A sudden contraction (Figure 113) is characterized by head losses of the form:
where is a head loss coefficient depending on the ratio , is the mass flow, g is the gravity acceleration and is the liquid density. and are the larger and smaller cross section, respectively. Notice that this formula is only valid for . For a reverse mass flow, the formulas for a pipe enlargement have to be taken. Values for can be found in file “liquidpipe.f”.
The following constants have to be specified on the line beneath the *FLUID SECTION, TYPE=PIPE CONTRACTION card:
The gravity acceleration must be specified by a gravity type *DLOAD card defined for the elements at stake. The material characteristic can be defined by a *DENSITY card.
Example files: centheat1, pipe.