Numerical Modelling of VOF to Investigate Ventilation in High-Speed Craft

Published in: ICSOT 2023 conference

Authors: K S Srinivas, J Ram Kumar, Sharad S Dhavalikar

Date of Publication: December 8-9, 2023

The focus of the present study is to investigate the performance of high-speed craft and estimate the resistance at higher Froude number. The accurate estimation of resistance is very important to estimate the powering requirements. With the recent developments in Computational Fluid Dynamics (CFD) both in terms of numerical models and the computational resources, there is a widespread use of CFD for marine applications. The critical modelling parameter which makes the problem complex is accurate modelling and resolution of free-surface to model the air water interface. Volume of Fluid (VOF) method was widely used to resolve the interface of air water mixture. In the case of high-speed craft when the vessel enters into the planning regime there may be a numerical error induced due to the smearing of interface. This error will lead to change in the wetted surface area which will result in an error in resistance estimate. This is generally termed as numerical ventilation and attention is needed to resolve this problem. Our study primarily focusses on addressing this problem by accurate modelling of prism layers on the hull to minimize the numerical ventilation. A modified High-Resolution Interface Capturing (HRIC) scheme which uses the concept of Slip Velocity was used to model the interface on the hull. The slip relative velocity helps in recovering smeared interface between two phases. There are various guidelines available for performing basic resistance CFD simulations for displacement hulls, from ITTC discussions are made towards the recommended best practices to predict the resistance for a HSC and numerical results are validated with experiments.