Improving Boundary Condition in Wave Run-up Simulation using SPH-GPU

Wave run up and overtopping are two important processes in design of coastal structures and in definition of their crest elevation. Wave run up in contribution with wave breaking generates local turbulences as well as large deformations around free surface profile. Smoothed Particle Hydrodynamic (SPH) method as a powerful Lagrangian method in modeling free surface flows is modified and applied in this study to estimate wave run up properly. Two modifications i.e. stepped and smoothed approaches are introduced to implement bed shear stress in SPH models. The results are compared with reliable predictions based on experimental and analytical studies. It is concluded that neglecting bed shear stress as a common practice in SPH methods can generate significant errors in estimating wave run up, while these errors are diminished efficiently by means of the introduced methods. The rate of this improvement, however, depends on slope geometry as well as wave condition and it is more sensible in simulating sliding waves over the bed slope during run up phenomenon. In this case, 90% error of the unmodified methods has been decreased to 6% using the modified SPH method. In addition, parallel processing using graphical processing units (GPU) are utilized to increase the efficiency of the modified model. The efficiency of GPU in comparison with CPU is evaluated and computational costs of different numerical steps are analyzed. It is observed that calculation of forces is the main time consuming step and using GPU can speed up the modified model significantly.