.TRANSFORM.Fluid.ClosureRelations.PressureLoss.Functions.Orifices.K_thinOrifice

Information

Resistance coefficient for a thin sharp-edged orifice (single bore) or a perforated plate (use the total open-area ratio) in a straight pipe, per Idelchik:

K = [1 + 0.707·√(1 - a) - a]² / a²

where a is the free-area ratio (open area / full pipe area), and K is referenced to the velocity head in the full pipe cross-section, i.e. used as dp = K·m_flow²/(2ρA_pipe²). The form encodes the vena-contracta contraction followed by sudden expansion; e.g. a=0.5 → K≈4.0, a=0.2 → K≈51 (orifices are very lossy at small openings). For a thick (long-bore) orifice an additional bore-friction term would apply; this function is the thin-plate limit.

References

Idelchik, I. E. Handbook of Hydraulic Resistance, Begell House.

Interface

function K_thinOrifice
  extends TRANSFORM.Icons.Function;
  input Real ar(min = 0, max = 1) "Free-area ratio = open area / full pipe area";
  output Units.NonDim K "Resistance coefficient";
end K_thinOrifice;