Simple orifice restrictor sizing
Cross-section area and diameter of a simple orifice restrictor for a gas bearing, from the required flow rate and supply/restrictor/ambient pressures.
Flow rate is at normal (ambient) pressure p_A. The restrictor pressure ratio p_R/p_S is clamped to the choked-flow limit (0.53) if entered lower — flow through the orifice cannot exceed sonic velocity. The legacy page also has a Viscosity, η field, but the source only feeds it into an intermediate value that is never used by either result — it has zero effect on the outcome, so it is not exposed as an input here.
Method & references
- Gas properties (η, R, ρ, κ): Table 14.1, p. 415.
- Discharge coefficient C_d(d/l): eq. 14.2, p. 416.
The computation is a literal port of the original client-side JavaScript from /engineering-abc/calculators/d_orifice.htm. Results are verified equal to the original by an automated golden-master test. No formula has been re-derived or “improved”.