
Many problems permit the entire computational domain to be referred to as a single rotating reference frame (hence the name SRF modeling). In such cases, the equations given in Section 10.2.2 are solved in all fluid cell zones. Steadystate solutions are possible in SRF models provided suitable boundary conditions are prescribed. In particular, wall boundaries must adhere to the following requirements:
Rotationally periodic boundaries may also be used, but the surface must be periodic about the axis of rotation. As an example, it is very common to model flow through a blade row on a turbomachine by assuming the flow to be rotationally periodic and using a periodic domain about a single blade. This permits good resolution of the flow around the blade without the expense of model all blades in the blade row (see Figure 10.2.2).
Flow boundary conditions in FLUENT (inlets and outlets) can, in most cases, be prescribed in either the stationary or rotating frames. For example, for a velocity inlet, one can specify either the relative velocity or absolute velocity, depending on which is more convenient. In some cases (e.g. pressure inlets) there are restrictions based upon the velocity formulation which has been chosen. For additional information on these and other boundary conditions, see Section 10.7 and Chapter 7.