Wave Forecasting in Shallow Water: A New Set of Growth Curves Depending on Bed Roughness

Forecasting relationships have been recognized as an important tool to be applied together, or not, with complete numerical modelling in order to reconstruct the wave field in coastal areas properly when the available wave data is limited. In recent years, the literature has offered several comprehensive sets of field experiments investigating the form of the asymptotic, depth-limited wind waves. This has made it possible to reformulate the original deep water equations, taking into account the effects of water depth, if wind waves are locally generated in shallow and confined basins. The present paper is an initial attempt to further contribute to the shallow water forecasting curves which are currently available, also considering the role on the wave generation of a variable equivalent bottom roughness. This can offer the possibility of applying shallow growth curves to a broad variety of contexts, for which bed composition and forms can be different. Simple numerical tests have been conducted to reproduce the fully developed conditions of wave motion with variable roughness values. To validate the new set of equations, they have been applied to a real shallow lake for which both experimental and numerical wave data is available. The comparison of the obtained results is very encouraging in proceeding with this approach.

Download Full-text

REVISIONS IN WAVE FORECASTING: DEEP AND SHALLOW WATER

Coastal Engineering Proceedings ◽

10.9753/icce.v6.3 ◽

2011 ◽

Vol 1 (6) ◽

pp. 3 ◽

Cited By ~ 6

Author(s):

C. L. Bretschneider

Keyword(s):

Shallow Water ◽

Meteorological Data ◽

Wind Waves ◽

Atmospheric Stability ◽

Slight Modification ◽

Practical Method ◽

Distribution Functions ◽

Point Of View ◽

Area Of Interest ◽

Wave Forecasting

During the past six years since the latest revisions in wave forecasting (Bretschneider 1951) were made, much information has become available such that another revision is in order. An abundance of published (and unpublished) accounts of wave generation and decay in both deep and shallow water from various sources, as well as new ideas in the art of wave forecasting, are used in this revision. Deep water wave forecasting relationships, relationships for the generation of wind waves in shallow water of constant depth, and techniques for forecasting wind waves over the Continental Shelf are included in this paper. Forecasting hurricane waves is also discussed, from the engineering design point of view. The concept of significant wave is still retained as the most practical method in wave forecasting to date. The significant period has definite significance in that the wave energy is propagated forward at a speed approximately equal to the corresponding group velocity. The graphical approach (Wilson 1955) for moving fetches and variable wind vectors is discussed, and is the best approach for forecasting waves. Without Wilson’s graphical technique it is difficult for any two forecasters supplied with the same meteorological data to obtain the same degree of verification, or determine whether the forecaster or the forecasting relationships are in error. It is quite possible that by use of this technique further revisions in wave forecasting are possible. The problem of wave variability is discussed, and the distribution functions are given. A short summary of the wave spectra (Bretschneider 1958) used in connection with the revisions is also given. When the present forecasting relationships are applied to sections of the world, other than that from which the basic data were procured, it is recommended that atmospheric stability factors be taken into account. This essentially involves a slight modification or calibration of the forecasting relationships and techniques, prior to general use in the area of interest.

Download Full-text

Numerical Calculation of Wind Waves in Shallow Water

Coastal Engineering 1966 ◽

10.1061/9780872620087.004 ◽

1967 ◽

Cited By ~ 3

Author(s):

Takeshi Ijima ◽

Frederick L. W. Tang

Keyword(s):

Numerical Calculation ◽

Shallow Water ◽

Wind Waves

Download Full-text

Visual Navigation for Recovering an AUV by Another AUV in Shallow Water

Sensors ◽

10.3390/s19081889 ◽

2019 ◽

Vol 19 (8) ◽

pp. 1889 ◽

Cited By ~ 4

Author(s):

Shuang Liu ◽

Hongli Xu ◽

Yang Lin ◽

Lei Gao

Keyword(s):

