Numerical Simulation of Dam-Break Problem Using an Adaptive Meshing Approach

Abstract The numerical simulation of free-surface flows is a vast topic, with applications to various fields of engineering such as aerospace, automotive, nuclear, etc. The Volume of Fluid (VOF) method represents a suitable technique to simulate free surface flows, tracking the air-liquid interface within the calculation domain. However this method requires a very fine mesh to successfully reconstruct the liquid surface, leading to very high computational costs. In this paper, VOF simulations of three-dimensional dam-break problem have been carried out using an adaptive meshing approach. Unsteady calculations have been performed exploiting the adaptive mesh feature implemented in ANSYS Fluent. In particular, a grid adaptation strategy has been defined as a way of significantly reducing the numerical effort. The main idea is to keep high resolution only locally at the air-liquid interface, minimizing numerical diffusion, and to maintain a coarse mesh size elsewhere. The dam-break problem was analyzed because it has been widely studied experimentally and numerically, representing a benchmark problem for verifying numerical models involving free-surface flows. The accuracy of the method has been assessed comparing simulation results with experimental data

High Speed Visualizations of oil Jet Lubrication for Aero-engine Gearboxes☆

Abstract Augmenting gearing systems efficiency is a key issue in developing innovative aero-engines with low specific fuel consumption. The transmission system directly affects the engine overall efficiency, therefore it is essential maximizing its performance. In high speed applications fluid-dynamic losses become predominant and are directly connected to the lubrication method. Oil jet systems are generally used in order to achieve a proper cooling and lubrication of tooth surface. A novel rotating test rig was exploited for investigating oil jet lubrication by means of high speed visualizations. An oil jet impinging radially on a single spur gear was generated by a spray-bar, assessing which parameters affect the oil jet behavior

Numerical Simulation of Oil Jet Lubrication for High Speed Gears

The Geared Turbofan technology is one of the most promising engine configurations to significantly reduce the specific fuel consumption. In this architecture, a power epicyclical gearbox is interposed between the fan and the low pressure spool. Thanks to the gearbox, fan and low pressure spool can turn at different speed, leading to higher engine bypass ratio. Therefore the gearbox efficiency becomes a key parameter for such technology. Further improvement of efficiency can be achieved developing a physical understanding of fluid dynamic losses within the transmission system. These losses are mainly related to viscous effects and they are directly connected to the lubrication method. In this work, the oil injection losses have been studied by means of CFD simulations. A numerical study of a single oil jet impinging on a single high speed gear has been carried out using the VOF method. The aim of this analysis is to evaluate the resistant torque due to the oil jet lubrication, correlating the torque data with the oil-gear interaction phases. URANS calculations have been performed using an adaptive meshing approach, as a way of significantly reducing the simulation costs. A global sensitivity analysis of adopted models has been carried out and a numerical setup has been defined

High Speed Visualizations of oil Jet Lubrication for Aero-engine Gearboxes

Abstract Augmenting gearing systems efficiency is a key issue in developing innovative aero-engines with low specific fuel consumption. The transmission system directly affects the engine overall efficiency, therefore it is essential maximizing its performance. In high speed applications fluid-dynamic losses become predominant and are directly connected to the lubrication method. Oil jet systems are generally used in order to achieve a proper cooling and lubrication of tooth surface. A novel rotating test rig was exploited for investigating oil jet lubrication by means of high speed visualizations. An oil jet impinging radially on a single spur gear was generated by a spray-bar, assessing which parameters affect the oil jet behavior