In this paper, we propose a new method to estimate the wave height of a specifi c return period based on the Hurst rule and a self-affi ne fractal formula. A detailed description of our proposed model is presented in ...In this paper, we propose a new method to estimate the wave height of a specifi c return period based on the Hurst rule and a self-affi ne fractal formula. A detailed description of our proposed model is presented in this paper. We use the proposed model to analyze wave height data recorded along the coast of Chaolian Island from 1963 to 1989. The results show that the performance of our proposed model in estimating design wave heights is superior to traditional models.展开更多
The paper introduces a new approach to estimating the T-year return-period wave height (TRPW), i.e. the wave height expected to occur in T-year, from two sets of observed extreme data and on the basis of the maximum e...The paper introduces a new approach to estimating the T-year return-period wave height (TRPW), i.e. the wave height expected to occur in T-year, from two sets of observed extreme data and on the basis of the maximum entropy principle. The main points of the approach are as follows. 1) A maximum entropy probability density function (PDF) for the extreme wave height H is derived from a Euler equation subject to some necessary and rational constraints. 2) The parameters in the function are expressed in terms of the mth moment of H. 3) This PDF is convenient to theoretical and practical applications as it is simple and its four parameters are easy to be determined from observed extreme data. An example is given for estimating the TRPW in 50 and 100 years by the present approach and by some currently used methods using observed data at two hydrographic stations.The comparison of the estimated results shows that the present approach is quite similar to the Pearson-Ⅲ and Gumbel methods.展开更多
Return periods calculated for different environmental conditions are key parameters for ocean platform design.Many codes for offshore structure design give no consideration about the correlativity among multi-loads an...Return periods calculated for different environmental conditions are key parameters for ocean platform design.Many codes for offshore structure design give no consideration about the correlativity among multi-loads and over-estimate design values.This frequently leads to not only higher investment but also distortion of structural reliability analysis.The definition of design return period in existing codes and industry criteria in China are summarized.Then joint return periods of different ocean environmental parameters are determined from the view of service term and danger risk.Based on a bivariate equivalent maximum entropy distribution,joint design parameters are estimated for the concomitant wave height and wind speed at a site in the Bohai Sea.The calculated results show that even if the return period of each environmental factor,such as wave height or wind speed,is small,their combinations can lead to larger joint return periods.Proper design criteria for joint return period associated with concomitant environmental conditions will reduce structural size and lead to lower investment of ocean platforms for the exploitation of marginal oil field.展开更多
A new compound distribution model for extreme wave heights of typhoon-affected sea areas is proposed on the basis of the maximum-entropy principle. The new model is formed by nesting a discrete distribution in a conti...A new compound distribution model for extreme wave heights of typhoon-affected sea areas is proposed on the basis of the maximum-entropy principle. The new model is formed by nesting a discrete distribution in a continuous one, having eight parameters which can be determined in terms of observed data of typhoon occurrence-frequency and extreme wave heights by numerically solving two sets of equations derived in this paper. The model is examined by using it to predict the N-year return-period wave height at two hydrology stations in the Yellow Sea, and the predicted results are compared with those predicted by use of some other compound distribution models. Examinations and comparisons show that the model has some advantages for predicting the N-year return-period wave height in typhoon-affected sea areas.展开更多
