Pipe, Sudden Contraction

**Figure:** Sudden Contraction
$\begin{figure}\epsfig{file=Contraction.eps,width=8cm}\end{figure}$

A sudden contraction (Figure ) is characterized by head losses \Delta_1^2 F of the form:

\Delta_1^2 F = \zeta \frac{\dot{m}^2}{2 g \rho^2 A_2^2 },

(155)

where \zeta is a head loss coefficient depending on the ratio A_2/A_1, \dot{m} is the mass flow, g is the gravity acceleration and \rho is the liquid density. A_1 and A_2 are the larger and smaller cross section, respectively. Notice that this formula is only valid for \dot{m} \ge 0. For a reverse mass flow, the formulas for a pipe enlargement have to be taken. Values for \zeta 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:

A_1
A_2 \;\;\;(\le A_1)

The gravity acceleration must be specified by a gravity type *DLOAD card defined for the elements at stake. The material characteristic \rho can be defined by a *DENSITY card.

Example files: centheat1, pipe.