Shallow Water ◽

Pose Estimation ◽

Field Experiments ◽

State Of The Art ◽

Autonomous Underwater Vehicles ◽

Visual Navigation ◽

Ambient Light ◽

Robust Detection ◽

Novel Method ◽

Coarse To Fine

Autonomous underwater vehicles (AUVs) play very important roles in underwater missions. However, the reliability of the automated recovery of AUVs has still not been well addressed. We propose a vision-based framework for automatically recovering an AUV by another AUV in shallow water. The proposed framework contains a detection phase for the robust detection of underwater landmarks mounted on the docking station in shallow water and a pose-estimation phase for estimating the pose between AUVs and underwater landmarks. We propose a Laplacian-of-Gaussian-based coarse-to-fine blockwise (LCB) method for the detection of underwater landmarks to overcome ambient light and nonuniform spreading, which are the two main problems in shallow water. We propose a novel method for pose estimation in practical cases where landmarks are broken or covered by biofouling. In the experiments, we show that our proposed LCB method outperforms the state-of-the-art method in terms of remote landmark detection. We then combine our proposed vision-based framework with acoustic sensors in field experiments to demonstrate its effectiveness in the automated recovery of AUVs.

Download Full-text

Investigation of Directional Spreading of Waves in Relatively Shallow Water

Volume 1: Offshore Technology; Special Symposium on Ocean Measurements and Their Influence on Design ◽

10.1115/omae2007-29589 ◽

2007 ◽

Author(s):

Vale´ria S. Rego

Keyword(s):

South America ◽

Shallow Water ◽

Atlantic Coast ◽

Spreading Factor ◽

Wave Kinematics ◽

Wave Data ◽

Practical Design ◽

Particle Velocities

The directional spreading of waves is investigated for relatively shallow water (20m depth) wave data, collected with acoustic current profilers, along the Atlantic Coast of South America. Values for the wave kinematics or wave spreading factor, recommended by API and ISO for reduction of in-line particle velocities and accelerations under waves due to directional spreading, are calculated in order to allow judgement of approximate values that can be used in shallow water regions for practical design applications.

Download Full-text

Random wave-driven drag forces on near-bed vegetation in shallow water based on deepwater wind conditions

Proceedings of the Institution of Mechanical Engineers Part M Journal of Engineering for the Maritime Environment ◽

10.1177/1475090218825377 ◽

2019 ◽

Vol 233 (4) ◽

pp. 1287-1290

Author(s):

Dag Myrhaug

Keyword(s):

Shallow Water ◽

Drag Force ◽

Wind Waves ◽

Wave Spectrum ◽

Random Wave ◽

Random Waves ◽

Coastal Zones ◽

Drag Forces ◽

Mean Wind Speed ◽

Wave Induced

This article provides a simple analytical method for giving estimates of random wave-driven drag forces on near-bed vegetation in shallow water from deepwater wind conditions. Results are exemplified using a Pierson–Moskowitz model wave spectrum for wind waves with the mean wind speed at the 10 m elevation above the sea surface as the parameter. The significant value of the drag force within a sea state of random waves is given, and an example typical for field conditions is presented. This method should serve as a useful tool for assessing random wave-induced drag force on vegetation in coastal zones and estuaries based on input from deepwater wind conditions.

Download Full-text

On Evolution of Young Wind Waves in Time and Space

Atmosphere ◽

10.3390/atmos10090562 ◽

2019 ◽

Vol 10 (9) ◽

pp. 562 ◽

Cited By ~ 1

Author(s):

Shemer

Keyword(s):

Wave Field ◽

Field Experiments ◽

Wind Wave ◽

Wind Waves ◽

Wave Generation ◽

Wind Forcing ◽

Spatial And Temporal Variation ◽

Extensive Discussion ◽

Deterministic Theory ◽

Theoretical Approaches

The mechanisms governing the evolution of the wind-wave field in time and in space are not yet fully understood. Various theoretical approaches have been offered to model wind-wave generation. To examine their validity, detailed and accurate experiments under controlled conditions have to be carried out. Since it is next to impossible to get the required control of the governing parameters and to accumulate detailed data in field experiments, laboratory studies are needed. Extensive previously unavailable results on the spatial and temporal variation of wind waves accumulated in our laboratory under a variety of wind-forcing conditions and using diverse measuring techniques are reviewed. The spatial characteristics of the wind-wave field were determined using stereo video imaging. The turbulent airflow above wind waves was investigated using an X-hot film. The wave field under steady wind forcing as well as evolving from rest under impulsive loading was studied. An extensive discussion of the various aspects of wind waves is presented from a single consistent viewpoint. The advantages of the stochastic approach suggested by Phillips over the deterministic theory of wind-wave generation introduced by Miles are demonstrated. Essential differences between the spatial and the temporal analyses of wind waves’ evolution are discussed, leading to examination of the applicability of possible approaches to wind-wave modeling.

Download Full-text