Numerical investigation of turbulent flow and thermal behaviour in helical pipes

Abstract

Fluid flow in helical pipe is associated with a wide range of engineering applications that motivate significant interest for research in this field. Flow in helical pipes has unique behaviour, where both mean flow and boundary layer are influenced by secondary vortices. Numerical modelling of such flow field requires specific considerations to ensure robust and reliable simulation of fluid structures. Choosing a numerical turbulent scheme, in the spectrum of algebraic closures to DNS, is a compromise between resolution of turbulence effects and computational resources. This study applies a selection of URANS, RSM, LES and hybrid turbulence models (DES and SAS) for CFD analysis of flow and heat transfer in a helical pipe. Experimental measurements are utilised as validation benchmark to assess the accuracy of models and refinement level of turbulence scale, essential for this specific application. Wall grid refinements are also examined to highlight essential y+ requirements associated with thermal boundary layer estimations. Turbulence models are evaluated for their accuracy in capturing secondary flow (as the main mean flow feature) and also boundary layer characteristic, which are critical for convective heat transfer. Using FLUENT as a well-trusted commercial code, the validity and performance of turbulence models are investigated and compared to suggest accurate, yet cost-effective model for the flow field affected by centrifugal force.