This book presents results from applying Reflective Boundary Conditions (RBC) in particle simulations coupled with the Smoothed Particle Hydrodynamics (SPH) Method in two- and three-dimensional domains. The contribution of this work lies in the presentation of the state of the art regarding the application of physical and realistic boundary conditions in the continuum domain, which is an advance in the artificial computational boundary treatment carried out in most SPH simulations. By reading this work, researchers from different fields dealing with Computational Fluid Dynamics (CFD) will be aware of the most recent results of applying the SPH method coupled with RBC, confirming its scientific validity and encouraging its implementation in other problems. This multidisciplinary work is aimed at undergraduate and postgraduate students, researchers, software developers, and other engineering, physics, chemistry, mathematics, and related sciences professionals. In addition, this book: Presents the fundamentals of the reflective boundary conditions and justifies their utilisation in the continuum domain Presents the validation tests for the reflective boundary treatment technique Presents the state-of-the-art of the application of the reflective boundary conditions in two- and three- dimensions.