Secondary vortex-based analysis of flow characteristics and pressure drop in helically coiled pipe

This article presents an investigation for the secondary flow characteristics and associated pressure loss in fluid flow through helically coiled pipe. Computational fluid dynamics is employed to analyze the pipe flow with various geometries, and the accuracy of the numerical methodology is validated by conducting corresponding experiments. The analysis performs a detailed parametric study involving the pressure loss, the secondary vortex motion, and the secondary vortex intensity for a range of coil diameters (D; ranging from 300 to 3000 mm) and pipe diameters (d; ranging from 50 to 90 mm). The pipe flow develops to a stable state with increase in coil diameter, while an increase in pipe diameter delays this development. Then, the secondary flow characteristics are analyzed to explore the pressure loss mechanism. The distorted streamline of secondary vortices and the enlarged deflection angle of secondary vortices are both factors contributing to the enhanced pressure loss. Furthermore, the effects of pipe flow development on the following flow characteristics such as the turbulence dissipation rate and the secondary vortex intensity are revealed. These characteristics all distribute regularly and reach lower values when pipe flow begins to a stable state.