O método ISPH (do inglês, Incompressible Smoothed Particle Hydrodynamics) é um método de aproximação livre de malha que, através de um conjunto finito de partículas e uma formulação completamente Lagrangeana, permite a solução de diversos tipos de escoamentos. Entretanto, sua aplicação para escoamentos bifásicos ainda é um desafio, principalmente no que refere-se à manutenabilidade da interface entre fluidos. Diante disso, nesta tese é apresentado o desenvolvimento de um código numérico baseado no método ISPH, sendo propostas duas técnicas de tratamento de interface. Para tanto é realizado um estudo a cerca do método, considerando diferentes metodologias, e analisando pontos específicos, tais como a solução do campo de pressões. São apresentados resultados que mostram a eficácia do método, tanto em escoamentos monofásicos, quanto em escoamentos multifásicos, onde, neste caso, são destacadas as melhorias obtidas através das técnicas de tratamento de interface propostas. Por fim, é realizado um estudo do comportamento de misturas bifásicas, com referência ao fenômeno da inversão de fase / Incompressible Smoothed Particle Hydrodynamics (ISPH) method is a meshless approximation that has been used to simulate several types of fluid flows, through a finite particle set and fully lagrangian formulation. The application of ISPH method in two-fluid flow simulations however, has presented many challenges, specially related to the presence of the interface between different fluids. Thus, we present in this study the development of a numerical code based on ISPH, introducing novel interface treatment techniques. A thorough study about this method is provided, considering different methodologies and analysing specific points such as the position of the interface and the obtained pressure field. Results have been presented to show the methods developed in this thesis efficiently simulate two-fluid flows, illustrating the improvements achieved by the proposed interface treatment techniques. Finally, a study of biphasic mixture behavior is carried out with reference to phase inversion phenomena

O método ISPH (do inglês, Incompressible Smoothed Particle Hydrodynamics) é um método de aproximação livre de malha que, através de um conjunto finito de partículas e uma formulação completamente Lagrangeana, permite a solução de diversos tipos de escoamentos. Entretanto, sua aplicação para escoamentos bifásicos ainda é um desafio, principalmente no que refere-se à manutenabilidade da interface entre fluidos. Diante disso, nesta tese é apresentado o desenvolvimento de um código numérico baseado no método ISPH, sendo propostas duas técnicas de tratamento de interface. Para tanto é realizado um estudo a cerca do método, considerando diferentes metodologias, e analisando pontos específicos, tais como a solução do campo de pressões. São apresentados resultados que mostram a eficácia do método, tanto em escoamentos monofásicos, quanto em escoamentos multifásicos, onde, neste caso, são destacadas as melhorias obtidas através das técnicas de tratamento de interface propostas. Por fim, é realizado um estudo do comportamento de misturas bifásicas, com referência ao fenômeno da inversão de fase / Incompressible Smoothed Particle Hydrodynamics (ISPH) method is a meshless approximation that has been used to simulate several types of fluid flows, through a finite particle set and fully lagrangian formulation. The application of ISPH method in two-fluid flow simulations however, has presented many challenges, specially related to the presence of the interface between different fluids. Thus, we present in this study the development of a numerical code based on ISPH, introducing novel interface treatment techniques. A thorough study about this method is provided, considering different methodologies and analysing specific points such as the position of the interface and the obtained pressure field. Results have been presented to show the methods developed in this thesis efficiently simulate two-fluid flows, illustrating the improvements achieved by the proposed interface treatment techniques. Finally, a study of biphasic mixture behavior is carried out with reference to phase inversion phenomena

Yes / This research paper presents an incompressible smoothed particle hydrodynamics (ISPH) technique to investigate a regular wave overtopping on the coastal structure of different types. The SPH method is a mesh-free particle modeling approach that can efficiently treat the large deformation of free surface. The incompressible SPH approach employs a true hydrodynamic formulation to solve the fluid pressure that has less pressure fluctuations. The generation of flow turbulence during the wave breaking and overtopping is modeled by a subparticle scale (SPS) turbulence model. Here the ISPH model is used to investigate the wave overtopping over a coastal structure with and without the porous material. The computations disclosed the features of flow velocity, turbulence, and pressure distributions for different structure types and indicated that the existence of a layer of porous material can effectively reduce the wave impact pressure and overtopping rate. The proposed numerical model is expected to provide a promising practical tool to investigate the complicated wave-structure interactions. / Nazarbayev University Seed Grant, entitled “Environmental assessment of sediment pollution impact on hydropower plants”. S. Shao also acknowledges the Royal Society Research Grant (2008/R2 RG080561)

