Civil Engineering / İnşaat Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/13
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Article Citation - WoS: 15Citation - Scopus: 18Extreme Value Statistics of Wind Speed and Wave Height of the Marmara Sea Based on Combined Radar Altimeter Data(Elsevier, 2019) Özbahçeci, BergüzarBoth reliable and long-term wind and wave data are necessary for the design of coastal and offshore structures. Due to lack of sufficient in-situ measurement data, modeling data have been used in the limited number of wind and wave climate studies of the Marmara Sea. Satellites equipped with instruments capable of observing marine surface wind and ocean waves like Radar Altimeter can be another source for the long term wind and wave climate of the Marmara Sea. In this study, for the first time, the altimeter wind speed and the significant wave height data from different satellite missions are attempted to use in the climate and extreme value analysis of the Marmara Sea. Altimeter wind speeds and significant wave heights are compared with the in-situ measurements and it is found that while the altimeter wind speed agrees with the measurement data, the significant wave height data should be calibrated. After the calibration of the altimeter data and the inter-calibrations of earlier satellite missions, 27 years of altimeter wind speed and wave height data are obtained to use in extreme value analysis. The wind speed and the significant wave height values corresponding to various return periods are determined as a result of extreme value statistics and those values are compared with the results of the measurements and previous studies. Consistent extreme values computed in the current study indicate that the combined radar altimeter data can be used in the wind and the wave climate calculations and the extreme value analysis of the Marmara Sea. © 2019 COSPARArticle Citation - WoS: 6Citation - Scopus: 6Calibration and Verification of Century Based Wave Climate Data Record Along the Turkish Coasts Using Satellite Altimeter Data(Elsevier Ltd., 2020) Özbahçeci, Bergüzar; Turgut, Ahmet Rıza; Bozoklu, Ahmet; Abdalla, S.In order to produce consistent reanalysis of the climate system, ECMWF (The European Centre for Medium-Range Weather Forecasts) has produced firstly an uncoupled atmospheric reanalysis ERA-20C, and then a coupled climate reanalysis, called CERA-20C, which covers the period January 1900 to December 2010. Both data sets are available at 3-hour time increments. Such a century long data can be an alternative to calculate the extreme waves corresponding to low probability of occurrences without extrapolation of extreme value statistics’ results which may contribute to the error in the estimation of design waves in case of small number of wave data. In this study, main purpose is to calibrate and verify the century-based wave data in order to derive the longest and the consistent wave data along the Turkish coasts as a first time to be used in the extreme wave analysis. For this purpose, first of all, significant wave height data of ERA-20C and CERA-20C are compared by using ENVISAT data over the whole Black Sea for 2007–2008 as a pilot study. Comparison results show that both datasets give similar results but CERA-20C seems to be better in terms of statistical error measures. Then CERA-20C significant wave height data are calibrated using satellite Radar Altimeter data set. Jason family of satellites (TOPEX, Jason-1 and 2) and Envisat family of satellites (ERS-2 and Envisat) are inter-calibrated to get the consistent satellite data sets with a total duration of 18 years (1995–2012) for Envisat family and 26 years (1992–2017) for Jason family in order to be used in calibration of CERA-20C wave height. The mean wave period is also estimated from RA backscatter coefficients (Ku and C bands) and the significant wave height by using Artificial Neural Network Method. Then the estimated mean wave periods are used for the calibration of CERA-20C wave period. Calibrated CERA-20C data are compared with in-situ measurements for the verification purposes. Results of verification study show that the calibrated CERA-20C wave data agree well with the in-situ measurements in terms of Quantile-Quantile analysis with lower deviations from y = x line and capture the largest sea states. In fact, CERA-20C, century-based wave data become appropriate to determine the extreme waves to be used in the design of coastal structures along the Turkish coasts. © 2020 COSPARArticle Citation - WoS: 1Citation - Scopus: 3Effect of the Armor Crest Freeboard Relative To the Crown Wall Freeboard on Wave Overtopping for Simple Rubble Mound Slopes(Elsevier Ltd., 2018) Özbahçeci, Bergüzar; Bilyay, EnginSeveral studies have been carried out to investigate the effect of crest parameters on the wave overtopping for armored slopes with crown walls. However, the effect of the armor crest freeboard is still under question. In this study, for the first time, a series of hydraulic model experiments are conducted specifically to investigate how the armor crest freeboard relative to the crown wall freeboard affects the wave overtopping rate. Experimental results indicate that while the armor crest freeboard lower than the crown wall freeboard is giving larger overtopping, higher armor crest freeboard is reducing the overtopping. However, this reduction is not same as the reduction due to the increase in the crown wall freeboard. The reason may be the porosity of the armor crest. For the first time, a new correction factor is proposed to describe the change in the wave overtopping due to the armor crest freeboard by using experimental results. The correction factor C Ac is applied to cover the effect of armor crest freeboard in the predictions of EurOtop (2016). The verification study present that overtopping rate predictions of corrected EurOtop (2016) are more consistent with the measured rate results compared to the predictions of the original formula, if the armor crest freeboard is not equal to the crown wall freeboard.