Initial and Boundary Conditions

Definition of initial and boundary conditions is part of the preprocessing step. To resolve the spatiotemporal variations of hydrodynamic variables such as pressure, velocity, and turbulence quantities within a modeled area, a solution of the governing equations of mass, momentum, and energy transport are required at the boundaries of the computational domain. These are special and problem-specific conditions commonly known as boundary conditions. Different types of boundary conditions can be implemented in a CFD model. In addition to the boundary conditions related to velocity and pressure, CFD models require definition of the turbulent quantities for the turbulence closure model. For civil and environmental engineering applications, cell zones can be utilized to model flow through porous media by adding a momentum sink term that creates a pressure drop that is proportional to the fluid velocity in a computational cell by introducing viscous and inertial resistance coefficients.