Numerical investigation of gravitational effects in horizontal annular liquid–gas flow

In this work, exploratory numerical simulations of liquid–gas flows in horizontal pipes are conducted for three different sets of conditions in the annular and stratified-annular flow regimes. Careful dimensional analysis is used to choose governing parameters in a way that yields flows that are relevant to realistic engineering applications, while remaining computationally tractable. Statistics of the velocity field and height of the liquid film are computed as a function of circumferential location in the pipe, demonstrating the existence of a viscous sublayer within the liquid film, as well as a viscous layer near the interface and a log law region within the gas core. The probability of dry-out conditions at the wall in upper regions of the pipe is shown to increase as gravitational effects increase. Circumferential motion of the liquid and gas phases within the pipe cross section are analyzed, informing possible mechanisms for sustainment of the liquid film. A simple model is developed that helps to characterize the dynamics of the liquid annulus and aids in understanding the effect of secondary gas flow on the circumferential motion of the film. Void fraction, film height, and film asymmetry are compared with experimental correlations available in