Evaluatoin of Incompressible and Compressible SPH Methods in Modeling Dam Break Flows

Smoothed Particle Hydrodynamic (SPH) is an attractive Lagrangian tool for simulating flows with large displacement at free surface boundary. Two widely used subcategories of this method are Weakly compressible SPH (WCSPH) and truly Incompressible SPH (ISPH) methods. Each method has its individual advantages while there is not yet a global agreement about the preference of one method to another one. In this study, accuracy, stability and efficiency of these methods are compared in simulating dam break flow as a well-known hydraulic problem. To decrease unrealistic particle fluctuation especially at free surface boundary, a practical solution is applied to both methods while keeping their total accuracy. In addition, different solid boundary treatments are studied and their effect on total accuracy and stability of SPH methods are investigated. Based on the results, both ISPH and WCSPH methods can model free surface profiles properly if a proper solid boundary treatment is utilized. Meanwhile, local surface fluctuations can be damped in both methods efficiently by means of the modified surface viscosity. By means of original versions, it is concluded that ISPH method is generally more stable and more accurate particularly in modeling pressure field than WCSPH method. In addition, it is shown that ISPH method is faster than WCSPH method in solving a dam break flow with equal number of particles. On the other hand, ISPH in its original version using the divergence-free velocity scheme suffers from density loss problem. Since a lot of modifications have been introduced till now to overcome defections of both methods, it is not fair to compare methods with different modifications and therefore, similar modifications are applied in this study. Meanwhile, it can be concluded that each method is growing and is going its own way through enhancement.