Simulating incompressible flow using Particle-based techniques have been gaining interest of researchers for more than a decade. Smoothed Particle Hydrodynamics (SPH) is a common technique for simulating fluids solely using pairwise forces between particles. SPH has important potential benefits, such as the ability to handle complex boundaries and small-scale phenomena. This dissertation explains some techniques that employ those potential benefits of SPH.
The dissertation starts by reviewing the basic SPH technique and the recent advances in SPH. Secondly, a versatile technique for handling boundaries with two-way rigid-fluid coupling is explained. The technique has several important properties, such as; support for arbitrary rigid objects with large density ratios, support for thin shells including non-manifold geometries, momentum conservation, ability to handle multiphase flow, and allowing large time-steps. Furthermore, the technique addresses particle deficiency related issues of SPH near solid boundaries, which prevents spatial and temporal discontinuities of the physical properties of the fluid. Those benefits are illustrated through a variety of simulation scenarios. Afterwards, in the next chapter, the rigid-fluid coupling technique is extended to support elastic solids with arbitrarily large expansions in SPH, while retaining all of its useful properties. It is shown that this extension produces stable and realistic interactions of SPH fluids with both slowly and rapidly deforming solids.
The next contribution explained in the thesis addresses both fluid-air and fluid-solid interfaces in SPH for more realistic fluid behavior by employing a new surface tension force and a new adhesion force. The surface tension force can handle large surface tensions in a realistic way, which lets it handle challenging real scenarios, such as: water crown formation, various types of fluid-solid interactions, and even droplet simulations. Furthermore, it prevents particle clustering at the fluid-air interface where inter-particle pressure forces are incorrect. Our adhesion force allows plausible two-way attraction of fluids and solids and can be used to model different wetting conditions. It is also shown that the combination of two forces allows simulating a variety of interesting effects in a plausible way.
Lastly, the thesis focuses on the efficient simulation and visualization of fluid-air mixtures, namely, foam to enhance detail. For the foam simulation, physically motivated rules are employed to generate, advect and dissipate foam on an existing SPH simulation as a post processing step. The main contribution explained in detail in that part is a technique for the efficient rendering of large-scale foam data in screen space using a GPU based rendering pipeline. The explained approach employs a multi-pass rendering technique to imitate some of the effects that are commonly accomplished by using expensive ray-tracing based methods. It is demonstrated through different scenarios that the presented pipeline is able to produce convincing foam renderings for large-scale scenarios.
Journal of Coastal Engineering and Marine Energy, Special Issue on Particle Methods (June 2016)