Restrictor, Bend

Properties: adiabatic, not isentropic, symmetric, inlet based restrictor

Figure 96: Geometry of a bend

The geometry of a bend is shown in Figure 96. There are three types: TYPE = RESTRICTOR BEND IDEL CIRC, TYPE = RESTRICTOR BEND IDEL RECT, both with loss coefficients according to [34] and TYPE = RESTRICTOR BEND MILLER with coefficients taken from [54]. In the first and last type the bend is described by the following constants (to be specified in that order on the line beneath the *FLUID SECTION, TYPE = RESTRICTOR BEND IDEL CIRC or TYPE = RESTRICTOR BEND MILLER card):

• cross section before the bend $A$.
• cross section after the bend $A$.
• hydraulic diameter $D_h=4 A/P$, where $P$ is the perimeter of the cross section.
• radius of the bend $R$.
• bend angle $\alpha$ ($^\circ$).
• oil mass flow in the restrictor (only if the OIL parameter is used to define the kind of oil in the *FLUID SECTION card)
• not used (internally: oil material number)

They apply to circular cross sections. For rectangular cross sections the constants are as follows (to be specified in that order on the line beneath the *FLUID SECTION, TYPE=RESTRICTOR BEND IDEL RECT card):

• cross section before the bend $A$.
• cross section after the bend $A$.
• hydraulic diameter $D_h=4 A/P$, where $P$ is the perimeter of the cross section.
• radius of the bend $R$.
• bend angle $\alpha$.
• height $a_0$.
• width $b_0$.
• oil mass flow in the restrictor (only if the OIL parameter is used to define the kind of oil in the *FLUID SECTION card)
• not used (internally: oil material number)

The loss coefficients are those published by Idelchik [34] and Miller [54].

By specifying the parameter LIQUID on the *FLUID SECTION card the loss is calculated for liquids. In the absence of this parameter, compressible losses are calculated.

Example files: restrictor, restrictor-oil.