.TRANSFORM.Fluid.FittingsAndResistances.Entrance

Information

Minor-loss resistance for the entrance of a pipe drawing from a large plenum/reservoir. The pressure loss is

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

referenced to the pipe velocity head, with a user-supplied entrance loss coefficient K. Typical values:

• sharp-edged (flush): K ≈ 0.5 (Idelchik/Crane) – default; Rennels recommends 0.57;
• slightly rounded: K ≈ 0.2–0.25; well-rounded / bellmouth: K ≈ 0.03–0.05;
• re-entrant (Borda, protruding): K ≈ 0.78–1.0;
• beveled (45°, moderate): K ≈ 0.2–0.3.

The loss opposes the flow (design direction is plenum → pipe). Circular cross-section.

References

Idelchik, I. E. Handbook of Hydraulic Resistance, Begell House; Rennels & Hudson, Pipe Flow (2012).