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Title: Improved incompressible SPH method for predicting wave impacts on coastal structures
Author: Gui, Qinqin
ISNI:       0000 0004 5359 085X
Awarding Body: University of Dundee
Current Institution: University of Dundee
Date of Award: 2014
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Smoothed Particle Hydrodynamics (SPH) is a simple and attractive meshless Lagrangian particle method for simulating free surface flows and has been widely applied in predicting wave impacts on coastal structures. However, despite the superior theoretical basis the performance of the existing Incompressible SPH models based on either a density invariant or a velocity divergence-free formulation is often not better than the recently improved Weakly Compressible SPH models. This could be largely caused by the particular formulations of the Pressure Poisson Equation (PPE) source term in the existing ISPH models and a better formulation of this source term can be expected to significantly improve the accuracy of the ISPH models This thesis presents an improved incompressible smoothed particle hydrodynamics (ISPH) method for wave impact applications by combining the density invariant and velocity divergence free formulations in a weighted average manner to form a general source term. The model is then applied to two problems: (1) dam-breaking wave impact on a vertical wall and (2) solitary wave run-up and impact on a coastal structure. The computational results have indicated that the new source term treatment can predict the wave impact pressure and force more accurately compared with using either density invariant or a velocity divergence-free formulation alone. It was further found that depending on the application case, the influence of the density invariant and velocity divergence-free parts could be quite different. A simple parameterisation that relates the weighting coefficient a in the mixed pressure source term to the ratio of the characteristic height to length scales of the flow system is proposed and evaluated. In order to gain further insight into the effects of the source term formulations on the impact pressure prediction, three more benchmark fluid impact problems including two dam break flows and one solitary wave impact are investigated using the three different ISPH numerical schemes, respectively. The computational results are validated against either the experimental data or numerical data based on the WCSPH. The in-depth numerical analysis has revealed that the pure density-invariant formulation can lead to relatively large divergence errors while the velocity divergence-free formulation may cause relatively large density errors. As compared with these two approaches the mixed source term formulation performs much better having the minimum total errors in all test cases. Finally, the SPH model was applied to study the wave interaction with porous structure to investigate the flow motion in and around the porous structure. In order to describe correctly the flow through the interface between the porous region and pure fluid region within the SPH framework a heuristic and boundary treatment method was proposed. The SPH model was validated against the theoretical data of wave propagating over a porous bed and further investigated by comparing the predicted wave surface profile and velocity results with the experiment data for a typical case of flow motion inside of a submerged the porous structure. A good agreement is obtained between the numerical results and experiment data. All these demonstrate that the improved ISPH model developed in this work is capable of modelling the wave interaction with porous structure.
Supervisor: Dong, Ping Sponsor: China Scholarship Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available