Liman ulaşım kanallarında kumlanma analizi ve uygulayıcılar için basitleştirilmiş bir model
Sedimentation analysis in harbour approach channels and a basic model for practitioners
Yazar: SELMAN BAYSAL
Danışman: DOÇ. DR. VEYSEL ŞADAN ÖZGÜR KIRCA
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Kıyı Bilimleri ve Mühendisliği Ana Bilim Dalı / Kıyı Bilimleri ve Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2018
Konu: Deniz Bilimleri = Marine Science ; İnşaat Mühendisliği = Civil Engineering
Dizin: Kıyı morfolojisi = Coastal morphology ; Kıyı mühendisliği = Coastal engineering

Özet:
Dünyamız her geçen gün globalleşmekte, insan nüfusu ciddi sayılara ulaşmaktadır. Bunun bir sonucu olarak, diğer ulaşım türlerine göre daha az maliyetli oluşu ve daha çok malzemenin/insanın taşınabilirliği sebebiyle deniz yolu taşımacılığı giderek önem kazanmaktadır. Artan gemi boyutları ve sayısı ile mevcut limanlardan daha büyük limanlar inşa edilmekte; mevcut limanların kapasiteleri arttırılmak istenmektedir.
Sunulan bu çalışma ile standartlarda belirtilen farklı yaklaşımlar irdelenerek, artan ihtiyaçlara cevap verebilecek sürdürülebilir bir liman ulaşım kanalında güvenli operasyon koşulları için kanal tarama sıklıklarının belirlenmesi amaçlanmıştır. Bu amaç doğrultusunda, dünyada mevcut olan gemi tipleri içerisinden referans alınan tasarım gemilerinin ağırlık, uzunluk, genişlik gibi karakteristik özellikleri göz önüne alınarak çalışma bölgesindeki meteorolojik ve oşinografik koşullar ile çevresel faktörler altında ulaşım kanalları tasarlanmıştır. Bu noktada idealleştirilmiş bir ulaşım kanalı enkesiti göz önüne alınarak dalga ve akıntıların bu kanala dik etkidiği kabulü yapılmıştır. Tasarlanan ulaşım kanallarında farklı tasarım gemileri için mevcut koşullarda katı madde hareketi analizi yapılarak ulaşım kanallarında biriken katı madde miktarı belirlenmiştir. Böylece, operasyonel kısıtlara ve koşullara uygun şekilde tasarlanan ulaşım kanallarında ne kadar sıklıkla tarama yapılması gerektiği ortaya konmuştur.
Çalışmada, tasarım gemileri seçiminde ROM 3.1-99 (2007) ve PIANC (2014) standartları ile sunulan verilerden yararlanılmıştır. Günümüzde mevcut bulunan gemilerin ve bu gemilerin özelliklerinin yer aldığı tablolardan yararlanılarak, gelecekte var olması mümkün detveyt tona sahip gemiler için gemi boyutları ve bu boyutlara bağlı olarak tasarlanması gereken ulaşım kanalı geometrileri ortaya konmuştur.
Bu çalışma süresince Türkiye denizleri için (özellikle Karadeniz için) mevcut olan meteorolojik ve oşinografik veriler ile çevresel koşullar referans alınmıştır. Bu veriler kullanılarak katı madde hareketi analizleri yapılmıştır. Toplam katı madde debisini oluşturan askıda katı malzeme debisi ve taban malzemesi debisi, dalga ve akıntı etkisi altında belirlenmiştir. Taban malzemesi taşınım hesaplarında Shields parametresinin zamana bağlı değişimi Soulsby (1997) tarafından önerilen yöntemlerle; tabanda bu parametreye bağlı olarak oluşan ve taban malzemesi debisini etkileyen tepe ve çukur şeklindeki yapıların geometrileri Nielsen (1979) yöntemi ile; elde edilen bulgular kullanılarak taban malzemesi debileri ise Engelund ve Fredsoe (1976) formülasyonları ile belirlenmiştir. Askıda katı madde debisi ise van Rijn ve Walstra (2004) yaklaşımı kullanılarak elde edilen askıda katı madde konsantrasyonu değerleri ile bu derinlikte olan ve Soulsby (1997) yaklaşımı ile belirlenen zamansal ortalama akıntı hızlarından yararlanılarak elde edilmiştir.
