02 September RP-C Environmental Conditions and Environmental Loads n RP-C is an updated and enhanced version of DNV. Find the most up-to-date version of DNVGL-RP-C at Engineering DNV RP C Environmental Conditions and Environmental Loads_ – DNV推荐做法,适用各种浮式结构环境载荷的计算.
|Published (Last):||27 September 2015|
|PDF File Size:||4.24 Mb|
|ePub File Size:||8.26 Mb|
|Price:||Free* [*Free Regsitration Required]|
The idea is to maximise a function representing the likelihood for obtaining the numbers that are measured. It is denoted U10,T and is expressed as 1? It is neither intended to cover wind conditions experienced during smallscale events such as fast propagating arctic low pressures of limited extension.
For vertical separations, measurements indicate that the model may not hold, possibly owing to a lack of vertical isotropy caused by vertical instability. Most available model spectra are calibrated to wind data obtained over land. Other DNV Recommended Practices give specific information on environmental loading for specific marine structures. Their formation is related to atmospheric instability and is subject to seasonality.
Unless data indicate otherwise, Lu can be calculated as for the Kaimal spectrum, see [2. In rolling terrain, Ax tends to be somewhat larger. The Simiu and Leigh spectrum S f can be obtained from the following equations: Figure shows examples of stability-corrected logarithmic wind profiles for various conditions at a particular location.
The Nataf model should be used with caution due to the simplified modelling of dependency between the variables Bitner-Gregersen and Hagen, For quasi-static response of structures, it is sufficient to use deterministic regular waves characterized by wave length and corresponding wave period, wave height and crest height.
DNV RP C Environmental Conditions and Environmental Loads__图文_百度文库
The transfer functions for finite water depth is given by Sharma and Dean and Marthinsen and Winterstein Unless data indicate otherwise, Lu can be calculated as for the Kaimal spectrum, see 2.
No consensus has been reached neither about a definition of a freak event nor about the probability of occurrence of freak waves. The wave crest in irregular waves can be defined as the global maximum between a positive up-crossing through the mean elevation, and the following down-crossing through the same level.
The difference between the two figures mainly consists in a different shape of the mean curve. The representation of squall wind statistics is a topic for ongoing research.
The phases are random with respect to each other. The integral length scale Lu is in the range m with a mean value of m.
Log in to your subscription
The coefficients C1 and C2 may vary with T1 or Tzand should be determined from measured data. The Forristall crest distribution for wave crest above still water level is based on second order time domain simulations Forristall, A two peak spectrum may be used to account for both wind sea and swell. As a result, the crest will tend to bend towards alignment with the depth contours dv wave crests will tend to become parallel with the shore line.
C20 data indicate otherwise, the integral length scale Lu can be calculated as z 0. Figure gives the wave length as a function of wave period for various water depths.
The expressions should not be extrapolated for use beyond the height range for which they are calibrated, i. In particular, it is important to be aware that the true integral length scale of the wind speed process may deviate significantly from the integral length scale of the model spectrum.
Background In addition, the following companies and authorities have attended project meetings dnb observers, providing useful comments to this new RP. The new RP also includes an improved description and statistical modeling of wind and ocean waves. The deterministic wave parameters may be predicted by statistical methods.
In applications the sea state is usually assumed to be a stationary random process. Analytic wave theories See 3. For details about the von Karman coherence model, reference is made rrp Saranyansoontorn et al. For other applications, a good fit to the main bulk of data might be more important.
The parameters of the joint model fitted to the scatter diagrams are given in Table C Three hours has been introduced as c05 standard time between registrations ro sea states when measuring waves, but the period of stationarity can range from 30 minutes to 10 hours. Note that several swell components may be present at a given location. Usually only quantiles in the upper tail of the distribution are of interest, viz.
The closer together the two points are, the higher is the correlation between their respective wind speeds. For extreme mean wind speeds corresponding to specified return periods in excess of approximately 50 years, the Fr? Expressions for AC, which include the dependency on the wave velocity and the available water fetch, are available in the literature, see Astrup et al. Higher order x205 may result in slightly higher crest heights. While the initial distribution method utilises more data, there is correlation between the observations.
Dbv z and c20 need to be given in units of m. For along-wind turbulence and vertical separations in the range m, coherence decrements in the range are recommended. When wind speed data for other heights than dnc reference height are not available, the wind speeds for the other heights can be calculated from the wind speeds in the reference height in conjunction with a wind speed profile above the ground or above the still water level.
Design Requirements, IEC, 3rd edition, For these reasons, the averaging time for wind speeds and the reference height must always be specified. The MLE has theoretical advantages, but can be cumbersome in practice.
The wave conditions in a sea state can be divided into two classes: Dhv Encyclopedic Dictionary of Applied Geophysics, fourth edition.
This is particularly important when simulating irregular fluid velocities. The Nataf model should be used with caution due to the simplified modelling of dependency between the variables Bitner-Gregersen and Hagen, In contrast, extreme events are more independent, but their scarceness increases statistical uncertainty.