Statistical properties of winds near the Taichung Harbour are investigated. The 26 years'incomplete data of wind speeds, measured on an hourly basis, are used as reference. The possibility of imputation using simu...Statistical properties of winds near the Taichung Harbour are investigated. The 26 years'incomplete data of wind speeds, measured on an hourly basis, are used as reference. The possibility of imputation using simulated results of the Auto-Regressive (AR), Moving-Average (MA), and/ or Auto-Regressive and Moving-Average (ARMA) models is studied. Predictions of the 25-year extreme wind speeds based upon the augmented data are compared with the original series. Based upon the results, predictions of the 50- and 100-year extreme wind speeds are then made.展开更多
Reflection and transmission of random waves from submerged ohstacles under various conditions are investigated in this study by means of the boundary element method. The algorithm is based on the Lagrangian descriptio...Reflection and transmission of random waves from submerged ohstacles under various conditions are investigated in this study by means of the boundary element method. The algorithm is based on the Lagrangian description with finite difference adopted for the approximation of time derivative. The accuracy of the model is confirmed by a previous study of the transmission of irregular waves in a water tank without any obstacle, under which sets of submerged breakwaters are located. To reduce the effect of reflection from the wall, a sponge zone is employed at the other end of the flume as an artificial absorbing beach. The power spectrum of Bretschneider-Mitsuyasu type defined by significant wave height, H1/3, and period, T1/3, is employed for the condition of incident waves chosen for the generation of irregular waves. Time histofies of water elevations are measured with numerous pseudo wave gages on the free water surface. With reference to the method for the estimation of irregular incident and reflected waves in random sea presented by Goda and Suzuki （1976）, the dissipation efficiency of the breakwaters is investigated. Gauges in different positions are tested for their suitability for the estimation of reflection coefficients for irregular waves. The present results demonstrate the effectiveness of the estimation of reflection coefficient for random waves, and indicate the feasibility of the numerical model.展开更多
Distribution of wave heights and surface elevations of wind-driven waves are studied. Records of surface elevations obtained from both field observations and laboratory measurements are analyzed. Wave heights can be a...Distribution of wave heights and surface elevations of wind-driven waves are studied. Records of surface elevations obtained from both field observations and laboratory measurements are analyzed. Wave heights can be approximated by normal, two-parameter Weibull, and/or Rayleigh distribution. However, while the first two models may have almost equal probabilities to fit measured data quite satisfactorily, the Rayleigh distribution does not appear to be a good model for the majority of the cases studied. Surface elevations from field data are well described by the Gaussian model, but as with increasing wind speeds, water surface in a wind-wave flume deviates from normality, and the Edgeworth/s form of the type A Gram-Charlier series is then applied.展开更多
A numerical wave tank with passive absorption for irregular waves is considered in this paper. Waves with spectral shapes corresponding to that of the Mitsuyasu- Bretschneider type are used as the initial condition at...A numerical wave tank with passive absorption for irregular waves is considered in this paper. Waves with spectral shapes corresponding to that of the Mitsuyasu- Bretschneider type are used as the initial condition at one end of the flume, An absorbing boundary is imposed at the other end of the wave flume to minimize reflection. By use of a Lagrangian description for the Surface elevation, and finite difference for approximation of the time derivative, the problem is then solved by the boundary element method, The effects of the absorbing boundary are investigated by varying the values of the absorption coefficient mu, and studying the time histories of the Surface elevations 'recorded' on pre-selected locations.展开更多
基金The project is partly supported by the National Science Council, Contract Nos. NSC-89-261 l-E-019-024 (JZY), and NSC-89-2611-E-019-027 (CRC).
文摘Statistical properties of winds near the Taichung Harbour are investigated. The 26 years'incomplete data of wind speeds, measured on an hourly basis, are used as reference. The possibility of imputation using simulated results of the Auto-Regressive (AR), Moving-Average (MA), and/ or Auto-Regressive and Moving-Average (ARMA) models is studied. Predictions of the 25-year extreme wind speeds based upon the augmented data are compared with the original series. Based upon the results, predictions of the 50- and 100-year extreme wind speeds are then made.
文摘Reflection and transmission of random waves from submerged ohstacles under various conditions are investigated in this study by means of the boundary element method. The algorithm is based on the Lagrangian description with finite difference adopted for the approximation of time derivative. The accuracy of the model is confirmed by a previous study of the transmission of irregular waves in a water tank without any obstacle, under which sets of submerged breakwaters are located. To reduce the effect of reflection from the wall, a sponge zone is employed at the other end of the flume as an artificial absorbing beach. The power spectrum of Bretschneider-Mitsuyasu type defined by significant wave height, H1/3, and period, T1/3, is employed for the condition of incident waves chosen for the generation of irregular waves. Time histofies of water elevations are measured with numerous pseudo wave gages on the free water surface. With reference to the method for the estimation of irregular incident and reflected waves in random sea presented by Goda and Suzuki （1976）, the dissipation efficiency of the breakwaters is investigated. Gauges in different positions are tested for their suitability for the estimation of reflection coefficients for irregular waves. The present results demonstrate the effectiveness of the estimation of reflection coefficient for random waves, and indicate the feasibility of the numerical model.
文摘Distribution of wave heights and surface elevations of wind-driven waves are studied. Records of surface elevations obtained from both field observations and laboratory measurements are analyzed. Wave heights can be approximated by normal, two-parameter Weibull, and/or Rayleigh distribution. However, while the first two models may have almost equal probabilities to fit measured data quite satisfactorily, the Rayleigh distribution does not appear to be a good model for the majority of the cases studied. Surface elevations from field data are well described by the Gaussian model, but as with increasing wind speeds, water surface in a wind-wave flume deviates from normality, and the Edgeworth/s form of the type A Gram-Charlier series is then applied.
基金The authors wish to express their gratitude for the financial aid of the National Science Council, China.Project Nos. NSC-89-2611-E-019-027(CRC)and NSC-89-2611-E-019-058(JZY).
文摘A numerical wave tank with passive absorption for irregular waves is considered in this paper. Waves with spectral shapes corresponding to that of the Mitsuyasu- Bretschneider type are used as the initial condition at one end of the flume, An absorbing boundary is imposed at the other end of the wave flume to minimize reflection. By use of a Lagrangian description for the Surface elevation, and finite difference for approximation of the time derivative, the problem is then solved by the boundary element method, The effects of the absorbing boundary are investigated by varying the values of the absorption coefficient mu, and studying the time histories of the Surface elevations 'recorded' on pre-selected locations.
