— Orifice Plate Flow (ISO 5167)
Mass and volumetric flow through a concentric square-edged orifice plate from the measured differential pressure, qm = C/√(1−β⁴)·ε·(π/4)d²·√(2ΔPρ₁) (ISO 5167-2). Enter the discharge coefficient (Reader–Harris/Gallagher) and, for gases, the expansibility factor.