Çalışmanın amacı olan tasarlanan ulaşım kanalında birim genişlikte biriken katı madde hacmini belirlemek için, süreklilik denkleminden türetilen tek boyutlu Exner denklemi kullanılmış; ulaşım kanalı şevinde biriken malzemenin birikme geometrisi kanal şevine paralel olacak şekilde idealize edilmiştir.
Octave GNU dilini kullanan bir sayısal model ile gerçekleştirilen bu çalışma sonucunda elde edilen bulgular değerlendirilerek, katı madde taşınımına etki eden faktörlerin ulaşım kanalı tarama sıklığı değerlerine etkileri incelenmiştir. Referans tasarım gemiler ile fiziksel ve çevresel verilerin göz önüne alındığı bu çalışmanın farklı koşullarda değerlendirilebilmesi amacıyla elde edilen bulgular boyutsuzlaştırılarak okuyucuya sunulmuştur.
Model sonuçları sonunda görülmüştür ki hazırlanan sayısal model, farklı meteo-oşinografik ve çevresel faktörler göz önüne alındığında kendi içinde tutarlı ve sektörde yapılan çalışmalar ile uygun sonuçlar vermektedir. Bu bağlamda, çalışma ile amaçlanan, araştırmacılara ve uygulayıcılara mevcut koşullar ve gelecekte doğabilecek ihtiyaçlar doğrultusunda tasarlanması planlanan liman ulaşım kanallarında boyutlandırma yapılması ve ulaşım kanalı tarama sıklıklarının belirlenmesi için pratik bir sayısal model sunulmuştur.

Abstract:
Sea transportation has played a major role in the development of civilizations throughout human history and in their communication with each other. Sea transportation from 4000 BC to the present was developed in the Industrial Revolution, especially through the invention of steam engines. When the historical process is examined, the development and importance of maritime transportation and trade is seen.
Each day, the world becomes more globalized and human population increases seriously. Sea transportation, as a consequence, becomes more significant because it is less costly and provides transformation of more materials/people than other types of transportation. As a consequence of the increasing demand, the number and size of ships and harbours become unsatisfactory. In order to meet such needs, larger ports are constructed in relation to increasing ship size and number, and capacities of existing ports are expected to be increased.
The dimensioning and positioning of harbour approach channels, which are described as the waterway providing access to the manoeuvring area inside the port from open sea, is of great importance since ensuring safety in sea transportation through dredging process and removing dredged materials are economically very significant. The objective of this study is to examine different approaches and to determine the channel dredging frequency for safe operation conditions in a sustainable port that can meet the increasing demand.
In this respect, considering the characteristics of different types of reference ships such as weight, length, and width, harbour approach channels under meteorological, oceanographic and environmental factors were designed. Taking the idealized approach channel cross-section into account, it was assumed that the waves and currents were perpendicular to this channel. This situation refers to the undesired condition for designing of approach channels. In this way, it can be said that the most critical situations in reference conditions were considered.
Approach channels are idealised in three different types in the literature: canal, restricted channel and unrestricted channel. In this study, what we mean by approach channel is restricted channels. The design of restricted channels includes determining the direction, width and depth of approach channel. Throughout the study, straight channels were studied, and the widths and depths of the channels were determined under different design vessels and reference conditions. The concept design steps proposed by PIANC (2014) and proposed by AYGM (2016) were followed in horizontal and vertical channel dimensioning. The results were presented to the reader for one-way approach channels, although they were available for two-way approach channels.
