ABSTRACT
The behavior of reactor coolants can be described by a set of conservation equations called the Navier–Stokes equations. These equations are a set of nonlinear partial differential equations based on Eulerian view of fluid mechanics, whose computational underpinnings were first espoused by Leonhard Euler around 1760. The flow of fluid through a reactor fuel assembly can be either natural or forced. When a fluid flows past a solid object such as a fuel rod or a pipe wall, the velocity of the fluid will be zero at the surface of the object and it will approach its free stream value when it moves further away from it. The behavior of the coolant around a nuclear fuel rod is determined primarily by how the velocity and pressure gradients behave in a thin layer of fluid close to the surface of the rod called the boundary layer.
