In:
Transactions of the AIME, Society of Petroleum Engineers (SPE), Vol. 179, No. 01 ( 1949-12-1), p. 11-28
Abstract:
Generation of waves by storms, and the transformation of waves in shallowwater by local bottom topography are briefly reviewed. A detailed descriptionof water motion in waves explains the nature and distribution of wave forces. Anumerical example dealing with forces and moments against vertical pilessummarizes the principles involved. Introduction The oil industry is moving into the open waters of the Gulf of Mexico. Thedesign and construction of offshore drilling rigs present a number of difficultproblems, among them problems involving the action of waves on fixed andfloating structures. This paper deals with our present knowledge of ocean wavesas it pertains to these problems, and the principles involved in computing waveforces against fixed structures. It is hoped that the more difficult casepertaining to floating structures can be discussed at a later time. None of theengineering aspects of the problem are entered upon in this paper, yet anunderstanding of the principles presented here should be helpful in thesolution of practical problems. Nature of Wave Forces Waves are capable of exerting almost unbelievable forces. During a gale, waves at the harbor entrance of Amsterdam Canal in Holland lifted a 20-tonconcrete block, which was resting on the bottom in 12ft of water, and depositedit on top of a pier which was 5 ft above the high water mark. At WickBreakwater in Scotland, a mass of large stones in cement and bound togetherwith iron rods, weighing 1350 tons, was broken loose and moved bodily! But oneneed not go to Holland or Scotland to find evidence of damage that waves arecapable of inflicting (Fig I and 2). What is the mechanism by which waves are capable of exerting such enormousforces? To answer this, we must consider briefly the nature of wave motion.When a wind blows over a wheat field, waves appear to travel across the field, whereas the wheat itself remains rooted, slowly swinging back and forth.Similarly, in the case of water waves, the wave form travels swiftly over thewater surface, whereas the water particles oscillate back and forth, butscarcely advance. The speed of the wave form is called wave velocity, the speedof the water particles is called orbital velocity. This fundamental differencebetween wave velocity and orbital velocity was already recognized by Leonardoda Vinci. Orbital velocity is generally much slower than wave velocity exceptfor a breaking wave, a case which is of particular importance in theapplication to engineering problems. T.P. 2322
Type of Medium:
Online Resource
ISSN:
0081-1696
Language:
English
Publisher:
Society of Petroleum Engineers (SPE)
Publication Date:
1949
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