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Introduction
Published in Srinivasan Chandrasekaran, Offshore Semi-Submersible Platform Engineering, 2020
Airy’s theory, which assumes linearity between the wave height and kinematic quantities, is commonly used in the theories listed above. The regular waves are usually defined by their wave height (H) and wave period (T), as shown in Figure 1.2. For determining the wave forces on offshore structures, the wave surface profile should be idealized. Any one of the above mentioned appropriate wave theories should be used to compute the water particle kinematics. The applicability of wave theory is based on a wide range of parameters, including the wave height, water depth, and wave period. It is not always possible to select the wave theory precisely suitable for the selected condition. Airy’s small-amplitude linear wave theory is valid for deep water conditions where (d/gT2) > 0.8, and Stokes theory should be used when (H/gT2) > 0.04.
Anisotropic Materials
Published in Daniel Malacara-Hernández, Brian J. Thompson, Advanced Optical Instruments and Techniques, 2017
The first of these is called the wave surface. As a light wave from a point source expands through space, it forms a surface that represents the wavefront. This surface is composed of points having equal phase. At a particular instant in time, the wave surface is a representation of the velocity surface of a wave expanding in the medium; it is a measure of the distance through which the wave has expanded from some point over some time period. Because the wave will have expanded further (faster) when experiencing a low refractive index and expanded less (slower) when experiencing a high index, the size of the wave surface is inversely proportional to the index.
Experimental and numerical investigation on the suitability of semi-submersible floaters to support vertical axis wind turbine
Published in Ships and Offshore Structures, 2022
Experiments were carried in a wave flume of 90 m long, 4 m wide and 3 m deep with 2.5 m water depth at the Department of Ocean Engineering, Indian Institute of Technology Madras, India. The wave flume has a facility to generate two-dimensional long-crested regular and random waves using flap-type paddle. The plan and elevation view of the wave flume with the floater model positioned at 25 m away from the wave paddle is shown in Figure 2. The wave surface elevation was measured using a resistance-type wave probe. The wave probes were fixed to frame adjacent to the model, one on seaward side and second one on landward side to measure the wave heights before and after the wave crossed the model. The instruments were placed on the wind turbine base of the tower to measure the surge, heave and pitch motions. The surge and heave motions were measured using piezoelectric accelerometers having a sensitivity of 1000 mV/g. The roll and pitch angular motions were measured using dual axis inclinometers. These instruments were connected to a data acquisition system and a computer to record the measurements. The wind turbine working condition (operation) has been simulated by rotating the wind turbine at a rated speed of 78.11 rpm using a DC motor fitted at the bottom of the tower. Figure 3 shows the floater model with mooring line and instrumented setup installed in the wave flume.
Measurement of wave forces on a modelled ice floe by plastic plate under bichromatic waves
Published in Ships and Offshore Structures, 2023
Longwei Huang, Wenyue Lu, Jianmin Yang, Qing Dong
Figure 6 shows the mean horizontal force as a function of incident wave height. We defined the incident wave height in terms of the significant wave height (Hs) of the incident wave surface elevation given by Hs = 4σ, where σ is the standard deviation of the time series of the wave surface elevation. The peak wave force was derived from the maximum horizontal force of the recording time series.