Oral Yagci

Oral Yagci
Istanbul Technical University · Faculty of Civil Engineering

PhD

About

57
Publications
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732
Citations

Publications

Publications (57)
Article
Today, natural rivers are increasingly fragmented by human-made obstacles such as dams. Due to these structures fish populations in natural rivers rapidly diminish. In this context, fishways are a useful hydraulic structure in the creation of ecosystem for fish migration. Three dimensional mean flow and turbulence structure of pool-weir fishways we...
Article
This experimental study presents clear-water scour and deposition patterns around hexagonal arrays of circular cylinders in steady flow conditions. Understanding the scour processes around such configurations could facilitate the design of several hydraulic and marine engineering structures, such as bridge piers and piles. The flow alteration cause...
Article
Full-text available
Instream plants, which act as biological processors, have emerged as potentially advantageous eco-morphologic tools to be used in river management and restoration. Most of the study on the geomorphic role of vegetation as it interacts with flow and sediment has focused on local patch-scale dynamics. In this study, we present flume experiments aimed...
Preprint
Midchannel islands were conventionally considered undesirable additional hydraulic resistance to flow for many years and tended to be removed from the main channel as a measure against the flood. Today, it is known that these geomorphic units provide key eco-geomorphological services in the active corridor of natural waterways. This study examined...
Article
Full-text available
Recent investigations revealed that a group of cylinders offer more advantages than mono-pile when applied as a foundation for offshore wind turbines or pile-supported structures. In this context, the influence of gradually varying unsteady flow around a group of cylinder (Hexagonal arrays of circular cylinders, HACCs) was investigated by flume exp...
Article
Midchannel islands (MCIs) are influential geomorphic units in regulating morphological and ecological dynamics in sand-dominated rivers. The primary objectives of the study were to understand a) the relationship between morphometric characteristics of the basin and the occurrence location of the MCIs, b) the role of MCIs on the hydraulic gradient a...
Article
Full-text available
Hexagonal arrays of circular cylinders (HACCs) can be preferred over mono-piles in the design of marine and hydraulic structures due to certain reasons, e.g. efficiency in scour reduction, decreased stagnation and drag, easier applicability, cost-efficiency. In this study, the influence of the HACC on the flow domain was experimentally investigated...
Preprint
Midchannel islands (MCIs) are influential instream geomorphic units generally emerge in lowland rivers. Despite their significant ecomorphological services in the river ecosystem, the flow structures around these self-forming riparian landforms are not fully understood yet. Understanding the flow pattern around these formations enables practitioner...
Article
Full-text available
Over the last two decades, the role of vegetation in the environmental and ecological restoration of surface water bodies has received much attention. In this context, the momentum exchange between the flow through the main channel and the riparian zone is a key mechanism. The primary goal of this study is to investigate the role of bank vegetation...
Article
The flow field around a vertically mounted circular pile exposed to gradually-varied unsteady flow is experimentally investigated. Experiments were conducted in a 30 m-long and 1 m-wide recirculating flume equipped with a variable discharge pump. A circular cylinder with 9 cm diameter was used as the model pile. To understand the influence of accel...
Preprint
Environmentally friendly piled coastal defence structures gained a particular significance in recent years, given these structures do not interrupt the longshore/cross-shore sediment transport. Flow around an emergent pile is known to generate certain typical coherent flow patterns depending on the flow and boundary conditions, as well as geometry....
Article
Full-text available
Patches of vegetation in natural water bodies grow close to each other and may affect each other’s wake pattern with significant implications on nutrient uptake and local sediment transport. This experimental study analyzed the wakes of two neighboring circular patches of emergent artificial vegetation with different densities, with the tested soli...
Article
The current paper investigates the flow and turbulence characteristics over dune bedforms by means of laboratory experiments, where spatially dense and temporally high frequency velocity measurements were done. Although similar studies are available in the literature, the focus and novelty of the current study is to assess the influence of surface...
Conference Paper
Full-text available
This experimental study investigates the flow field around a vertically mounted circular cylinder exposed to unsteady flow. The spatial variation of Reynolds-averaged velocity and turbulence characteristics around the cylindrical structure is studied in the case of gradually-varying unsteady flow, in comparison with a reference steady flow case. Ri...
Article
Full-text available
The primary objective of this study was to delineate the impact of vegetation on dune erosion under the influence of storm waves. This was achieved through laboratory flume experiments. Specifically, physical model experiments were used to identify the features responsible for coastal dune erosion generated by storm waves under the protection and n...
Article
