Torsion effect on the flow in a helical pipe

The effect of curvature and torsion on the flow in a helical pipe of circular cross-section is studied numerically by the spectral method. The calculations are carried out for 0 ≤ δ ≤ 0.6, 0 ≤ β₀ ≤ 1.4 and 500 ≤ D_n≤ 2000, where δ is the non-dimensional curvature,β₀ the ratio of torsion to square root of curvature, and D_n the Dean number. The results obtained indicate large effects of torsion on the flow: The conventional two-vortex secondary flow is distorted to become almost one single recirculating cell when β₀ {greater-than or approximate} 0.8. The flux through the pipe at the given Dean number and curvature first decreases from that of the toroidally curved pipe as β0 increases from zero, reaches a minimum at β₀ ≈ 0.8, and then increases to values larger than that of the toroidally curved pipe. The minimum value decreases as ° increases.