Computational Investigations Into Draining in an Axisymmetric Vessel

Abstract

Within an aero-engine, bearing chamber oil is provided for components to lubricate and cool. This oil must be efficiently removed (scavenged) from the chamber to ensure that it does not overheat and degrade. Bearing chambers typically contain a sump section with an exit pipe leading to a scavenge pump. In this paper, a simplified physical situation related to bearing chamber scavenge is computationally modeled. The volume of fluid (VOF) model of Hirt and Nichols (1981, “Volume of Fluid (VOF) Method for the Dynamics of Free Boundaries,” J. Comput. Phys., 39, pp. 201–225), implemented within the commercial computational fluid dynamics (CFD) code FLUENT (Fluent, 2006, Fluent 6.3 User’s Guide, 10 Cavendish Court, Lebanon, NH 03766), has been applied to investigate the case of transient draining in an axisymmetric vessel. The model is setup to match the experimental work of Lubin and Springer (1967, “The Formation of a Dip on the Surface of a Liquid Draining From a Tank,” J. Fluid Mech., 29(2), pp. 385–390). First, a comparison of the computational predictions with the experimental results for free draining is presented. Second, a comparison between the free surface positions obtained the developed VOF methodology and the results obtained by Zhou and Graebel (1990, “Axisymmetric Draining of a Cylindrical Tank With a Free Surface,” J. Fluid Mech., 221, pp. 511–532) using a boundary integral method is reported. When comparing the results with the observations of Lubin and Springer some differences are noted. These differences, which relate to the effect of initial height and outflow history, may have arisen due to the experimental procedure used by Lubin and Springer. This paper shows that CFD is a promising approach to analyzing these simple draining situations in terms of predicting bulk quantities, transitions, and free-surface shape and position.