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Beginning with release v14.3, we’ve introduced new fluid conductor-like links that implement higher-fidelity flow equations.

The new orifice flow & derived links implement the orifice choked & non-choked flow theory described here, and laminar flow theory at low Reynolds numbers described here.

The picture below illustrates the difference in flow performance between the new Hi-Fi Orifice (GunnsFluidHiFiOrifice) link and the old GunnsFluidConductor link with equivalent effective conductance. The scenario is two tanks of equal volume of 1 m ³, with an hi-fi orifice and a conductor link connecting them in parallel. The orifice has a throat diameter of 0.0124 m and a C _d of 0.65. The conductor has an equivalent conductance of 7.854e-5 m ². The upstream tank/node (node 0) starts at STP of 294.261 K and 101.325 kPa. The downstream node starts at 294.261 K and 1.0 kPa. The two links begin flow simultaneously, and equalize the tank pressures in about 30 seconds.

The Flow Rate chart shows the orifice flow in blue and the conductor flow in red. The dashed vertical line denotes the point at which the hi-fi orifice transitions from choked to non-choked flow.

Laminar flow is characterized by a linear relationship between delta-pressure and flow rate. The plots below show the above case, zoomed in at the end of the flow period when the flow rate is small enough to transition into laminar flow. In this case, the hi-fi orifice is given a Critical Reynolds number of 2300. This is a higher than normal value for an orifice, but it helps to illustrate the trend of linear flow with delta-pressure:

TBD