Simulation of a ship operating in an open-water ice channel

Modern ice breakers, using new technology, are now able to create channels through level ice and clean out the ice fragments, resulting in an open-water channel between two large ice sheets. Whilst this negates the potential resistance increase on a following vessel due to interacting with the broken ice pieces, the ship performance will still be influenced by the two large ice sheets on either side. The effect of such ice sheets on ships has to date not been studied in detail, so the channel effect is usually ignored during ship design processes and power estimates. The present paper reports on work to develop a computational model to simulate a ship advancing in an open-water ice channel and investigate the associated ship-wave-ice interaction. Based on a series of simulations, this work how the ship resistance and wake change with ship speed, channel width and ice thickness

Numerical analysis of shipping water impacting a step structure

Shipping water, the flow washing over and impacting the upper decks of ships and offshore structures, occurs frequently during their service life and often causes structural problems. For engineers to design safe floating structures subjected to shipping water it is essential to gain an in-depth understanding of its depth and flow field, and the resulting impact forces. In this work, Computational Fluid Dynamics (CFD) is applied to understand the physics of shipping water washing over a stepped platform. We find that the most accurate solutions are obtained with the turbulence closure. The hydrodynamic load generated by the shipping water is found to strongly depends on the kinematic energy of the water hitting the step. It is shown that with smaller values of the freeboard a more dynamic flow ensues, with a stronger vortex and larger velocity gradient resulting in deeper shipping water and a larger impact force

Numerical simulation of hydroelastic waves along a semi-infinite ice floe

With the increasing demand for Arctic Engineering purposes, Squire suggests current theories may have oversimplified the sea ice hydroelasticity, indicating the need to develop numerical models to obtain more realistic solutions. Numerical models have been reported capable of achieving a full coupling between waves and rigid floating ice. When an ice floe is relatively small to wavelength, it is valid for the floe to be considered as rigid, thus no need to solve ice deformations. However, in order to model the sea ice hydroelasticity, a Fluid-Structure Interaction (FSI) approach is required to obtain the structural solution of ice deformation and couple it with the solution of surrounding fluid domain, which requires further development of above models. To fill this gap, an FSI approach was developed based on the open-source code, OpenFOAM, and it has been validated in the case of wave interaction with a finite ice floe. In this work, the developed model is extended to a very long ice floe to study the semi-infinite scenario. Simulations are performed to present the wave-induced ice deformation, with the attenuation of hydroelastic waves along the ice floe investigated

Letter: Hydroelastic interactions between water waves and floating freshwater ice

Hydroelastic interactions between regular water waves and floating freshwater ice are investigated using laboratory experiments for a range of incident wave periods and steepnesses. It is shown that only incident waves with sufficiently long period and large steepness break up the ice cover and that the extent of breakup increases with increasing period and steepness. Furthermore, it is shown that an increasing proportion of the incident wave propagates through the ice-covered water as the period and steepness increase, indicating the existence of a positive feedback loop between the ice breakup and increased wave propagation

Interactions between Irregular Wave Fields and Sea Ice: A Physical Model for Wave Attenuation and Ice Breakup in an Ice Tank

Irregular, unidirectional surface water waves incident on model ice in an ice tank are used as a physical model of ocean surface wave interactions with sea ice. Results are given for an experiment consisting of three tests, starting with a continuous ice cover and in which the incident wave steepness increases between tests. The incident waves range from causing no breakup of the ice cover to breakup of the full length of ice cover. Temporal evolution of the ice edge, breaking front, and mean floe sizes are reported. Floe size distributions in the different tests are analyzed. The evolution of the wave spectrum with distance into the ice-covered water is analyzed in terms of changes of energy content, mean wave period, and spectral bandwidth relative to their incident counterparts, and pronounced differences are found between the tests. Further, an empirical attenuation coefficient is derived from the measurements and shown to have a power-law dependence on frequency comparable to that found in field measurements. Links between wave properties and ice breakup are discussed.Giulio Passerotti, Luke G. Bennetts, Franz von Bock und Polach, Alberto Alberello, Otto Puolakka, Azam Dolatshah, Jaak Monbaliu, and Alessandro Toffol

Wave attenuation due to ice cover:An experimental model in a wave-ice flume

Waves penetrate deep into the ice covered seas, inducing breakup of the ice cover. Concomitantly, the ice cover attenuates the wave energy over distance, so that wave impacts die out eventually. Observations of wave attenuation and concurrent wave-induced breakup in the literature are serendipitous due to difficulties in making measurements in ice covered seas. Hence understanding of wave-ice interactions remain uncertain. Here we present measurements of wave propagation through ice covered waters in the new experimental wave-ice facility at the University of Melbourne. The facility comprises of a 14m long and 0.76m wide flume in a refrigerated chamber, where temperatures can be lowered down to-12 degrees Celsius to generate a continuous ice cover on the water surface. A wave maker, installed at one end, is used to generate regular waves, ranging from gently-sloping to storm-like conditions. Wave attenuation rates are determined from video-camera images of the displacements of markers embedded in the ice cover. The experiments investigated wave propagation through the continuous ice cover, breakup, and propagation through the broken ice cover. Spatial evolution of the breakup and geometrical properties of floes are monitored and correlated with incident wave properties. Wave attenuation over broken ice is investigated and compared against the continuous ice case

Numerical analysis of shipping water impacting a step structure

Shipping water, the flow washing over and impacting the upper decks of ships and offshore structures, occurs frequently during their service life and often causes structural problems. For engineers to design safe floating structures subjected to shipping water it is essential to gain an in-depth understanding of its depth and flow field, and the resulting impact forces. In this work, Computational Fluid Dynamics (CFD) is applied to understand the physics of shipping water washing over a stepped platform. We find that the most accurate solutions are obtained with the k−ε turbulence closure. The hydrodynamic load generated by the shipping water is found to strongly depends on the kinematic energy of the water hitting the step. It is shown that with smaller values of the freeboard a more dynamic flow ensues, with a stronger vortex and larger velocity gradient resulting in deeper shipping water and a larger impact force.QC 20220318</p