The prediction of turbulent flows over roughened surfaces and its application to interpretation of mechanisms of horizontal annular flow

TLDR: In this article, the authors used wall functions to account for wall roughness, and verified this approach to compare their predictions with the data of Nikuradse and Hanjalic & Launder.

Abstract: It is widely believed that the secondary flow mechanism, namely the generation of secondary flow in the gas phase due to circumferentially varying interfacial roughness, plays an important role in the liquid film distribution in horizontal annular flow. We study this mechanism numerically using the HARWELLFLOW 3D computer program. We use wall functions to account for wall roughness, and verify this approach to comparing our predictions with the data of Nikuradse and Hanjalic & Launder. We then apply the methodology to the prediction of secondary flow in a pipe subjected to differential wall roughness, and show that the contribution of the secondary flow in the gas is hitherto overestimated by up to an order of magnitude.