This link models fixed-area thin orifice devices such as restriction plates, orfice plates, venturi tubes, etc. It is similar to the generic GunnsFluidConductor link, but with these main differences:

• It implements higher-fidelity flow equations for choked and non-choked gas flows,
• It implements turbulent and laminar flow for gas & liquids,
• It is configured with actual hardware parameters such as diameter and flow coefficient, as opposed to the generic GUNNS conductivity.

Liquid flows still use the same Bernoulli equation as GunnsFluidConductor.

The link can optionally model the istentropic cooling of a gas as it expands across the pressure drop, and the amount of this effect can be tuned. This link does not model any other thermal effects and no other changes to the fluid passing through it are done. This link does not model forced heat convection with the walls.

This link can be connected to nodes in the same ways as the GunnsFluidConductor.

Port Connection Rules (These are limitations on the port connection to nodes that the link enforces in run-time):

• Ports 0 and 1 cannot connect to the same non-Ground node.

Other Rules (These are extra rules you should always try to follow):

• Same as GunnsFluidConductor.

Configuration Data Parameters:

• coefficientType (default = GunnsFluidHiFiOrificeConfigData::DISCHARGE_COEFF): There are several definitions of the "flow coefficient" of an orifice, and this term selects the one you want to use. This determines how the link interprets the coefficientValue term below. This allows you to use the type of value that may be quoted in the vendor documentation for the orifice you are modeling, for convenience. The options are:


• GunnsFluidHiFiOrificeConfigData::DISCHARGE_COEFF: This is the Coefficient of Discharge, also denoted as C_d. When this option is used, the value must be > 0 and <= 1, and it is dimensionless. In lieu of vendor documentation, you may be able to derive a suitable C_d value from theory and other orifice geometry parameters. There is a discussion of this theory here.


• GunnsFluidHiFiOrificeConfigData::FLOW_FACTOR: This is the Flow Factor, also denoted as K_v. When this option is used, the value is in units of (m3/h) and must be > 0 and <= (53447 * throatDiameter²).


• GunnsFluidHiFiOrificeConfigData::FLOW_COEFF: This is the Flow Coefficient, also denoted as C_v. This is basically the Imperial units equivalent of K_v. When this option is used, the value is in units of US gallons/minute and must be > 0 and <= (46232 * throatDiameter²).


• coefficientValue (default = 0.0, must be > 0 and max value depends on the coefficientType, described above): This is the value of the coefficient of the type specified by coefficientType. Higher values will make the orifice flow a higher flow rate at a given pressure across it.


• throatDiameter (default = 0.0 (m2), must be > 0): This is the width of the orifice passage at its narrowest point. This is typically given in the vendor documentation for the device.


• criticalReynolds (default = 0.0, must be >= 0): This is an optional term to define the Reynolds number at which the orifice transitions between turbulent and laminar flow. In vendor documentation, this may be called the Critical or Breakpoint Reynolds number. If left zero, the orifice will always be in turbulent flow all the way down to zero flow. You only need this value when your valve will primarily flow in the laminar regime and want its linear flow vs. pressure flow profile. Example values are:


• 20 for sharp-edge orifice,
• 80 for rounded-off orifice,
• 80 - 2300 for a short-tube orifice.
• Values > 2300 are generally not possible for orifices, but we don't limit the value.


• expansionScaleFactor: Same as GunnsFluidConductor.


• flowTuningFactor (default = 1.0, must be >= 0): This is an optional term to further tweak the valve performance if needed. Similar to the concept of tuning conductivity in regular GUNNS fluid conductors, a higher value here increases flow and a lower value decreases flow.

Input Data Parameters:

• malfBlockageFlag: Same as GunnsFluidConductor.
• malfBlockageValue: Same as GunnsFluidConductor.

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