Ansys Fluent provides the ability to calculate streamwise-periodic — or “fully-developed” — fluid flow. These flows are encountered in a variety of applications, including flows in compact heat exchanger channels and flows across tube banks. In such flow configurations, the geometry varies in a repeating manner along the direction of the flow, leading to a periodic fully-developed flow regime in which the flow pattern repeats in successive cycles. Other examples of streamwise-periodic flows include fully-developed flow in pipes and ducts. These periodic conditions are achieved after a sufficient entrance length, which depends on the flow Reynolds number and geometric configuration.
Streamwise-periodic flow conditions exist when the flow pattern
repeats over some length 
, with a constant pressure drop across each repeating
module along the streamwise direction. Figure 1.1: Example of Periodic Flow in a 2D Heat Exchanger Geometry depicts one example of a
periodically repeating flow of this type that has been modeled by
including a single representative module.