The present experimental study investigates the scour pattern and the near-wake flow field alteration around an emergent rigid cylinder, which is inclined towards the downstream direction. Three different inclination angles were tested separately, namely 14°, 30°, and 42° with respect to the wall-normal axis. The induced flow and scour patterns wer...
Article
This study aimed to conceptually analyze the change in the magnitude of offshore sediment yield, wave energy, and offshore dislocation of sediment particles on coastal regions in the presence of coastal vegetation. This was achieved by comparing the simultaneous physical changes at coastal zones that were partly covered with vegetation while the re...
Article
In this paper, 3D experiments are conducted aiming at the combined investigation of the hydroelastic and the structural (connectors' internal forces) response of a pontoon-type modular Floating Breakwater (FB), consisting of flexibly connected, moored with chains modules, under the action of perpendicular and oblique regular waves. Regarding the FB...
Article
Full-text available
Riparian and floodplain tree-like emergent vegetation alter significantly the flow field and lead to complicated three-dimensional flow patterns, characterized by increased turbulence production, with the potential to induce morphological changes. The canopy presence in tree-like vegetation leads to the formation of lee wake vortices and can induce...
Article
The complex multi-directional interactions between hydrological, biological and fluvial processes govern the formation and evolution of river landscapes. In this context, as key geomorphological agents, riparian trees are particularly important in trapping sediment and constructing distinct landforms, which subsequently evolve to larger ones. The p...
Conference Paper
Full-text available
The present experimental study investigates the effects of emergent tree-like vegetation on the flow field. Two major flow alteration mechanisms are noted, namely the flow through a porous element and the subcanopy flow. Firstly, a simple artificial porous element simulated the vegetation to deduce the pertinent physical mechanisms. This element co...
Conference Paper
Full-text available
The present experimental study investigates the generated flow field in the presence of a bottom mounted cylinder with a downstream inclination. The experiments were conducted in an 18 m x 0.50 m x 0.50 m flume under steady flow conditions. A cylinder with a diameter of 7.5 cm served as a disturbance to the flow under several inclination angles, pa...
Article
The surface piercing and floating coastal defense structures can be applied as an alternative to conventional rubble mound structures in some specific circumstances. A partially submerged steeply inclined thin plate (ITP) is also one of the candidate alternative structures. Knowledge about the wave attenuation mechanism of ITP improves the engineer...
Conference Paper
Full-text available
Klasik yığma tipi taş dalgakıranlar, kıyı koruma yapısı olarak uzun yıllardır dünyanın pek çok yerinde geleneksel olarak uygulanmaktadır. Ancak bazı durumlarda bu tip yapıların uygulanması güçlükler yaratmaktadır. İnce plakalar gerek tek başlarına, gerekse de taş dolgu dalgakıranlar ile ardışık (tandem) olarak kullanılarak gerekli taş dalgakıran ağ...
Article
This paper presents the results of a 2D experimental model application of an alternative environment-friendly coastal structure, an inclined thin plate (ITP). The primary objectives of this study were to understand (a) wave energy dissipation mechanism of ITP, (b) wave attenuation performance of ITP, and (c) the influence of ITP on water particle (...
Article
The objective of the present paper is the implementation of 3D experiments in order to investigate and assess the structural response (connectors' internal forces and mooring lines' tensions) of a Floating Breakwater (FB) along with its wave attenuation effectiveness under the action of perpendicular and oblique regular and irregular waves. The exa...
Data
Full-text available
In practice, in some cases, tandemly applied pile-mounted horizontal or inclined thin plates emerge as functional coastal structures in terms of diminishing wave height in front of Rubble Mound Breakwaters (RMBs) and consequently, reduce the required armor unit size and RMB's overall weight. In this study, the hydrodynamic performance of an Incline...
Conference Paper
Full-text available
In this paper, 3D experiments are conducted focusing on the structural response (connectors’ and mooring lines’ loads) assessment of a Floating Breakwater (FB) under the action of normal and oblique regular waves. The FB consists of floating modules connected with flexible connectors and moored with chains. The effect of the incident wave character...
Conference Paper
Full-text available
In practice, in some cases, tandemly applied pile-mounted horizontal or inclined thin plates emerge as functional coastal structures in terms of diminishing wave height in front of Rubble Mound Breakwaters (RMBs) and consequently, reduce the required armor unit size and RMB’s overall weight. In this study, the hydrodynamic performance of an Incline...
Article
Coastal vegetation acts as a natural barrier at many coastal zones, protecting the landside against wave effects and coastal erosion. It is known that coastal vegetation affects wave properties, and studies regarding this topic have been made in a wide variety, mostly focusing on wave attenuation. In this study, laboratory experiments have been con...
Article
Although in the past great attention has been devoted to coastal stabilization, the effect of aquatic vegetation on wave characteristics (damping and retardance etc) is still not well known. In this context an experimental study was performed in an irregular wave flume to explore the effect of reeds (phragmites australis) on wave damping and retard...
Article
