Numerical research on drag reduction by ventilated partial cavity based on two-fluid model

Abstract

This paper presents a numerical study on the drag reduction mechanism created by a ventilated partial cavity and its associated effects by the downstream dispersed microbubbles. A semi-empirical approach is introduced to model the discrete interface of the ventilated cavity and its complex gas leakage rate induced by the local turbulent shear stress. Based on the Eulerian–Eulerian two-fluid modeling framework, a population balance approach based on MUltiple-SIze-Group (MUSIG) model is incorporated to simulate the dynamical effects of bubbly flow along the test body. Particular attention is also directed to grasp a better understanding of the size evolution of microbubble and its associated effects on drag reduction. Model predictions are validated against three experimental measurements carried out in a high-speed water tunnel by Schauer (2003) and Wosnik et al. (2005). Close examination of the flow structures, gas void fraction distributions and its resultant density ratio provides valuable insights on the complex physical phenomenon, helping to consolidate idea to maximize the drag reduction for ventilated cavitating vehicles.