Based on historical wind fields in the Bohai Sea, a sequence of annual extremal wave heights is produced with numerical wave models for deep-water and shallow water. The design wave heights with different return perio...Based on historical wind fields in the Bohai Sea, a sequence of annual extremal wave heights is produced with numerical wave models for deep-water and shallow water. The design wave heights with different return periods for the nearest deep-water point and for the shallow water point are estimated on the basis of P-III type, Weibull distribution, and Gumbel distribution; and the corresponding values for the shallow water point are also estimated based on the HISWA model with the input of design wave heights for the nearest deep-water point. Comparisons between design wave heights for the shallow water point estimated on the basis of both distribution functions are HISWA model show that the results from different distribution functions scatter considerably, and influenced strongly by return periods; however, the results from the HISWA model are convergent, that is, the influence of the design wave heights estimated with different distribution functions for deep water is weakened, and the estimated values decrease for long return periods and increase for short return periods. Therefore, the numerical wave model gives a more stable result in shallow water design wave estimation because of the consideration of the effect of physical processes which occur in shallow water.展开更多
随着西非海洋经济与港口建设的不断发展,对西非海域水动力特征,特别是波浪要素时空分布特征的认识显得愈加重要。基于欧洲中期天气预报中心(ECWMF) ERA-5再分析数据集中的42 a (1979-2020年)逐时波要素数据,对西非区域的混合浪、涌浪和...随着西非海洋经济与港口建设的不断发展,对西非海域水动力特征,特别是波浪要素时空分布特征的认识显得愈加重要。基于欧洲中期天气预报中心(ECWMF) ERA-5再分析数据集中的42 a (1979-2020年)逐时波要素数据,对西非区域的混合浪、涌浪和风浪的有效波高和周期的时空分布进行分析。该海域旱季和雨季的波要素特征具有显著区别。在空间分布上,西非海域的涌浪、混合浪有效波高由近岸向离岸处、低纬度向高纬度不断增大;混合浪以及涌浪的周期由中部区域向四周不断增大;风浪波高和周期在赤道以北,由南向北逐渐增大;赤道以南,由南向北先增大后减小。涌浪和混合浪的月度分布主要呈现3种特征,分别为月度变化较小的无峰值型以及月度变化明显的Ω形和倒Ω形。此外,通过波浪危险性分析,发现其危险性从西非海域中部近岸区域向离岸、从低纬度向高纬度逐渐增加,其中西非南部海域的危险性最高,佛得角北部海域的危险性次之。展开更多
基金Supported by the National Natural Science Foundation of China’s“Study on Multi-objective Four-layer Nested Probability Model(MOFLNPM)and its Application to Risk Assessment for Coastal Engineering”(No.51379195)the Shandong Province Natural Science“Study on the Risk Assessments and Statistical Analysis of Marine Engineering based on Multi-target Three-level Nested Statistical Model”(No.ZR2013EEM034)+1 种基金the National Natural Science Foundation of China(No.41476078)the Science Research Program of Zhejiang Province(No.2015C34013)
文摘In this paper, we propose a new method to estimate the wave height of a specifi c return period based on the Hurst rule and a self-affi ne fractal formula. A detailed description of our proposed model is presented in this paper. We use the proposed model to analyze wave height data recorded along the coast of Chaolian Island from 1963 to 1989. The results show that the performance of our proposed model in estimating design wave heights is superior to traditional models.
基金the Natural Science Foundation of China under Contract No.40706012the Young Scientist Foundation of State Oceanic Administration under Contract No.2008209+1 种基金the Basic Science Operational Fund of the Ministry of Finance assigned to the Third Institute of Oceanography,State Oceanic Administration under Contract No.2007010‘863’program No.2006AA09A301
文摘The paper introduces a new approach to estimating the T-year return-period wave height (TRPW), i.e. the wave height expected to occur in T-year, from two sets of observed extreme data and on the basis of the maximum entropy principle. The main points of the approach are as follows. 1) A maximum entropy probability density function (PDF) for the extreme wave height H is derived from a Euler equation subject to some necessary and rational constraints. 2) The parameters in the function are expressed in terms of the mth moment of H. 3) This PDF is convenient to theoretical and practical applications as it is simple and its four parameters are easy to be determined from observed extreme data. An example is given for estimating the TRPW in 50 and 100 years by the present approach and by some currently used methods using observed data at two hydrographic stations.The comparison of the estimated results shows that the present approach is quite similar to the Pearson-Ⅲ and Gumbel methods.
