Methods of creating a complex seaway in a model basin
Date
1958-09
Authors
Glover, Robert E. (Robert Ellsworth), 1896-1984, author
Civil Engineering Section, Colorado State University, publisher
Journal Title
Journal ISSN
Volume Title
Abstract
The wave patterns due to long wave generators, which produce displacements uniformly distributed along their length, are first investigated. Formulas are developed by which the diffraction pattern produced by single sources or long wave generators can be estimated. Approximations have been made when simplified computation procedures could be obtained thereby. These methods are then used to investigate the types of short crested seas, which could be produced in circular or rectangular model basins by a limited number of wave generators. It is found that short crested seas can be produced in this way but that there is difficulty in obtaining uniform conditions over a wide test area. A servomotor type of wave generator whose performance can be controlled by a cam is described. Such a wave generator has advantages when used for producing irregular types of waves. The requirements, which must be met if a replica of an actual storm sea is to be reproduced over the entire area of a model basin and sustained for a period of time ample for testing purposes, are next investigated. This investigation makes use of the mathematical developments, which are concerned with the conditions of uniqueness for solutions of the differential equation of Laplace. It is concluded that the replica sea can be realized if the observed undulations are reproduced, to model scale, completely around the perimeter of the model basin and the driving forces of wind are supplied. Since none of the conventional types of wave generators would be satisfactory for this service, because of the waves corning in to their location from other generators, a new type of wave generator is devised. This generator embodies the elements described previously but its action is now controlled by a device which senses the wave height at its location, compares it with a program, and acts to bring the actual wave height to the programmed wave height. The number of wave generators required for production of the replica sea is investigated. With a finite number of wave generators, a true replica sea can only be approximated but the approximation grows better as the lengths of the wave generators is shortened and their number correspondingly increased. In any case, the length of each single wave generator must be short compared to the length of the model to be tested. The requirements, which must be met if wave generators of the new type are to function properly, are studied analytically. Because of the stringency of these requirements, it is considered advisable to build and test a pair of them before any large-scale installation is attempted.
Description
CER58REG43.
September 1958.
Includes bibliographical references (pages 96-99).
September 1958.
Includes bibliographical references (pages 96-99).
Rights Access
Subject
Ocean waves -- Mathematical models