Consider a sudden expansion placed in a duct (Fig.3.33).
The flow does not follow the area changes as suddenly as the
geometry does. Any flow will find the sudden area increase
difficult to negotiate. In fact a recirculating flow develops as
was seen in case of the orifice flow. This gives to losses which
are reflected in the total pressure at downstream being reduced.
It is possible to calculate this loss from a control volume
(c) Aerospace, Mechanical & Mechatronic Engg. 2005
University of Sydney