Waterjet-guided material processing is a technique that combines the capabilities of laser material processing with water jetting. In this study, we have investigated laser beam propagation in a waterjet column by numerically solving the Maxwell equations and the heat equation. A 1064 nm laser and its frequency-doubled 532 nm laser were chosen for the simulations, and the finite-difference time-domain (FDTD) method was employed for solving the Maxwell equations. The coupling effect of the laser and waterjet was simulated with different numerical apertures and different waterjet column diameters. Extensive investigations on laser absorption phenomena regarding the outer surface geometries of the waterjet (cylindrical shape with and without sinusoidal perturbation), and temperature distributions were also conducted. To the best of the authors’ knowledge, this is the first electrodynamic simulation of laser beam propagation and interaction with a water column in waterjet-guided laser processing. Some interesting findings concerning laser beam absorption characteristics inside a waterjet column were revealed.
This article presents a novel monolithic numerical method for computing flow-induced stresses for problems involving arbitrarily-shaped stationary boundaries. A unified momentum equation for a continuum consisting of both fluids and solids is derived in terms of velocity by hybridizing the momentum equations of incompressible fluids and linear elastic solids. Discontinuities at the interface are smeared over a finite thickness around the interface using the signed distance function, and the resulting momentum equation implicitly takes care of the interfacial conditions without using a body-fitted grid. A finite volume approach is employed to discretize the obtained governing equations on a Cartesian grid. For validation purposes, this method has been applied to three examples, lid-driven cavity flow in a square cavity, lid-driven cavity flow in a circular cavity, and flow over a cylinder, where velocity and stress fields are simultaneously obtained for both fluids and structures. The simulation results agree well with the results found in the literature and the results obtained by COMSOL Multiphysics®.
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