Effect of intrinsic and sampling variability on wave parameters and wave statistics

2014 ◽  
Vol 64 (11) ◽  
pp. 1643-1655 ◽  
Author(s):  
Elzbieta M. Bitner-Gregersen ◽  
Anne Karin Magnusson
Keyword(s):  
Sampling Variability ◽  
Wave Statistics ◽  
Wave Parameters

Wave Distributions and Sampling Variability

2007 ◽  
Author(s):  
O̸istein Hagen
Keyword(s):  
Wave Height ◽  
Extreme Values ◽  
Height Distribution ◽  
Short Term ◽  
Sea State ◽  
Sampling Variability ◽  
Wave Statistics ◽  
Individual Wave ◽  
Wave Heights ◽  
Crest Height

The paper describes the effect of sampling variability on the predicted extreme individual wave height and the predicted extreme individual crests height for long return periods, such as for the 100-year maximum wave height and 100-year maximum crest height. We show that the effect of sampling variability is different for individual crest or wave height as compared to for significant wave height. The short term wave statistics is modeled by the Forristall crest height distribution and the Forristall wave height distribution [3,4]. Samples from the 3-hour Weibull distribution are simulated for 100.000 years period, and the 100-year extreme values for wave heights and crest heights determined for respectively 20 minute and 3 hour sea states. The simulations are compared to results obtained by probabilistic analysis. The paper shows that state of the art analysis approaches using the Forristall distributions give about unbiased estimates for extreme individual crest or wave height if implemented appropriately. Direct application of the Forristall distributions for 3-hour sea state parameters give long term extremes that are biased low, and it is shown how the short term distributions can be modified such that consistent results for 20 minute and 3 hour sea states are obtained. These modified distributions are expected applicable for predictions based on hindcast sea state statistics and for the environmental contour approach.

scholarly journals Challenges in Description of Nonlinear Waves Due to Sampling Variability

2020 ◽  
Vol 8 (4) ◽  
pp. 279
Author(s):  
Elzbieta M. Bitner-Gregersen ◽  
Odin Gramstad ◽  
Anne Karin Magnusson ◽  
Mika Malila
Keyword(s):  
Numerical Simulations ◽  
Second Order ◽  
Intrinsic Variability ◽  
Third Order ◽  
Design Work ◽  
Sampling Variability ◽  
Mean Values ◽  
Wave Parameters ◽  
Temporal And Spatial ◽  
Numerical Solver

Wave description is affected by several uncertainties, with sampling variability due to limited number of observations being one of them. Ideally, temporal/spatial wave registrations should be as large as possible to eliminate this uncertainty. This is difficult to reach in nature, where stationarity of sea states is an issue, but it can in principle be obtained in laboratory tests and numerical simulations, where initial wave conditions can be kept constant and intrinsic variability can be accounted for by changing random seeds for each run. Using linear, second-order, and third-order unidirectional numerical simulations, we compare temporal and spatial statistics of selected wave parameters and show how sampling variability affects their estimators. The JONSWAP spectrum with gamma peakedness parameters γ = 1, 3.3, and 6 is used in the analysis. The third-order wave data are simulated by a numerical solver based on the higher-order spectral method which includes the leading-order nonlinear dynamical effects. Field data support the analysis. We demonstrate that the nonlinear wave field including dynamical effects is more sensitive to sampling variability than the second-order and linear ones. Furthermore, we show that the mean values of temporal and spatial wave parameters can be equal if the number of simulations is sufficiently large. Consequences for design work are discussed.

Observations and Modeling of Linear and Nonlinear Spatio-Temporal Wave Statistics

2010 ◽  
Author(s):  
Leonel Romero ◽  
W. Kendall Melville
Keyword(s):  
Spatial Information ◽  
Second Order ◽  
Stochastic Simulations ◽  
Ocean Engineering ◽  
Engineering Applications ◽  
Large Wave ◽  
Wave Statistics ◽  
Wave Parameters ◽  
Wave Heights ◽  
Spatio Temporal

We present an analysis of airborne wave observations collected in the Gulf of Tehuantepec. The data includes LIDAR measurements of the surface displacement as a function of two horizontal dimensions and time in fetch-limited conditions, with fetches between 50 and 300 km and winds between 10 and 20 m/s. The spatio-temporal data have an advantage over the commonly used single point time-series measurements allowing direct estimates of the wavelength and wave slope, including spatial information such as the lengths of crests exceeding threshold wave heights and slopes. The statistics of these wave parameters are particularly important for risk assessment of off-shore structures and in other ocean engineering applications. We present an analysis of several statistical wind-wave parameters, including the joint probability distribution function (pdf) of wave amplitudes and wavelengths, the pdf of wave heights, wavenumber vectors, and wave slopes, including the statistics of crests lengths exceeding threshold wave heights or slopes. The empirical findings from the LIDAR data are related to the analytical work by Longuet-Higgins (1957) [1] for a linear spectrum, including the average length of contours surrounding large wave heights. The effect of second-order nonlinearities on the distribution of crest lengths is investigated with numerical stochastic simulations from computed directional wavenumber spectra. The results show that second-order nonlinearities can increase the crest length density of large waves by about a factor of two or more. The results are discussed in the context of predicting wave statistics for ocean engineering applications.

