A general description of how to think about computational fluid dynamics (CFD) is given in the article, Simulating Fluid Flow with Free Surfaces. This article introduces the idea of reducing a simulation region into small volume control elements for which algebraic equations are constructed to describe the conservation of mass, momentum and energy exchanges with neighboring elements. Additionally, a simple method is introduced for a means of describing the motion of free fluid interfaces within the region of control elements.
Also for beginners, the article, What you should know about CFD modeling when selecting a CFD software, contains brief summaries of a variety of issues that are important considerations for constructing numerical solutions to fluid dynamic problems. Many of these issues, such as meshing, geometry representation, implicit versus explicit numerical methods and relaxation/convergence parameters are explored in greater detail in the remaining articles in CFD-101.