50-year environmental contour plot according to IEC 61400-3 standards, but including specific tail fitting. 

Contexts in source publication

Context 1

... s s , lim In this particular case, we made distinction between the point-in-time distribution, that represents the probabilistic behavior of all data range but the right tail, and the extreme-value distribution, that characterizes the right tail above the selected threshold. Note that the point-in-time distributions F V PT and F H PT s | V correspond, respectively, to F V ( v ) and F H s | V ( H s ) from expression (4). The new 50-year environmental contour for a 1-hour sea state duration improving the probability density functions at the right tails is shown in Figure 7. The improvement in the region of interest, i.e. the one associated with high values of the significant wave height and wind speeds in the range corresponding to power production, is significant. Note that with previous approach significant wave heights related to the 50-year environmental contour for low wind speed values are above 10 meters, even higher than those related to high wind speeds, which is physically unlikely. The IEC 61400-3 standards also recommend to use for all wind speeds of the unconditional extreme significant wave height with a recurrence period of 50 years as a conservative value for H s . Note that according to the fitting shown in Figure 8, this conservative value is equal to 9 . 6483 m (white circle marker spec- ifier). Since this value is above the 50-year environmental contour (see Figure 7), it is the one designer must take if the second analysis is performed. In contrast, in case using the first analysis, designer would use significant wave heights considerable above this threshold for low wind speeds, leading to an exces- sive conservationist. These results clearly demonstrated the importance of considering both the point-in-time and right-tail distributions. It is important to clarify that in both cases, the left tail of the distributions is reproduced inappro- priately. Contour plot intercepts negative wind speed and significant wave height values, which is impossi- ble. However, this does not distort the relevant results from the engineering perspective, i.e. those in the upper tail. Alternatively, an specific distribution for the left tail could be used ...

Context 2

... s s , lim In this particular case, we made distinction between the point-in-time distribution, that represents the probabilistic behavior of all data range but the right tail, and the extreme-value distribution, that characterizes the right tail above the selected threshold. Note that the point-in-time distributions F V PT and F H PT s | V correspond, respectively, to F V ( v ) and F H s | V ( H s ) from expression (4). The new 50-year environmental contour for a 1-hour sea state duration improving the probability density functions at the right tails is shown in Figure 7. The improvement in the region of interest, i.e. the one associated with high values of the significant wave height and wind speeds in the range corresponding to power production, is significant. Note that with previous approach significant wave heights related to the 50-year environmental contour for low wind speed values are above 10 meters, even higher than those related to high wind speeds, which is physically unlikely. The IEC 61400-3 standards also recommend to use for all wind speeds of the unconditional extreme significant wave height with a recurrence period of 50 years as a conservative value for H s . Note that according to the fitting shown in Figure 8, this conservative value is equal to 9 . 6483 m (white circle marker spec- ifier). Since this value is above the 50-year environmental contour (see Figure 7), it is the one designer must take if the second analysis is performed. In contrast, in case using the first analysis, designer would use significant wave heights considerable above this threshold for low wind speeds, leading to an exces- sive conservationist. These results clearly demonstrated the importance of considering both the point-in-time and right-tail distributions. It is important to clarify that in both cases, the left tail of the distributions is reproduced inappro- priately. Contour plot intercepts negative wind speed and significant wave height values, which is impossi- ble. However, this does not distort the relevant results from the engineering perspective, i.e. those in the upper tail. Alternatively, an specific distribution for the left tail could be used ...