The Simulation Research Of Large Amount Of Data Liquid-solid Coupling Based On The SPH

With the rapid development of multimedia technology, people today gradually require more from digital vision, especially in the aspect of natural landscape visual simulation. People pay more and more attention to the visual simulation of the natural disaster phenomenon etc., and require much more reality and the reliability. To reach the request towards visual effects simulation of natural disaster such as debris flow, researchers have done research for many years about fluid simulation in the domain of virtual reality and graphics. They have made many progresses, but still not made much progress in fluid solid coupling of debris flow visual simulation. On the other hand, in the field of fluid mechanics, researches have done consistent research about the numerical simulation of fluid solid coupling, and have made some great achievement. It’s a big challenge to solve the problem of great data quantity fluid solid coupling simulation like debris flow visual simulation. While using the method and theory of fluid mechanics numerical simulation, both physical reality and visual deceive of visual simulation should be considered.This article is under the support of Gansu Province Department of land and resources project "Zhouqu devastating Mountain torrents debris flow disaster origin and preventing and controlling plan virtual demonstration"(No.2010175033), and takes Zhouqu debris flow visual effects simulation as an example and does research on great data quantity fluid solid coupling simulation. Based on the physical fluid visual effects simulation, it states the realization process and principle of the fluid visual effects. Visual effect is the visual images produced by active sequence frame continuous reflection when creating, changing or enhancing any actual images. In the domain of virtual reality and graphics, the visual simulation of the fluid has two key points:the first is the accurate simulation of the movement shape, and the second is the accurate simulation of the material quality texture. Because of the limitation of objective image understanding research, it can only be evaluated subjectively. This article has carried on the exploration into the evaluation method, proposing the evaluation factor and weight coefficient of fluid visual simulation. With full understanding of fluid dynamics Navier-Stokes equation and the situation of debris flow visual effects simulation, it develops the SPH method derived from Lagrange method and proposes one kind of new method suitable for great data quantity fluid solid coupling simulation, realize the fluid solid coupling simulation combining with a new method of fixed-point rotation of rigid body, and at last powerfully solves the problems that debris flow visual effects simulation faces.This article takes debris flow visual effects simulation as an example and launches the research from two aspects towards the great data quantity fluid solid coupling simulation:on the one hand, based on Navier-Stokes equation in fluid mechanics, it does research in a SPH way to investigate the great data quantity fluid solid coupling simulation in order to solve the bottleneck problem of parallel motion computing efficiency of the fluid part and rigid body part and accelerate the speed of visual effects simulation, reducing the complexity of visual simulation calculation; on the other hand, based on the classical rigid body rotation theory, it does research towards the rotation simulation of the actual rigid body in debris flow, with the purpose of enhancing the rotation computational accuracy of the rigid body and the validity of the visual effects. The related work of this article can be induced into the following several points:1. An evaluation method of fluid simulation is put forward. The focal point of this method is the evaluation of photorealistic. The visual image must accord with the real-world perspective relation, the dynamic functions, the lighting attributes, and the texture, etc. Following this principle, the evaluation system of visual fluid simulation is set up, the comprehensive evaluation method is designed, and the evaluation index and weight coefficients are determined.2. SPH is a non-grid method based on the Lagrangian method, expressing fluid made up by the particles (parcel). The physic attributes of a particle are calculated by the interpolations of other particles’attributes in the smooth length of it. The simulation of debris flow is a large dataset fluid-solid coupling, it’s important to simulate the movement of large amounts of rigid in the fluid. It must be considered as the coupling of two kinds of movement:the movement of the fluid and the movement of the rigid, which include interactions not only between the rigid and the fluid but also between the rigid. It is an extremely complicate nonlinear problem if completely based on physic. It brings about large amount of computation and is hard to get an accurate result. This paper gives an improved SPH method based on the characters of the Lagrangian method. For the large dataset actual rigid, they are abstracted into the rigid particles. By the interaction between the rigid and fluid particles, the movement of the rigid is calculated accurately, so it lowers the complexity of the calculation. Meanwhile, this paper brings the vortex force and impact that the fluid particles are affected by in SPH method, improving the reality of the fluid motion in the debris visual simulation.3. In the method this paper gives, the translation of the rigid particles acting for the actual rigid is calculated, then it comes to simulate the rotation of the actual rigid in order to get more realistic visual effect. The rotation of the actual rigid in debris flow can be thought as a fixed-point rotation based on classical theory of rotation. But it’s sufficiently complex to calculate the rotation by the crashes between the rigid and other objects completely following the classical rigid movement theory. Since that, this paper gives a method of calculating the rotation of the actual rigid by force domain. All the fluid particles in the force domain of an actual rigid will act on the rotation of the rigid. The rotation of the actual rigid is determined by the force ball, which develop the realistic of the rigid body motion in the visual simulation of debris flow.4. Taking the visual effect simulation of Zhouqu debris flow as an example, this paper forms a simulation framework of the debris flow visual effect. Based on the specific analysis of the Zhouqu debris flow, the paper puts forward a modeling method used for the rigid body part and fluid part in the debris flow, meanwhile,it gives a detailed description about the surface reconstruction principle with SPH method applying in the fluid research. For debris flow interacting with the surrounding environment, the crash between debris flow and the topographic map made up by height field is calculated in a simplified algorithm by searching the location of the particles, and the crash between debris flow and the buildings in Sweep and Prune algorithm and boundary virtual particles method. For the breaking down simulation of the buildings, a method of Voroni map is used to design the simulation of debris flow washing off the buildings. Besides, the material texture and lighting of the rigid body part and fluid part in the debris flow are analyzed, as well as the implementation. Finally, the whole visual effect simulation of the Zhouqu debris flow is evaluated in the method that this paper puts forward.