基金supported by the National Natural Science Foundation of China (51279186)the National Program on Key Basic Research Project (2011CB013704)
文摘Return periods calculated for different environmental conditions are key parameters for ocean platform design.Many codes for offshore structure design give no consideration about the correlativity among multi-loads and over-estimate design values.This frequently leads to not only higher investment but also distortion of structural reliability analysis.The definition of design return period in existing codes and industry criteria in China are summarized.Then joint return periods of different ocean environmental parameters are determined from the view of service term and danger risk.Based on a bivariate equivalent maximum entropy distribution,joint design parameters are estimated for the concomitant wave height and wind speed at a site in the Bohai Sea.The calculated results show that even if the return period of each environmental factor,such as wave height or wind speed,is small,their combinations can lead to larger joint return periods.Proper design criteria for joint return period associated with concomitant environmental conditions will reduce structural size and lead to lower investment of ocean platforms for the exploitation of marginal oil field.
基金supported by the Open Fund of the Key Laboratory of Research on Marine Hazards Forecasting (Grant No.LOMF1101)the Shanghai Typhoon Research Fund (Grant No. 2009ST05)the National Natural Science Foundation of China(Grant No. 40776006)
文摘A new compound distribution model for extreme wave heights of typhoon-affected sea areas is proposed on the basis of the maximum-entropy principle. The new model is formed by nesting a discrete distribution in a continuous one, having eight parameters which can be determined in terms of observed data of typhoon occurrence-frequency and extreme wave heights by numerically solving two sets of equations derived in this paper. The model is examined by using it to predict the N-year return-period wave height at two hydrology stations in the Yellow Sea, and the predicted results are compared with those predicted by use of some other compound distribution models. Examinations and comparisons show that the model has some advantages for predicting the N-year return-period wave height in typhoon-affected sea areas.
基金This work was financially supported by the National Natural Science Foundation of China(Grant No.49776282)
文摘Based on historical wind fields in the Bohai Sea, a sequence of annual extremal wave heights is produced with numerical wave models for deep-water and shallow water. The design wave heights with different return periods for the nearest deep-water point and for the shallow water point are estimated on the basis of P-III type, Weibull distribution, and Gumbel distribution; and the corresponding values for the shallow water point are also estimated based on the HISWA model with the input of design wave heights for the nearest deep-water point. Comparisons between design wave heights for the shallow water point estimated on the basis of both distribution functions are HISWA model show that the results from different distribution functions scatter considerably, and influenced strongly by return periods; however, the results from the HISWA model are convergent, that is, the influence of the design wave heights estimated with different distribution functions for deep water is weakened, and the estimated values decrease for long return periods and increase for short return periods. Therefore, the numerical wave model gives a more stable result in shallow water design wave estimation because of the consideration of the effect of physical processes which occur in shallow water.
文摘随着西非海洋经济与港口建设的不断发展,对西非海域水动力特征,特别是波浪要素时空分布特征的认识显得愈加重要。基于欧洲中期天气预报中心(ECWMF) ERA-5再分析数据集中的42 a (1979-2020年)逐时波要素数据,对西非区域的混合浪、涌浪和风浪的有效波高和周期的时空分布进行分析。该海域旱季和雨季的波要素特征具有显著区别。在空间分布上,西非海域的涌浪、混合浪有效波高由近岸向离岸处、低纬度向高纬度不断增大;混合浪以及涌浪的周期由中部区域向四周不断增大;风浪波高和周期在赤道以北,由南向北逐渐增大;赤道以南,由南向北先增大后减小。涌浪和混合浪的月度分布主要呈现3种特征,分别为月度变化较小的无峰值型以及月度变化明显的Ω形和倒Ω形。此外,通过波浪危险性分析,发现其危险性从西非海域中部近岸区域向离岸、从低纬度向高纬度逐渐增加,其中西非南部海域的危险性最高,佛得角北部海域的危险性次之。
