This chapter provides detail on how to use appropriate boundary conditions in CFX for basic models. Information on the mathematical representation of CFX boundary conditions is available in Boundary Conditions in the CFX-Solver Theory Guide. Extended information for more complex models is provided in the related modeling chapters. For example, for information on multiphase outlets, you should consult the multiphase modeling section for specific advice. For details, see Boundary Conditions in Multiphase Flow.

The equations relating to fluid flow can be closed (numerically) by the specification of conditions on the external boundaries of a domain. It is the boundary conditions that produce different solutions for a given geometry and set of physical models. Hence, boundary conditions determine to a large extent the characteristics of the solution you obtain. Therefore, it is important to set boundary conditions that accurately reflect the real situation to enable you to obtain accurate results.