Browsing by Author "Jafali, Halid"
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Item Downscaling of wave climate in the western Black Sea(Pergamon-Elsevier Science, 2018-11-15) Akpınar, Adem; Jafali, Halid; Vledder, Gerbrant Ph Van; Bingölbali, Bilal; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/İnşaat Mühendisliği Bölümü.; 0000-0003-4496-5974; AAB-4152-2020; 57189584264This study presents the south-west Black Sea wave climatology based on a downscaling approach of a long-term 31-year SWAN model wave hindcast using telescoping nested grids. At all domains the SWAN model is forced with the CFSR winds. Sensitivity tests are conducted on domain size, computational resolutions, the physical formulations and their adjustable coefficients for deep water source terms, time step of non-stationary calculation, and wind forcing for all domains. For each nested grid the physical and numerical settings were determined separately by calibration against wave buoy measurements at six locations (Gelendzhik, Hopa, Sinop, Gloria, Filyos, and Karaburun) in appropriate domains. Model validation is also conducted for the long-term data using the unused measurements in the calibration. Using the calibrated nested models, a 31-year long-term wave hindcast is conducted. Two-hourly sea state parameters of significant wave height (Haw), wave energy period (Tm-10), spectral period (T-m01), zero-crossing period (T-m02), peak period (T-p), wind speed components, and mean wave direction (DIR) were collected over three sub-grid domains. Using this database normal and extreme wave conditions in the three sub-grid domains were determined. Finally, extreme waves with different return periods were determined and compared with those presented in the Wind and Deep Water Wave Atlas of Ozhan and Abdalla (2002). The present study demonstrates the sensitivity of the SWAN model towards different GEN3 physics options and its adjustable whitecapping parameter C-ds and time step of the non-stationary calculations. It is shown that the developed wave model set-up with a nested grid system performs quite satisfactorily and storms are also well-captured. This study yields higher extreme waves in the western part of our area of interest and lower extremes in the eastern part in comparison with those of the presently used Wind and Deep Water Wave Atlas.Publication Downscaling wave energy converters for optimum performance in low-energy seas(Elsevier, 2021-05-01) Iglesias, Gregorio; Majidi, AjabGul; Bingolbali, Bilal; BİNGÖLBALİ, BİLAL; Akpinar, Adem; AKPINAR, ADEM; Jafali, Halid; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi.; 0000-0003-0006-5843; 0000-0003-4496-5974; 0000-0002-5422-0119; AAB-4152-2020; AAC-8011-2021; AAC-6763-2019As wave energy converters (WECs) are typically designed and optimized for ocean wave conditions, they struggle to perform in low-energy seas or bays, where wave conditions are very different. This work investigates the hypothesis that downscaled versions of WECs may well be more suited for such conditions. More specifically, fifteen downscaled WECs are considered for deployment in the Black Sea. The resizing (downscaling) of the WECs is based on Froude scaling law. Ten values are considered for the scaling factor (lambda(L) = 1/4 1.0, 0.9, 0.8 ... 0.1), and the value that yields the highest capacity factor is selected for downscaling the WEC. The downscaled WEC is then compared with the original (full-scale) WEC in terms of performance (capacity factor, full-load hours, and rated capacity). This analysis is carried out for fifteen WECs and 62 locations at different water depths (5, 25, 50, 75, and 100 m), distributed on 13 lines perpendicular to the shoreline along the south-western coast of the Black Sea. The highest capacity factor was obtained by Oyster, whereas the highest energy output was achieved by SSG and WaveDragon for the locations with 4-16 m depths. For deeper waters (25, 50, 75, and 100 m), the highest capacity factor was obtained by Oceantec. In terms of energy output, the best performers were WaveDragon (at 25 m water depth) and Pontoon (at 50, 75, and 100 m water depths). The interest of this approach, however, lies not only in that it enables a scaling factor to be determined for downscaling a WEC for a given site, but also and more generally in that it proves the initial hypothesis that downscaled WECs may provide a better alternative for low-energy seas than their full-scale counterparts.Item Temporal variation of the wave energy flux in hotspot areas of the Black sea(Mdpi, 2019-01-21) Rusu, Eugen; Akpınar, Adem; Jafali, Halid; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/İnşaat Mühendisliği Bölümü.; 0000-0002-9042-6851; AAC-6763-2019; ABE-8817-2020; 23026855400; 57205266652This paper aims to examine the temporal variation of wave energy flux in the hotspot areas of the Black Sea. For this purpose, a 31-year long-term wave dataset produced by using a three-layered nested modelling system was used. Temporal variations of wave energy were determined at hourly, monthly, seasonal, and yearly basis at seventeen stations. Based on the results obtained, it can be concluded that the stations have very low fluctuations in mean wave power during the day. Mean wave power in the summer months shows a low difference between the stations, but in the winter months, there is a higher difference in wave power between the stations. This difference is more at the stations in the southwestern part of the Black Sea and much lower in the eastern Black Sea stations around Sinop, being in the middle of the southern coast of the Black Sea. In addition, it is concluded that mean wave energy flux presents a decreasing trend at all stations, but maximum wave power offers an increasing trend at most of the stations.Item Wave energy potential and variability for the south west coasts of the Black Sea: The WEB-based wave energy atlas(Pergamon-Elsevier Science, 2020-06-16) Bekiroğlu, Serkan; Bilal, Bingölbali; Jafali, Halid; Akpınar, Adem; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/İnşaat Mühendisliği.; 0000-0002-9042-6851; 0000-0003-4496-5974; AAB-4152-2020; FAC-5753-2022; AAC-6763-2019; 57189584264; 57205266652; 23026855400This study aims at the assessment of wave energy potential and its spatial and temporal variability along the south-west coasts in the hot-spot areas of Black Sea. For this purpose, third-generation numerical wave hindcast model Simulating WAve Nearshore (SWAN), which is based on a set of nested SWAN model with increasing spatial resolutions (a coarse grid, then a fine grid, and then three sub-grids), forced with the Climate Forecast System Reanalysis (CFSR) winds is used to produce long term wave characteristics during the 31 years in the areas of interest. For the south-west coasts of the Black Sea the best nested SWAN model configuration, developed in our previous studies [1,2], with tuned coefficients for all of the deep and shallow water source terms in modelling of the wind-generated waves is run to obtain spatial and temporal outputs of several wind wave parameters for the assessment of wave energy potential and its variability. By using this data set, temporal and spatial variability of wave energy potential along the south western Black Sea is analysed in detail, considering annual, seasonal, and monthly spatial variation maps of wave power for each of the sub-grids. In addition, annual, seasonal, and monthly wave power potential variability, the exceedance probability curves, the value of wave energy resource potential, and wave power roses are established for several locations. The value of energy density, spatial variation of the stability of energy density (the coefficient of variation, monthly variability index, seasonal variability index, and persistency analysis), spatial variation of total storage and exploitable storage of wave energy resource are also analysed. Finally, it was determined that in the regions (Karaburun SD3 sub-grid domain) where the average wave energy flux is high, the wave energy flux has a high coefficient of variation, and thus the regions (Filyos SD2 sub-grid domain) having lower wave energy flux have a stable wave energy flux which is ideal for energy exploitation from waves. Annual average wave energy in the southwestern part of the Black Sea is concentrated at 0.2-1.5 m significant wave height range, and also the concentration is between 2 and 5 s in Karaburun SD3, 3-7 s in Filyos SD2 and 2.5-6.5 s in Sinop SD1 sub-grid domains in terms of the wave energy period.