.TRANSFORM.Fluid.FittingsAndResistances.SmoothAdaptor

Information

Minor-loss resistance for a smooth (gradual, conical) circular adaptor connecting two pipe diameters. Unlike SharpEdgedAdaptor (an abrupt area change), this component represents a tapered transition with a finite cone angle, so the losses are substantially lower.

The pressure loss is computed as

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

referenced to the velocity head in the smaller of the two cross-sections. The coefficient K is selected by flow direction and geometry, mirroring SharpEdgedAdaptor:

• flow toward the larger diameter → gradual expansion (K_conicalDiffuser);
• flow toward the smaller diameter → gradual contraction (K_conicalConfuser).

The two directions are blended smoothly with spliceTanh around the equal-area point, and the design and reverse coefficients K_ab/K_ba are selected by the sign of the mass flow rate, so flow reversal is fully supported.

Geometry

• dimensions_ab – pipe inner diameters at port_a and port_b.
• angle – cone half-angle of the taper; the closure functions receive the total included angle 2*angle. The implied axial taper length is L = |d_b - d_a|/(2*tan(angle)).

Notes / range of validity

Circular cross-sections; turbulent-flow minor-loss correlations (Rennels & Hudson, 2012). As the half-angle approaches 90° (total angle 180°) the expansion direction reduces to the Borda-Carnot sudden-expansion limit K = (1 - beta^2)^2. Wall roughness and the laminar/turbulent transition (Re_lam, Re_turb) are honoured through the friction term.

References

Rennels, D. C. & Hudson, H. M. Pipe Flow: A Practical and Comprehensive Guide. John Wiley & Sons (2012).

Cross-check implementation: Bell, C. fluids (open-source), fluids.fittings.diffuser_conical / contraction_conical (method="Rennels").