Author(s): Janek Laanearu

Linked Author(s): Janek Laanearu

Keywords: No Keywords

Abstract: This study presents an endeavour to parameterise the hydraulic-type solutions of air-water stratified flow in a sloped pipe. The airflow velocity is coupled with the water-flow velocity through interfacial drag in the gravity pipe, using an air-part force-balance equation that includes frictional and pressure-gradient terms. It is shown that if the fluids (air and water) are specifically coupled in terms of gravity, and wet and dry pipe-wall skin friction, then the stratified flow develops, where the air flow inside the pipe interior head space is purely driven by water flow below, i.e. the fluxes are related to the gravity-driven water flow. The Manning roughness scale is related to the Colebrook-White formula friction factor to determine the pipe wall roughness height for varying hydraulic radius. The air-flow force-balance equation solutions, which depend on the frictional and pressure-gradient terms, are coupled with the Manning equation solutions to relate the water-flow fluxes to the air-flow fluxes in a simplified manner, given the air-water interfacial drag without a pressure-gradient term.

DOI:

Year: 2026