1,721,012 research outputs found
DISCUSSION OF "IMPACT OF COEFFICIENTS IN MOMENTUM EQUATION ON SELECTION OF INERTIAL MODELS"
No full textquesto articolo è una discussion e non ha abstrac
Partial standing waves on a steep slope
No full textMeasured free surface elevations and horizontal velocities of non-breaking regular waves on a 1:2 rough permeable
slope are analyzed to examine the cross-shore variations of the incident and reflected waves on the steep slope. The
co-located measurements of the free surface elevation and horizontal velocities at a number of elevations are used to
separate the incident and reflected waves locally. The estimated partial standing waves are then shown to describe
the local free surface elevation and horizontal velocity reasonably well. The incident wave energy flux is found to be
approximatelyc onstant along the 1:2 slope, whereas the data and linear theory are not accuratee nough to detect the
cross-shore variation of the relative small wave reflection coefficient. The measured mean horizontal velocities are
shown to be in qualitative agreement with the return current estimated from the separated incident and reflected
waves
Spar Buoy numerical model calibration and verification
No full textThe present paper describes the experiences gained from the design methodology and operation of a 3D physical model experiment aimed to investigate the dynamic behavior of a spar buoy (SB) off-shore floating wind turbine (WT) under different wind and wave conditions.
The physical model tests have been performed at Danish Hydraulic Institute (DHI) off-shore wave basin within the European Union-Hydralab IV Integrated Infrastructure Initiative, in October 2012. The floating WT model has been subjected to a combination of regular and irregular wave attacks and steady wind loads. Observations of hydrodynamics, displacements of the floating structure, wave induced pressures and tensions at critical points of the structure and at the mooring lines have been carried out. Based on the observed data, the numerical model Sesam [1], developed by Det Norske Veritas (DNV), has been calibrated and verified. The adopted numerical model took into account the wave induced response and the effects of the mooring lines on the overall system.
The calibration of the numerical model has been performed both for static and dynamic conditions.
At the end of the calibration procedure, the numerical model has been successfully used to simulate two selected irregular wave attack
Wave flume investigation on different mooring systems for floating breakwaters
No full textThis paper investigates on different types of mooring systems for floating breakwaters
(FBs): chains with different initial tensions or piles. The principal aim is to describe the
wave transmission and the statistics of the loads on the moorings. The latter analysis is
particularly innovative because it defines in the details the condition of snapping, that can
be reached along the chains and is frequent in many practical cases. Physical model tests
have been carried out in the wave flume of the Maritime Laboratory of the University of
Padova. The tested structure resembles typical FBs located in Italian lakes in scale 1:10.
Regular and irregular waves were generated. Stiffness of the mooring systems was
modified by varying the initial stress and the results obtained by the tests are in depth
described. Simple numerical simulations, based on irrotational flow, which are commonly
used for design of moorings, were seen not to be suitable to describe the maximum loads.
The added value of a more detailed investigation, in particular by means of physical
testing, is established
Wave reflection for composite slopes
No full textThis paper analyses wave reflection from composite slopes by means of an extensive database,
which includes smooth and rock (permeable and impermeable core) slopes and slopes with all kind
of artificial armour units. The aim of this research was to identify the proper evaluation of the
breaker parameter so that the formula the Authors already developed for straight slopes could be
applied also to structures with berms, toes and in general to composite slopes. The correct
evaluation of the breaker parameter is focused on a more accurate estimation of the structure slope.
Based on the observation that for reflection, differently from what happens for overtopping and runup,
the whole slope below m.sl. is really important, the slope to appear in the breaker parameter is
evaluated as a weighted average of the partial slopes and it is included in the proposed prediction
formula, obtaining a good agreement with the original database for straight slopes
Effect of layout on floating breakwater performance: results of wave basin experiments
No full textAim of this contribution is to investigate the relevance of the layout on the performance
of floating breakwater schemes under oblique waves. An experimental investigation was
carried out in the wave basin of the Maritime Laboratory of Padua University, Italy. The
facility dimensions are 3.8m x 20.6m x 0.8m. Several regular and irregular longcrested
waves were generated and two different layouts (I- and J-shaped) and three obliquities
(0°, 30°, 60°) were tested. With increasing wave obliquity, wave transmission decreases,
mooring forces due to snapping decrease and link forces slightly increase. The J-shaped
configuration determines basically the same effects with regards to both transmission
and loads. The maxima of link forces are not much greater than the average loads and
this is relevant for fatigue and reliability considerations
Piling-up and rip-currents induced by low-crested structures in laboratory and prototype.
No full textThe paper aims at providing a simple model for evaluating piling-up, overtopping, filtration and rip currents for low crested structures. The model is essentially based on mass and momentum balance and on resistance laws that relate piling-up and mass fluxes. A procedure is suggested and validated against 2D and 3D experimental data. This procedure is innovative with respect to existing formulations since it applies both to emerged and submerged structures and it simultaneously accounts for structure permeability, return flow through gaps and dissipative effects
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