A 2D+t approach for the transverse viscous loads in a modular maneuvering model

Abstract

The importance of the transverse viscous loads, in a modular maneuvering model, is investigated. A method to estimate steady sectional drag coefficients is first presented. A 2D+t approach, which accounts for forward-speed effects, is also presented. The time-varying drag coefficients, in the 2D+t method, are estimated with three methods: two simplified methods using results from the literature directly, and one more sophisticated method which uses time-derivatives, from time-dependent drag coefficients for hull forms in the literature, and integrates the drag coefficients along the hull. Turning circles with 25 and 35 rudder angle are simulated in calm water and regular waves for a range of wavelengths between and 1.120, with wave steepness , and initial head sea. The Duisburg Test Case (DTC) is used as a test ship. The numerical simulations are compared with free-running model tests. Overall, the 2D+t method, with integrated drag coefficients, shows a better match with the experiments compared to the cross-flow approach. However, both methods capture the main trends considering tactical diameter and advance for the tested wave conditions. Furthermore, using scaled time-varying drag coefficients for a circular cylinder can be a good starting point in a 2D+t approach.