Properties: adiabatic, not isentropic, directional, inlet based restrictor if A_1 < A_2 and outlet based restrictor if A_2 < A_1.

A user-defined restrictor is described by the following constants (to be specified in that order on the line beneath the *FLUID SECTION, TYPE=RESTRICTOR USER card):

- upstream cross section A_1.
- downstream cross section A_2.
- hydraulic diameter D_h defined by D_h=4 A/P where A is the area of the smallest cross section and P is the perimeter of the smallest cross section.
- loss coefficient \zeta.
- 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)

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.