Improved Prediction of Sheet Cavitation Inception Using Bridged Transition Sensitive Turbulence Model and Cavitation Model

Sheet cavitation inception can be influenced by laminar boundary layer flow separation under Reynolds numbers regimes with transitional flow. The lack of accurate prediction of laminar separation may lead to massive over-prediction of sheet cavitation under certain circumstances, including model scale hydrofoils and marine propellers operating at relatively low Reynolds number. For non-cavitating flows, the local correlation based transition model, γ−Reθ transition model, has been found to provide predictions of laminar separation and resulting boundary layer transition. In the present study, the predicted laminar separation using γ−Reθ transition model is bridged with a cavitation mass transfer model to improve sheet cavitation predictions on hydrofoils and model scale marine propellers. The bridged model is developed and applied to study laminar separation and sheet cavitation predictions on the NACA16012 hydrofoil under different Reynolds numbers and angles of attack. As a reference case, the open case of the PPTC VP1304 model scale marine propeller tested on an inclined shaft is studied. Lastly as an application case, the predictions of cavitation on a commercial marine propeller from Kongsberg is presented for model scale conditions. Simulations using the bridged model and the standard unbridged approach with k−ωSST turbulence model are performed using the open-source package OpenFOAM, both using the Schnerr–Sauer cavitation mass transfer model, and the respective results are compared with available experimental results. The predictions using the bridged model agree well compared to experimental measurements and show significant improvements compared to the unbridged approach.

STUDY OF FLUID DYNAMICS AND SULFUR MASS TRANSFER BETWEEN STEEL AND SLAG IN A LADLE FURNACE CONSIDERING DRAG AND NON-DRAG FORCES

In this work fluid dynamics and a basic study of the sulfur transfer at the steel/slag interface in the ladle during argon gas agitation was developed. Mass transfer and chemical reaction models coupled with Computational Fluid Dynamics (CFD) were employed. The multiphasic simulation was solved using the Eulerian model considering drag and non-drag forces, and the flow pattern was validated through Particle Image Velocimetry (PIV) technique. The sulfur transfer rate was tracked by two approximations: (1) unidirectional constant rate Mass Transfer Model (MTM), and (2) unidirectional constant rate Mass Transfer Model coupled with Chemical Reaction Model (MTM+CRM) using Arrhenius equation. It was found that including the non-drag forces affects the fluid dynamics structure. Otherwise, the desulfurization rates increase as the argon gas flow rate increases, finding that the MTM model predicts ~15% less sulfur in the steel than the MTM+CRM, whose results were compared with plant measurements reports.