Pipe, Sudden Contraction

Figure 113: Sudden Contraction

A sudden contraction (Figure 113) is characterized by head losses $\Delta_1^2 F$ of the form:

$$\Delta_1^2 F = \zeta \frac{\dot{m}^2}{2 g \rho^2 A_2^2 },$$ (154)

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.