In this study, in the selection of design ships, ROM 3.1-99 (2007) and PIANC (2014) data were benefited. The design ship is defined as the largest vessel to be used in port. Considering the needs and the ship characteristics, this definition seems to be insufficient. For this reason, three different ship types were selected as design vessels. These were a 200000 DWT bulk carrier, a 150000 DWT tanker and a 125000 DWT container ship. In the selection of these vessels, the vessels were of different types and had approximately the same width. The numerical model developed within the scope of the thesis and intended to be presented to the appliers can produce solutions for the tonnage determined by the appliers for all types of ships presented in the above standards except for these reference design ships. Moreover, by using the tables giving information about current ships and their features, possible ship dimensions and harbour approach channels in relation to those ships were put forth for ships which might be constructed in the near future. Although these results are not expressed in this work as they do not serve the purpose of the thesis, it can be seen from the given graphs that the numerical model can successfully solve this process.
The properties of fluid and sediment should be known in order to understand the meaning of the results obtained. Throughout the study, the fluid environment was accepted as the sea water with an average salinity (3.5%) in oceans. The solid material was fine sand, and the reference median grain diameter was 0.2 mm. Within the scope of the study, the dredging frequency for the fine sand with different median grain diameter was presented to the reader.
In the scope of this study, meteorological and oceanographic data and existing environmental conditions for the seas of Turkey were taken as a reference. When the findings of the study are taken into account, it is seen that the data (wave climate and current characteristics) are especially compatible with the Black Sea data. In the approach channels outside the surf zone, wave-generated currents were neglected and the reference depth-averaged current velocity was taken 0.1 m/s. The flow rate and the characteristic wave parameters in different situations, playing a major role in the process of sediment transportation, were also taken into account and total sediment transport processes were performed by using these data. 
In the designed approach channels, by analyzing sediment transportation process, the amount of sediment deposited in the approach channels for all the reference design ships was determined. This process, which is also named sedimentation in harbour approach channels, was analyzed under two different mechanisms: bed load transport and suspended sediment transport. 
For very slow wave and/or current flows over the bed, bed materials remain immobile, i.e. there is no motion, and the bed remains flat. The Shield criteria was taken into account for the initiation of the motion of bed material accepted as stationary on sea bed. Materials that met the Shields criteria were considered to be in motion. Sediment is called bed load if it moves in contact with sea bed in the most of the sediment transport process, whereas, if it moves in suspension in general, it is called suspended load. The suspended load transport rate and the bed load transport rate, constituting the total sediment discharge, were determined under the influence of wave plus current. The time-dependent change of the Shields parameters for the calculation of the bed load was determined through the use of methods proposed by Soulsby (1997), while the Nielsen method (1979) was used in order to calculate the geometry of ripples formed in relation to the Shields parameters and affecting bed load transport rate. By using the data obtained, the bed load transport was determined through the Engelund and Fredsoe (1976) formulations. The suspended load transport rate was found out by using the suspended load concentration values obtained by means of the van Rijn and Walstra (2004) approach and the time-averaged flow velocity determined by the Soulsby (1997) method. This study was repeated with the above mentioned parameters that were different from the reference data. Thus, it was demonstrated how the median grain diameter, current velocity and wave height/period parameters, known to have non-negligible effects on sediment transport mechanism, affected this process.
In light of the results obtained, in order to determine the volume of the deposited sediment in unit width in the designed approach channels, which is also the objective of this study, the one dimensional Exner equation derived from the continuity equation was used, and the geometry of the sediment accumulated in the approach channel slope was idealized to be parallel to the channel slope. Therefore, in order to overcome operational constraints and to ensure operational conditions, how often the designed approach channels should be dredged, i.e dredging frequencies, was demonstrated.
This study was carried out through a numerical model by using the Octave GNU language, and the results were evaluated and the impacts of the factors, affecting sediment transportation, on the dredging frequency values of the approach channels were examined. The results of this study, focusing on reference design ships, metocean and environmental data, were presented to the reader by non-dimensionalising them in order to evaluate it under different conditions.
As a result of this study, it is seen that the numerical model gives consistent results with the studies in the literature for different metocean and environmental factors. Moreover, for researchers and practitioners, a practical numerical model is proposed for the purpose of determining the dimensions of harbour approach channels and channel dredging frequencies for current conditions and future requirements.