Flow measurements were conducted by ADV Vectrino to investigate the role of different forms of single natural emergent vegetation elements on kinetic energy characteristics and the flow structure in open channel flow. Experiments were carried out for both forms of “erect” and “compressed” vegetation. The findings revealed that the form of “erect” h...
Article
In this experimental study, measurements were conducted to explore the impacts of different forms of individual natural vegetative elements within the flow domain on velocity and turbulence characteristics. All the experiments were performed in a flume measuring 26 m in length, 0·98 m in width and 0·85 m in depth, and real tree saplings were utiliz...
Article
In this paper the tsunamis resulting from a submarine mass failure such as slides and slumps triggered by earthquakes or other environmental effects, which is settled at the bottom of the north eastern Sea of Marmara are examined in one sample region. As the solution method, one hybrid method is developed. The main objective of this method is to co...
Conference Paper
The present study introduces a physical model of a single emergent and leafy plant in a straight and 1 m wide flume. Two acoustic Doppler velocimeters (ADV) were used to measure vertical profiles of the streamwise and vertical velocity components in the centreline of the wake of the plant. A cypress plant (cupressus macrocarpa) was used in the expe...
Article
Using a three-dimensional finite volume code with standard k-ε turbulence closure the hydraulic impact of willow stands (Salix alba and Salix fragilis) on the velocity distribution was modelled. The additional hydraulic resistance of the willow stands was modelled separately to the bed resistance using a drag force term that was introduced into the...
Article
This paper analyses the results of an application of a piled wavescreen. Experimental measurements were undertaken in the laboratory conditions for a given structural configuration under the attack of regular and irregular waves. Dynamic pressure distribution along and around the inclined piles was obtained employing pressure transducers. Using the...
Article
Full-text available
Recent approaches in two and three‐dimensional numerical models have used a drag force term in the momentum equations to model the stem drag imposed by plants which project through a significant amount of the water depth. This approach reduces the ability to subsume under‐represented processes and data uncertainties in the calibration process which...
Article
The primary objective of the study was to experimentally explore the protection performance of the emergent vegetation on the morphological changes of a coastal zone. The experiments were conducted under both regular and irregular waves in two different wave flumes. A dimensionless number was derived to characterize the beach profile response under...
Article
The anticipation of damage ratio with an acceptable accuracy is a vital issue in breakwater design. The presented study covers the employment of three different artificial neural network methods and a fuzzy model for this problem. Inputs like mean wave period, wave steepness, significant wave height and the breakwater slope are used as input to est...
Conference Paper
Full-text available
Using a three-dimensional finite volume code with standard k-epsilon turbulence model the hydraulic resistance of willows (Salix Alba and Salix Fragilis) are modelled. The drag force approach was used by incorporating an additional term into the Navier-Stokes equations. This method is applied to model a flood event on the Wienfluss test reach in Vi...
Article
The primary aim of the study is to experimentally investigate the stability performance of antifer units on the trunk section of breakwaters under the effect of regular and irregular waves in case of irregular placement. The stability performance tests were conducted for different slopes, i.e. cot α=1.25, 1.5, 2.0, 2.5, under irregular waves and fo...
Article
In this study, a placement technique named as “alternative placement technique” was developed for antifer blocks and the results of its application to a breakwater model were presented. This placement technique was compared with the existing techniques such as the “regular placement technique”, the “irregular placement technique” and the “sloped wa...
Article
Hydrodynamic properties of the Bosphorus Strait (the Strait of Istanbul) were investigated by the three-dimensional computer code named TELEMAC-3D. Distinguished properties of the physical oceanography of the Bosphorus Strait were presented with the accepted theories on the two-way exchange flow within the strait. The position of two liquid boundar...
Article
In breakwater design the determination of armour unit weight is especially important in terms of the structure's life. In a typical experimental breakwater stability study, different wave series composed of different wave heights; wave period and wave steepness characteristics are applied in order to investigate performance the structure. Using a c...

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Project (1)
Archived project
The project deals with the problem of interaction between a vertical cylindrical structure (for instance a bridge pier) and the incident gradually-varied unsteady flow. Not only circular cylinders, but also different hydraulically-streamlined forms, which are used in bridge piers in practice, are studied. In this aspect, the flow characteristics around the cylindrical structures under unsteady flow are investigated, determining the similarities and differences compared to the case of steady flow. The results are of relevance for many different types and scales of unsteady flows in coastal and fluvial environment, such as tsunamis, flood hydrographs, tidal flows, meteorology-driven flows.