Print Email Facebook Twitter Application of the random storm method tot the air-gap problem Title Application of the random storm method tot the air-gap problem Author Heijermans, B.H. Contributor Battjes, J.A. (mentor) Holthuijsen, L.H. (mentor) Massie, W.W. (mentor) Tromans, P.S. (mentor) Faculty Civil Engineering and Geosciences Department Hydraulic Engineering Date 1991-05-01 Abstract This is a study of the statistics of the ocean surface. The extreme surface elevation arising from waves, tides and storm surge is calculated by a novel approach that appears to eliminate many of the shortcomings of the convential practice. The proposed method works with the statistics of storms rather than three hour periods. A storm may be regarded as a period (of order a day) of continuous severe seas. Successive storms can be treated as independent events. The new theory assumes that certain asymptotic properties of extreme values are applicable to storms. This allows us to treat extreme statistics within a storm in a straightforward way and to extrapolate to more severe storms (say 100 year level) from a short (eg. 25 year) data base. The method has been applied to hindcast data Erom NESS (Northern European Storm Study) for a location in the northern North Sea to predict extreme wave height. The largest storms from the north-west and the south-east quadrant were studied. From the time series of the significant wave height the probability distribution, P(H), oE the extreme wave height of each storm was calculated and, thereby, also the most probable extreme wave height of each storm. Comparisons of the various P(H) distributions showed that they can all be well represented by a one-parameter standard extreme value distribution in which the most probable extreme value appears as the parameter. Thus, if Hmp is given for a storm, the probability distribution of the largest wave is automatically known; it is p(H|Hmp). The H values Erom the 25 years of storms can be used to estimate a probability density function p(Hmp ) that allows us to extrapolate to 100 year conditions. In fact a novel asymptotic method was used to estimate the probability distribution of Hmp , p(Hmp ). Combination of p(Hmp ) and p(H|Hmp ) allows the calculation of the probability distribution of the Largest wave height for any random storm and, since the ave rage arrival rate of storms is known, for any desired return period. The 100 year wave height obtained in this way is 26.4 metres. A conventional analysis of the same data would give a value of order of 28 metres, including short term variability. The method is not only applicable to wave height but also to surface elevation. Exactly the same procedure is followed except that wave height is replaced by surface elevation induced by waves, storm surge and tide. This method is applied to check the air-gap of existing structures to help to decide whether the existing platforms some settiement of the structures occurs. Subject ocean surfacewavesstormsextreme statisticswave heightair-gap To reference this document use: http://resolver.tudelft.nl/uuid:bdf242b3-854c-4cf7-bb00-e715fb31129f Part of collection Student theses Document type master thesis Rights (c) 1991 Heijermans, B.H. Files PDF Heijermans1991a.pdf 23.83 MB Close viewer /islandora/object/uuid:bdf242b3-854c-4cf7-bb00-e715fb31129f/datastream/OBJ/view