S Denehy

Influence of restricted water on the time domain interaction forces and moment on a berthed ship due to a passing ship

Abstract An investigation was conducted into the effect that different berthed ship bow and stern blockage arrangements has on the interaction forces and moment experienced by a berthed ship due to a passing ship. Physical scale model experiments were used to quantify the magnitude and form of the interaction forces and moments for five different blockage arrangements. The interaction force and moment traces from the experiments were compared to traces predicted using existing empirical formulae based on open water scenarios. Additionally, two methods were used to adjust idealised curves using the experimental results to better represent the form and magnitude of the interaction forces and moments. To demonstrate the effect that the changes in form and magnitude of the interaction forces and moments has on the predicted berthed ship motions the interaction forces and moment from the physical scale model experiments, empirical predictions and the adjusted idealised curves were extrapolated to represent a full scale ship and used as input to a commercially available time domain numerical simulation code to predict the berthed ship motions. The bow and stern blockage was shown to have a significant effect on both the form and magnitude of the interaction forces and moments, and hence, the predicted berthed ship motions. The empirically predicted interaction forces and moments correlated poorly with the experimental results.

URANS prediction of berthed ship–passing ship interactions

ABSTRACT This paper investigates berthed ship–passing ship hydrodynamic interactions using unsteady Reynolds-averaged Navier–Stokes (URANS) solver StarCCM+ in both model scale and full scale. A double-body approximation method is adopted to investigate the hydrodynamic effects on the berthed ship when in close proximity with the passing ship. A benchmark experimental test condition is replicated for the verification and validation of the numerical simulation. Based on the validated numerical model, the interaction forces and moments are predicted for different passing ship speeds and lateral separations. The same conditions are repeated in full scale to quantify possible scale effects. The trends seen in the numerical results correlated well with past authors findings. The difference in the model-scale and full-scale interaction force and moment predications are not significant. Full scale berthed ship–passing ship interaction forces and moments can therefore be approximated (for similar cases) by model-scale tests with confidence. HIGHLIGHTS (1) URANS computations are conducted to study berthed ship–passing ship interactions in both full-scale and model-scale conditions.(2) Numerical results are validated against benchmark experimental data.(3) Relationship between interaction forces and moments acting on the berthed ship with respect to passing ship speed and lateral separation are identified.(4) Scale effects in berthed ship–passing ship interaction forces and moments are quantified.

An experimental study of ship motions during replenishment at sea operations between a supply vessel and a landing helicopter dock

Hydrodynamic interactions during Replenishment at Sea (RAS) operations can lead to large ship motions and make it difficult for vessels to maintain station during the operation. A research program has been established which aims to validate numerical seakeeping tools to enable the development of enhanced operator guidance for RAS. This paper presents analysis of the first phase of scale model experiments and focuses on the influence that both the lateral and longitudinal separations between two vessels have on the interactions during RAS. The experiments are conducted in regular head seas on a Landing Helicopter Dock (LHD) and a Supply Vessel (SV) in intermediate water depth. The SV is shorter than the LHD by approximately 17%, but due to its larger block coefficient, it displaces almost 16% more than the LHD. Generally, the motions of the SV were larger than the LHD. It was found that hydrodynamic interactions can lead to large SV roll motions in head seas. Directions for future work are provided.

URANS prediction of berthed ship - passing ship interactions

In this paper, the unsteady Reynolds-Averaged Navier-Stokes computational method has been employed for investigating the hydrodynamic interactions between berthed and passing ships. Initially, simulations in model-scale were performed for validating the numerical modelling technique using available benchmark experimental test cases. A formal study of verification and validation was carried out for quantifying the numerical uncertainties. Based on the validated numerical setup, systematic computations were conducted for further investigations on the influence of varying passing ship speeds and lateral separations on the interaction forces and moments. The same conditions were repeated in full scale to quantify possible scale effects. The numerical results demonstrate that the interaction forces and moments are proportional to the square of the passing ship speed and inversely proportional to the lateral separation between the two ships, which agrees well with the findings by Remery (1974) and Kriebel (1995) respectively. In addition, when comparing model and full scale results, the overall differences are not very significant and are within the simulation uncertainty for most cases

Squat in Berthed Ship - Passing Ship Interaction for Restricted Water Cases

This paper presents a study on berthed ship – passing ship interaction for two different channel widths using physical model scale physical experiments and Computational Fluid Dynamics (CFD). The interaction forces and moment and the sinkage of the berthed ship were measured for the two different channel widths. In order to determine the effect that the additional blockage caused by the berthed ship had on the squat of the passing ship, the squat was also measured under the same conditions as in the ship interaction scenarios, but without the presence of berthed ship. The two restricted water cases were replicated in model scale using 3D inviscid double body CFD simulations and validated against experimental results. The CFD models were run with the passing ship fixed in the static level trim condition as well as with the passing ship fixed at the running sinkage and trim condition measured from the physical model scale experiments to determine whether the latter would improve correlation with the experimental results.