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 λ∕Lpp=0.281 and 1.120, with wave steepness H∕λ=1∕40, 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.