Assessing parameters in liquid film formation

• Published in: Journal of the Brazilian Society of Mechanical Sciences and Engineering 2024, Vol.46 (1), Article 15
• Main Authors: Andrade, João Rodrigo, Lima, Bruno Silva de, Duarte, Carlos Antonio Ribeiro, Sommerfeld, Martin, Souza, Francisco José de
• Format: Article
• Language: English
• Subjects: Air flow; Boundary layer thickness; Combustion chambers; Cross flow; Droplets; Engineering; Film thickness; Finite volume method; Flat plates; Internal combustion engines; Mathematical models; Mechanical Engineering; Momentum transfer; Parameters; Shear stress; Technical Paper; Turbines; Turbulence; Turbulent flow; Unstructured grids (mathematics); Velocity distribution
• ISSN: 1678-5878; 1806-3691
• DOI: 10.1007/s40430-023-04561-8

Whether deliberate or not, liquid films may occur in many engineering applications, such as turbine combustion chambers and internal combustion engines. In this work, the formation of a thin liquid film on a flat plate in a liquid jet in air crossflow is numerically investigated through the Eulerian–Lagrange approach and the Eulerian wall film model. Simulations are performed using the finite volume method on an unstructured grid. Turbulent effects are modeled by means of the unsteady Reynolds averaged Navier–Stokes equations employing three different turbulence closure models, i.e., the k - ε , the optimized k - ε for crossflows and the shear stress transport model. The results for the liquid film thickness are validated based on experimental data whose uncertainty is known. Since the model depends on a number of operating conditions, such as the gas velocity profile and momentum flux ratio between liquid and gas, their influence is further investigated. It was found that the momentum transfer by the bombardment of impinging droplets significantly affects results and is found to be the main mechanism for the liquid transport along the bottom wall. Another important parameter is the gas inlet boundary layer thickness. This is due not only to the shear stress at the gas–liquid interface, but also to the impact on the droplet collection by the film. Also relevant is the two-way coupling between droplets and gas. It plays a fundamental role in the successful prediction of film thickness, as the liquid crossflow substantially affects the main airflow. The mechanics of the film buildup process is explored, and the different planform shapes are explained as a function of the liquid-to-gas ratios. Graphical abstract