Sensitivity analysis of the initial distance between particles in the smoothed particle hydrodynamics method in simulation of dam break

  One of the general categories for discretization of equations and creation of computational geometry in the numerical methods is mesh-based and mesh-free methods. Previously, mesh-based methods have been a useful tool for flow modeling. However, these methods have some limitations for modeling of free surface flows, changeable boundaries and complicated geometry. In recent years, new generation of computational fluid dynamics methods named mesh-free methods has been introduced which one of them is smoothed particle hydrodynamics method. Smoothed particle hydrodynamics method is a fully Lagrangian method which solves the computational domain without using meshes. In this method, the integral expression is used for the approximation of functions, and smoothed functions have a key role in integral approximations. In the present study, the Incompressible Smoothed Particle Hydrodynamics method has been utilized for modeling of the dam break waves. In order to validation of the computational results, the reports of two experiments of dam break problem have been used. For the numerical modeling, the cubic spline function and initial distance between particles of 0.003 m, 0.004 m, 0.006 m & 0.008 m have been used, and the sensitivity analysis has been done on the effect of the initial distance between particles. Also, the effects of quantic spline smoothed function and beta smoothed function on results of modeling for two experimental data with the initial distance between particles of 0.006 m have been performed to reduce the computational costs. After reviewing the results of the modeling and comparison of the mean relative error related to each of smoothed functions were found that the most accurate results are related to the cubic spline smoothing function. In order to investigate the influence of the initial distance between particles in the modeling, a comparison was made between the results of the numerical model for various distances of 0.003 m, 0.004 m, 0.006 m, and 0.008 m for two experimental dam break tests for the superior cubic spline smoothed function. The results demonstrated that the ability of the numerical model has been enhanced by reducing the initial distance between the particles (increase the number of particles) in which applying the initial distance of 0.003 m would improve the results of the wave front by 43.5% and water level oscillation by 93.7% compared to the initial distance of 0.008 m. Keywords: Free-surface flows, Dam break, Numerical modeling, Incompressible Smoothed Particle Hydrodynamics method