Loading due to interaction of waves with colinear and oblique currents

A study on the loading of an oblique surface wave and a surface current field on a fixed vertical slender cylinder in a 3D flow frame is illustrated in the present paper. The three dimensional expressions describing the characteristics of the combined wave-current field in terms of mass, momentum and energy flux conservation equations are formulated. The parameters before the interaction of the oblique wave-free uniform current and current-free wave are used to formulate the kinematics of the flow field. These expressions are also employed to formulate and calculate the loads imparted by the wave-current combined flow on a bottom mounted slender vertical cylinder. In the present study two different situations are assumed where current is uniform over depth and also acting over a layer of fluid that extends from the free surface to a specified finite depth. In this paper we extend the approach considered in Zaman and Baddour (2004) for the wave-current analysis. Morison et al. (1950) equation is deployed for the load computations in all cases. The above models are utilized to compute the loads and moments on a slender cylinder for a wave with varying range of incidence current field.Peer reviewed: YesNRC publication: Ye

Transformation of mono- and multi-chromatic water waves propagating from a Quasi-deepwater to a shallow water region.

A vertically integrated 3D numerical model that uses the concept of depth average velocity distribution with enhanced dispersion characteristics investigates the propagation and transformation of mono- and multi-chromatic waves from a quasi-deep region to shallow water region. A finite difference method has been employed for the numerical computation that follows ADI (Alternating Direction Implicit) algorithm. The local sea bottom is uneven and turns into a moderately shallow water due to presence of a ridge-like bottom near the coast. The bottom configuration is from a location off Nova Scotia coast in Canada. Detail results and discussions are presented.Peer reviewed: NoNRC publication: Ye

OMAE2009-80104 TRANSFORMATION OF MONO-AND MULTI-CHROMATIC WATER WAVES PROPAGATING FROM A QUASI-DEEPWATER TO A SHALLOW WATER REGION

ABSTRACT A vertically integrated 3D numerical model that uses the concept of depth average velocity distribution with enhanced dispersion characteristics investigates the propagation and transformation of mono-and multi-chromatic waves from a quasi-deep region to shallow water region. A finite difference method has been employed for the numerical computation that follows ADI (Alternating Direction Implicit) algorithm. The local sea bottom is uneven and turns into a moderately shallow water due to presence of a ridge-like bottom near the coast. The bottom configuration is from a location off Nova Scotia coast in Canada. Detail results and discussions are presented

Shallow Water Wave Correction in the OEB (Monochromatic and Bichromatic Waves)

In this work first order and second order wave generation techniques are utilized to study the correct generation of mono and bichromatic waves in the OEB. For a flat bottom wave basin when the interaction between two frequencies are considered bounded sub harmonics or bounded low frequency waves are generated at the difference frequency and bounded super harmonics or bounded high frequency waves are generated at the sum frequency and they travel locked with their generating / fundamental wave components along with some unwanted free waves. These free waves are, free waves due to first order motion of the wave boards, free wave due to displacement of the wave board from its zero position and free wave due to local disturbances. These unwanted free waves are inevitable due to the linear motion of the wave maker. The second order wave generation technique includes second order board motion and correction components of the above-mentioned unwanted free waves. In this study only sub-harmonics or low frequency wave components are considered. Total 14 wave probes are used to capture the data in the wave tank. A NRC-IOT code (LWAVE) is used to isolate the primary waves, the bounded waves and the unwanted free waves from the measured data at each wave probe. The measured data are analyzed in this paper to illustrate the differences in the waves generated by two different generation techniques.Peer reviewed: NoNRC publication: Ye

Wave propagation before and after the floor work in the OEB in 2010

Recently the south-west side trenches under and in front of the wave makers in the OEB have been permanently filled-up to provide a homogeneous bottom and uniform water depth all over the basin. This work is to understand the improvement of the wave quality after the floor work. Two sets of experimental data comprised of mono- and bi-chromatic waves before and after the floor work are compared to identify the impact of the development work on the wave generation and propagation in the OEB. Results are compared between the measured wave data, before and after the floor work in the OEB. Results are shown in terms of surface elevations and wave energies propagations for measured waves, primary waves, bounded waves and unwanted second order free waves. In most of the cases it is observed from the results that the shallower the wave the better the wave quality after the floor work.Peer reviewed: YesNRC publication: Ye

Shallow water wave correction in the OEB (multichromatic waves)

Accurate generation of the primary waves and the reproduction of the group-induced second-order low and high frequency waves have been considered essential for physical model test in the laboratory. In the laboratory when multi-chromatic primary waves are generated the required bounded waves will be generated naturally at the difference frequencies. In addition to that several unwanted free waves are also generated. The free waves, having the same frequencies of the bounded waves are reproduced due to mismatch of the boundary conditions at the wave paddle. The other two types of free waves are due to the wave paddle displacement and the local disturbances. We carried out physical experiments to identify the second order spurious waves in shallow water in the Offshore Engineering Basin (OEB) at the Institute for Ocean Technology (IOT) of National Research Council (NRC) Canada. In the basin water depths in the range of 0.4m to 0.6m are used for the experiments. The peak wave periods also have varied from 1.133s to 2.145s. In this experiment JONSWAP and TMA spectrums are separately used. The drive signals of the wave-makers are generated using first-order and second-order wave generation techniques. Total 14 wave probes are used to capture the data in the wave tank. A NRC-IOT code (LWAVE) is used to isolate the primary waves, the bounded waves and the unwanted free waves from the measured data at each wave probe. The measured data are analyzed in this paper to illustrate the differences in the waves generated by two different generation techniques.Peer reviewed: YesNRC publication: Ye