows are controlled by following these paths. We consider the physical properties, which are the propagations of the pressure generated by the ignition, the detonation state caused by the pressure and the fuel combustions. Velocity, density, temperature and pressure fields are generated procedurally, and the fluid flows are computed from these four fields based on grid-based fluid simulations. Using this method, we can achieve a fluid motion that closely resembles one generated solely through simulation. This method realizes the modeling of flows controlled frame by frame and follows the flow’s physical properties.

Procedural Fluid Modeling of Explosion Phenomena Based on Physical Properties

Graph-based Fire Synthesis

Yubo Zhang, Carlos Correa, Kwan-Liu Ma

We present a novel graph-based data-driven technique for cost-effective fire modeling. This technique allows composing long animation sequences using a small number of short simulations. While traditional techniques such as motion graphs and motion blending work well for character motion synthesis, they cannot be trivially applied to fluids to produce results with physically consistent properties which are crucial to the visual appearance of fluids. Motivated by the motion graph technique used in character animations, we introduce a new type of graph which can be applied to create various fire phenomena. Each graph node consists of a group of compact spatialtemporal flow pathlines instead of a set of volumetric state fields. Consequently, achieving smooth transitions between discontinuous graph nodes for modeling turbulent fires becomes feasible and computationally efficient.The synthesized particle flow results allow direct particle controls which is much more flexible than a full volumetric representation of the simulation output. The accompanying video shows the versatility and potential power of this new technique for synthesizing realtime complex fire at the quality comparable to production animations.

Graph-based Fire Synthesis

Animation of Chemically Reactive Fluids using a Hybrid Simulation Method

Chemical phenomena abound in the real world, and often comprise indispensable elements of visual effects that are routinely created in the film industry. In this paper, we present a hybrid technique for simulating chemically reactive fluids, based on the theory of chemical kinetics. Our method makes synergistic use of both Eulerian grid-based methods and Lagrangian particle methods to simulate real and hypothetical chemical mechanisms effectively and efficiently. We demonstrate that by modeling chemical reactions using a particle system, an established, physically based fluid system can be extended easily to generate a wide range of chemical phenomena, ranging from catalysis and erosion to fire and explosions, with only a small additional cost.

Animation of Chemically Reactive Fluids Using a Hybrid Simulation Method

Wrinkled Flames and Cellular Patterns

“We model flames and fire using the Navier-Stokes equations combined with the level set method and jump conditions to model the reaction front. Previous works modeled the flame using a combination of propagation in the normal direction and a curvature term which leads to a level set equation that is parabolic in nature and thus overly dissipative and smooth. Asymptotic theory shows that one can obtain more interesting velocities and fully hyperbolic (as opposed to parabolic) equations for the level set evolution. In particular, researchers in the field of detonation shock dynamics (DSD)
have derived a set of equations which exhibit characteristic cellular patterns. We show how to make use of the DSD framework in the context of computer graphics simulations of flames and fire to obtain interesting features such as flame wrinkling and cellular patterns.”

Wrinkled Flames and Cellular Patterns