Fluid structure interactions in the presence of a free surface includes complex phenomena, such as slamming, air entrainment, transient loads, complex free surface profiles and turbulence. Hence, an appropriate and efficient numerical method is required to deal with these type of problems (efficient both in problem setup and numerical solution). Eulerian mesh-based methods can be used to solve different types of problems, however they have difficulties in problems involving moving boundaries and discontinuities (e.g. fluid structure interactions in the presence of a free surface). Smoothed Particle Hydrodynamics (SPH) is a mesh-less Lagrangian particle method, ideal for solving problems with large deformation and fragmentation such as complex free surface flows. The SPH method was originally invented to study astrophysical applications and requires modifications in order to be applied for hydrodynamic applications. Applying solid boundary conditions for hydrodynamic applications in SPH is a key difference to the original SPH developed for astrophysics. There are several methods available in literature to apply solid boundaries in SPH. In this research, an accurate solid boundary condition is used to calculate the pressure at the boundary particles based on the surrounding fluid particles. The two main methods to calculate the pressure in the SPH method are the weakly compressible SPH (WCSPH) and the incompressible SPH (ISPH) approaches. The WCSPH uses the equation of state while ISPH solves Poisson's equation to determine the pressure. In this dissertation, an explicit incompressible SPH (ISPH) method is used to study nonlinear free surface applications. In the explicit ISPH method, Poisson's equation is explicitly solved to calculate the pressure within a projection based algorithm. This method does not require solving a set of algebraic equations for pressure at each time step unlike the implicit method. Here, an accurate boundary condition along with an accurate source term for Poisson's equation is used within the explicit method. Also, the sub-particle turbulent calculation is applied to the explicit ISPH method (which handles large-scale turbulent structures implicitly) in order to calculate the flow field quantities and consequently forces on the device more accurately. The SPH method is typically computationally more expensive than Eulerian-based CFD methods. Therefore, parallelization methods are required to improve the performance of the method, especially for 3D simulations. In this dissertation, two novel parallel schemes are developed based on Open Multi Processing (OpenMP) and Message Passing Interface (MPI) standards. The explicit ISPH approach is an advantage for parallel computing but our proposed method could also be applied to the WCSPH or implicit ISPH. The proposed SPH model is used to simulate and analyze several nonlinear free surface problems. First, the proposed explicit ISPH method is used to simulate a transient wave overtopping on a horizontal deck. Second, a wave impacting on a scaled oscillating wave surge converter (OWSC) is simulated and studied. Third, the performance and accuracy of the code is tested for a dam-break impacting on tall and short structures. Forth, the hydrodynamic loads from the spar of a scaled self-reacting point absorber wave energy converter (WEC) design is studied. Finally, a comprehensive set of landslide generated waves are modeled and analyzed and a new technique is proposed to calculate the motion of a slide on an inclined ramp implicitly without using a prescribed motion. / Graduate

No / The standard shallow water equations (SWEs) model is often considered to provide weak solutions to the dam-break flows due to its depth-averaged shock-capturing scheme assumptions. In this study, an improved SWEs model using a recently proposed Surface Gradient Upwind Method (SGUM) is used to compute dam-break flows in the presence of a triangular hump. The SGUM allows the SWEs model to stably and accurately reproduce the highly complex shock currents caused by the dam-break event, as it improves the treatment of SWEs numerical source terms, which is particularly crucial for simulating the wet/dry front interface of the dam-break flow. Besides, an Incompressible Smoothed Particle Hydrodynamics (ISPH) modeling technique is also employed in this study to compare with the performance of the SGUM-SWEs model. The SPH method is totally mesh free and thus it can efficiently track the large free surface deformation. The ISPH approach uses a strictly incompressible two-step semi-implicit solution method. By reproducing a documented experimental dam-break flow, it has demonstrated that both model simulation results gave good agreement with the experimental data at different measurement locations. However, the ISPH simulations showed a better prediction of the dam-break peak wave building-up time, where its superiority was demonstrated. Furthermore, the ISPH model could also predict more detailed flow surface profiles across the streamwise flow direction and the velocity and pressure structures.