Numerical simulation of Submarine non-rigid landslide by an explicit three-step incompressible smoothed particle hydrodynamics

Deformable landslide body is modeled as a rheological material when SPH methods are used for numerical simulations. To increase accuracy, Carreau-Yasuda rheological model is chosen in this study. The model overcomes the weakness of the power-law model in predicting viscosity at zero and infinite shear strain rates. Also, a fully explicit three-step algorithm is proposed to solve governing equations. In the first step, intermediate velocities are computed in the presence of body forces. In the second step , they are used to compute divergence of stress tensor and to find intermediate particle positions. In the third step, pressure gradient in the momentum equation is merged with the continuity equation, and final particle velocity is calculated at the end of the time step. The algorithm is used in combination with Carreau-Yasuda model to simulate submarine non-rigid landslide. Comparison with experimental data indicates good agreement between calculated and observed water surface elevations with very low L2 relative error norm(εL2) and RMSE values. They are up to 70% lower than those from previous studies when Cross and Bingham rheological models were used with ISPH and WCSPH models, respectively. Moreover, shape and advancement of the non-rigid body made of sand are well captured

Numerical simulation of non-rigid landslide into reservoir with erodible sediment bed using SPH method

Landslide phenomenon in accumulated erodible bed sediments in a reservoir is one of the issues in hydraulic and sedimentation sciences that has received little attention. We intend to model two-dimensional changes of the water surface in a reservoir and of an erodible bed caused by a non-rigid landslide using a particle-based meshless approach. In this study, a fully explicit three-step algorithm is used. In this method, approximate numerical solution to the equations of the fluid dynamics is obtained by replacing the fluid with a set of particles. The governing equations for water flow and sand mass movement are solved for each particle. The movement of each particle, which is in interaction with other particles, is tracked. Experiments of a dam break on a dry bed, and submarine rigid and non-rigid landslides have been used to validate the method. Results indicate that the model was successfully calibrated against the measured data. Moreover, good agreement with the measured data demonstrates high capabilities of this method in simulating free-surface flows and wave-related phenomena. After the model validation, changes of erodible bed in a reservoir due to a non-rigid landslide were modelled. In this study, non-rigid landslide masses and sediment materials were modelled by non-Newtonian Carreau-Yasuda fluid, which is the novelty in the analysis of this type of natural hazard. Two possible scenarios were analyzed—one with the sliding material lighter, and the other with the sliding material heavier than the deposited sediments. The model was run until the landslide completely collapsed and its full impact was applied to the reservoir bed sediments. Additionally, we waited until the water level reached a steady state. These examples demonstrate that the model presented in this paper can be used as a reliable tool for modelling these phenomena

Nd:YAG laser hardening of AISI 410 stainless steel: microstructural evaluation, mechanical properties, and corrosion behavior

In this paper, a pulsed Nd:YAG laser with a maximum power of 700 W, was utilized to investigate the laser surface hardening of AISI 410 martensitic stainless steel. Focal point position, scanning speed and pulse width were considered as process variable parameters. Corrosion behavior of laser surface hardened samples were investigated by IVIUMSTAT apparatus in a 3.5wt% NaCl solution. Maximum microhardness, depth, and width of hardness and percentage of ferrite phase of metallographic and FESEM pictures were evaluated. Results show that surface hardness increased up to 762 HV. Results also reveal that the laser focal point position and pulse width are effective parameters in laser hardening process. In potentiodynamic polarization tests potential stated to increase at a rate of 1 mV/s from -0.4 V to 0.2 V. Results indicate that the corrosion resistance increased due to laser hardening process