.TRANSFORM.Fluid.FittingsAndResistances.Orifice

Information

Minor-loss resistance for a thin square-edged orifice plate of bore diameter diameter_orifice in a pipe of diameter dimension. The pressure loss is

dp = K*m_flow^2/(2*rho*A_pipe^2)

with the resistance coefficient referenced to the full-pipe velocity head and given by the Idelchik thin-orifice correlation (K_thinOrifice), K = [1 + 0.707√(1-a) - a]²/a² with a = (d_orifice/d_pipe)². Orifices are very lossy at small openings (a=0.5 → K≈4, a=0.2 → K≈51). Symmetric thin plate – loss is the same in either flow direction and opposes the flow. Circular cross-section; thin-plate (no bore-length friction).

References

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