Author(s): Yan Liu; Thorsten Stoesser

Linked Author(s): Yan Liu

Keywords: Large eddy simulation; Partially filled pipe flow; Free surface flow; Secondary current

Abstract: This paper provides details of the physical mechanisms that lead to the so-called ‘velocity dip’ in partially-filled pipe flows and reveals the interactions between the water surface and the turbulent flow underneath it. Therefore, large eddy simulations of a semi-filled pipe are performed. It is observed that a single pair of symmetric vortices about the vertical pipe bisector forms as a result of the wall-water surface junction turbulence anisotropy. At this wall-water surface junction, imbalance of the production, dissipation and transport of turbulent kinetic energy (TKE) leads to non-zero TKE convection, which drives the secondary flow. The distribution of the instantaneous velocity reveals the signatures of wall-bounded turbulent flows near the pipe wall such as large-scale motions and associated hairpin vortices which are convected towards the water surface. Free surface fluctuations are observed which are caused by these hairpin vortices reaching the water surface.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022115

Year: 2022