Direct Numerical Simulation of a Thin Shear-Driven Water Film under Turbomachinery Relevant Conditions

Thin shear-driven films have many applications. They appear on airfoils of aircrafts or wind turbines during heavy rain. They also appear in stationary gas turbines, when fogging/high fogging is applied. Well defined film models and coupling conditions between the gas flow and the film flow are necessary to consider the influence of the liquid films in these applications. In this study, a setup of a Direct Numerical Simulation (DNS) is presented, which will be used to investigate thin liquid films. First, a film model from the literature is presented and its coupling conditions between the gas flow and the film flow are discussed. Then, the numerical setup and boundary conditions are explained, which are used to investigate the coupling conditions. A simulation with a film Reynolds number of 50 and a gas Reynolds number (defined with the boundary layer thickness) of 54000 is performed. The numerical prediction is accomplished with the in-house program Free Surface 3D (FS3D), which uses the Volume of Fluid (VOF) method for the interface tracking and the Piecewise Linear Interface Calculation (PLIC) for the surface reconstruction. Instantaneous and time averaged results of the volume fraction, velocity field and shear stress are presented. The results show that DNS enables the investigation of the coupling conditions at the gas-liquid interface.