Comparison of Temporal and Spatial Statistics of Nonlinear Waves

2019 ◽  
Author(s):  
Elzbieta M. Bitner-Gregersen ◽  
Odin Gramstad
Keyword(s):  
Spatial Statistics ◽  
Modulational Instability ◽  
Rogue Waves ◽  
Nonlinear Dynamical ◽  
Wave Statistics ◽  
Wave Data ◽  
Camera Systems ◽  
Wave Parameters ◽  
Temporal And Spatial ◽  
Numerical Solver

Abstract In the past, it was most common to derive wave parameters and their statistics from time series of wave elevation. The duration of the wave records has been usually restricted to 20 or 30 minutes. Recently, increasing attention has started to be given to spatial wave data and wave statistics, particularly due to introduction in oceanography of stereo camera systems for collecting space–time ensemble of sea surface elevation. Using numerical linear, 2nd and 3rd order simulations this study compares temporal and spatial statistics of wave parameters. The 3rd order wave data are simulated by a numerical solver based on the Higher Order Spectral Method (HOSM) which includes the leading order nonlinear dynamical effects, accounting for the effect of modulational instability. The Pierson-Moskowitz and the JONSWAP spectrum with different gamma parameters are used in the analysis. Sea states with wave steepness where rogue waves were recorded in nature are considered. Consequences of using temporal contra spatial statistics are discussed in perspective of marine structures’ design. Functional dependency between wave parameters characterizing occurrence of rogue waves in unidirectional wave field is proposed.

Estimation of Onsite Wave Parameters From the WindFloat Platform

2013 ◽  
Author(s):  
Antoine Peiffer ◽  
Nathan Tom ◽  
Christian Cermelli ◽  
Dominique Roddier
Keyword(s):  
Wave Spectra ◽  
Wave Direction ◽  
Wave Statistics ◽  
Wave Measurements ◽  
Wave Parameters ◽  
Floating Foundation ◽  
Wave Elevation ◽  
Many Instruments ◽  
Directional Wave ◽  
Buoy Measurements

The WindFloat is a semi-submersible floating foundation supporting multi-megawatt wind turbines. A full-scale 2MW WindFloat demonstration unit was installed off the coast of Portugal in October 2011. Many instruments are installed on this prototype to measure the environmental conditions and the response of the platform at the site. The first section of the paper focuses on the validation of the wave measurements obtained from two radar-based wave probes onboard the platform. The wave elevation at the site is reconstructed and typical wave statistics are computed. The results are compared and validated with independent buoy measurements close to site. The second section of the paper presents estimates of prevailing wave direction and directional wave spectra based on platform motions. These results are also benchmarked with onsite buoy measurements.

Maneuvering and Seakeeping Basin Wave Characterization Study

2017 ◽  
Author(s):  
Miguel Quintero ◽  
Samantha Lee
Keyword(s):  
Spatial Variability ◽  
Deep Trench ◽  
Wave Condition ◽  
Wave Statistics ◽  
Wave Parameters ◽  
Characterization Study ◽  
Series Of Experiments ◽  
Directional Wave ◽  
Fixed Array ◽  
Naval Surface Warfare

A series of experiments aimed at characterizing the wavefield generated by the new multi-directional wave making system in the Maneuvering and Seakeeping (MASK) Basin at the Naval Surface Warfare Center Carderock Division in West Bethesda, MD are described. These experiments were focused on the repeatability of phase resolved seaways, the spatial variability of wave parameters throughout the basin, and the stationarity of the wavefield over the span of 2 hours. Two different wave spectra were run repeatedly over a two week test window covering 21 discrete locations with one fixed array of sensors as a control. The results from the test show that when sampling at the same location and running the same wave condition, the phase resolved seaway exhibits a coherence of over 95% between 0.25 and 0.75 Hz. The spatial variability of the wave statistics proved to be within 5% of the average values throughout the tank, with a larger deviation over the 35ft deep trench section.

Modelling of detonation wave parameters, initiation and hazard of chemically active bubble systems

2002 ◽  
Vol 12 (7) ◽  
pp. 403-412 ◽  
Author(s):  
P. A. Fomin ◽  
K. Mitropetros ◽  
H. Hieronymus ◽  
J. Steinbach
Keyword(s):  
Detonation Wave ◽  
Wave Parameters

Measurement of surface-wave statistics

1974 ◽  
Author(s):  
H. GUTHART ◽  
K. KRISHNAN ◽  
N. PEPPERS
Keyword(s):  
Surface Wave ◽  
Wave Statistics

WAVE CLIMATE OF THE BLACK SEA’S COASTAL WATERS DURING THE LAST THREE DECADES

2017 ◽  
Author(s):  
Fedor Gippius ◽  
Fedor Gippius ◽  
Stanislav Myslenkov ◽  
Stanislav Myslenkov ◽  
Elena Stoliarova ◽  
...  
Keyword(s):  
Wind Speed ◽  
Cell Size ◽  
Coastal Waters ◽  
Wind Wave ◽  
Spatial Scales ◽  
Wave Model ◽  
Wave Climate ◽  
Computational Grid ◽  
Coastal Areas ◽  
Wave Parameters

This study is focused on the alterations and typical features of the wind wave climate of the Black Sea’s coastal waters since 1979 till nowadays. Wind wave parameters were calculated by means of the 3rd-generation numerical spectral wind wave model SWAN, which is widely used on various spatial scales – both coastal waters and open seas. Data on wind speed and direction from the NCEP CFSR reanalysis were used as forcing. The computations were performed on an unstructured computational grid with cell size depending on the distance from the shoreline. Modeling results were applied to evaluate the main characteristics of the wind wave in various coastal areas of the sea.

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