73 research outputs found
Water wave transmission by an array of floating disks
An experimental validation of theoretical models of transmission of regular
water waves by large arrays of floating disks is presented. The experiments are
conducted in a wave basin. The models are based on combined potential-flow and
thin-plate theories, and the assumption of linear motions. A low-concentration
array, in which disks are separated by approximately a disk diameter in
equilibrium, and a high-concentration array, in which adjacent disks are almost
touching in equilibrium, are used for the experiments. The proportion of
incident wave energy transmitted by the disks is presented as a function of
wave period, and for different wave amplitudes. Results indicate that the
models predict wave energy transmission accurately for small-amplitude waves
and low-concentration arrays. Discrepancies for large-amplitude waves and
high-concentration arrays are attributed to wave overwash of the disks and
collisions between disks. Validation of model predictions of rigid-body motions
of a solitary disk are also presented
Reflection and transmission of ocean wave spectra by a band of randomly distributed ice floes
A new ocean wave/sea-ice interaction model is proposed that simulates how a
directional wave spectrum evolves as it travels through an arbitrary finite
array of circular ice floes, where wave/ice dynamics are entirely governed by
wave scattering effects. The model is applied to characterise the wave
reflection and transmission properties of a strip of ice floes, such as an ice
edge band. A method is devised to extract the reflected and transmitted
directional wave spectra produced by the array. The method builds upon an
integral mapping from polar to Cartesian coordinates of the scattered wave
components. Sensitivity tests are conducted for a row of floes randomly
perturbed from a regular arrangement. Results for random arrays are generated
using ensemble averaging. A realistic ice edge band is then reconstructed from
field experiments data. Simulations show a good qualitative agreement with the
data in terms of transmitted wave energy and directional spreading. In
particular, it is observed that short waves become isotropic quickly after
penetrating the ice field
An idealised wave-ice interaction model without subgrid spatial and temporal discretisations
A modified version of the wave-ice interaction model proposed by Williams et
al (2013a,b) is presented for an idealised transect geometry. Wave attenuation
due to ice floes and wave-induced ice fracture are both included in the
wave-ice interaction model. Subgrid spatial and temporal discretisations are
not required in the modified version of the model, thereby facilitating its
future integration into large-scaled coupled models. Results produced by the
new model are compared to results produced by the original model of Williams et
al (2013b).Comment: 8 pages, 3 figure
Surge motion of an ice floe in waves: comparison of theoretical and experimental models
A theoretical model and an experimental model of surge motions of an ice floe
due to regular waves are presented. The theoretical model is a modified version
of Morrison's equation, valid for small floating bodies. The experimental model
is implemented in a wave basin at scale 1:100, using a thin plastic disk to
model the floe. The processed experimental data displays a regime change in
surge amplitude when the incident wavelength is approximately twice the floe
diameter. It is shown that the theoretical model is accurate in the large
wavelength regime, but highly inaccurate for the small wavelength regime.Comment: 11 pages, 10 figure
A thin plate approximation for ocean wave interactions with an ice shelf
A variational principle is proposed to derive the governing equations for the
problem of ocean wave interactions with a floating ice shelf, where the ice
shelf is modelled by the full linear equations of elasticity and has an
Archimedean draught. The variational principle is used to form a thin-plate
approximation for the ice shelf, which includes water--ice coupling at the
shelf front and extensional waves in the shelf, in contrast to the benchmark
thin-plate approximation for ocean wave interactions with an ice shelf. The
thin-plate approximation is combined with a single-mode approximation in the
water, where the vertical motion is constrained to the eigenfunction that
supports propagating waves. The new terms in the approximation are shown to
have a major impact on predictions of ice shelf strains for wave periods in the
swell regime.Comment: 19 pages, 7 figure
Model predictions of wave overwash extent into the marginal ice zone
A model of the extent of wave driven overwash into fields of sea ice floes is
proposed. The extent model builds on previous work modelling wave overwash of a
single floe by regular waves by including irregular incoming waves and random
floe fields. The model is validated against a laboratory experiment. It is then
used to study the extent of wave overwash into marginal ice zones consisting of
pancake and fragmented floe fields. The effects of wave conditions and floe
geometry on predicted extents are investigated. Finally, the model is used to
predict the wave overwash extent for the conditions observed during a winter
(July) 2017 Antarctic voyage in which the sea surface was monitored by a
stereo-camera system
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