Omer Kemal Kinaci

Istanbul Technical University · Faculty of Naval Architecture and Ocean Engineering

In two-dimensional experimental setups, tip-flow cannot be eliminated completely. In one degree-of-freedom Flow Induced Motions (FIM) of circular cylinders placed perpendicular to a uniform flow, three-dimensional effects may become significant. An ideal setup extends the cylinder to the limits of the flow-channel to minimize tip vortices, which re...

In conjunction with high performance computers, recent developments in computational science paved the path to more accurate representation of body motions inside fluids. Small motions inside the flow can be computationally approximated by using deforming grid but deforming grids are incapable of accurately predicting the large motions of a planing...

Computational fluid dynamics (CFD) that implement finite volume method are offering accurate and precise solutions for ship roll problem. In this study, the free roll decay of the benchmark DTMB 5415 hull with bilge keels in calm water was numerically solved by applying this type of code. Contributions of viscosity, wave, eddy and forward ship spee...

In this study, a new developed code, MANSIM (MANeuvering SIMulation) for ship maneuvering simulations and its theoretical background are introduced. To investigate the maneuverability of any low-speed ship with single-rudder/single-propeller (SPSR) or twin-rudder/twin-propeller (TPTR) configurations, a 3-DOF modular mathematical model or empirical...

Course-keeping ability of a ship maintains its stability during surge. Although a ship might have a symmetric hull form, the propeller rotation creates asymmetry in the flow leading to path deviations in straight-ahead condition. When there are additional asymmetries involved in other appendages (such as the rudder), this deviation might be greater...

Hydrokinetic energy from vortex-induced vibrations (VIV) have become popular recently. The potential is higher in seas and oceans but the technology is also applicable in rivers. However, many rivers in the world have limited depths and the VIV response heavily depends on the boundaries. In this study, we focus on the free-surface effects on the VI...

Smooth, rigid, circular cylinders on elastic support in flow perpendicular to their axis undergo vortex-induced vibrations (VIV) over a broad range of velocities. VIV converts hydrokinetic energy to mechanical in the oscillating cylinder. Tip-flow introduces three dimensional effects reducing the effective length of the cylinder which provides the...

Studies involving vortex-induced vibrations (VIV) are generally conducted in water when the mass ratio is low and in air when it is high. VIV in water gained much attention in the last decade due to the possibility of harnessing hydrokinetic energy and most of the literature on this subject is limited to mass ratios of m* < 2. However, it is known...

Screw propellers create asymmetry around the ship in motion, leading to differences in both side turnings despite the ship having symmetric hull form. A conventional rudder is not expected to contribute to it but a twisted rudder will generate additional asymmetry in the flow and may either balance or increase the difference in both side turnings....

In this paper, the vortex-induced vibration (VIV) response of an elastically mounted rigid circular cylinder is investigated experimentally. An experimental apparatus has designed and mounted over the circulation channel in Ata Nutku Ship Model Testing Laboratory at Istanbul Technical University to investigate the VIV phenomenon on different flow r...

Düşey düzlemde de hareket yeteneğine sahip olan su altı araçlarının manevra problemi aracın yörüngesini tanımlamak için tüm serbestlik derecelerinin matematiksel olarak dikkate alınmasını gerektiren zorlayıcı bir problemdir. Literatürde bu probleme çözüm getiren çalışmalar ağırlıklı olarak aracın derin dalmış durumunu dikkate alırlar. Bu çalışmalar...

This paper presents an investigation into tip effects on vortex induced vibrations (VIV) for circular cylinders. Within this context; the results of the tests, which were carried out in Istanbul Technical University Ata Nutku Circulation Channel, were validated with different studies from the literature. Then, a series of VIV tests were carried out...

Su altı araçları dalmış, şnorkel ve satıh gibi birbirinden çok farklı operasyonel isterlere sahip çeşitli işletme modlarında kullanılabilirler. Dolayısı ile bu araçların hidrodinamik tasarımının birbiri ile çelişen özelliklerin bir arada sağlanmasını gerektiren bir optimizasyon problemi olarak ele alınması gereklidir. Hidrodinamik tasarım konusunun...

In this study, the maneuvering ability of a 1/100 scaled model of Duisburg Test Case (DTC) hull was investigated by utilizing system-based and direct CFD methods. DTC hull has a twisted rudder generating significant asymmetry in the flow, which makes it a specific case for ship maneuvering. Resistance tests were first conducted at Ata Nutku Ship Mo...

The autonomy of any airborne, land borne or waterborne vehicle starts with controlling its speed. To achieve cruise speed control, the conventional approach is to use closed-loop feedback control systems that require high precision sensors. Underwater sensors are expensive due to harsh environment and corrosive properties of seawater. In this study...

Vortex-induced vibrations (VIV) are generally evaluated with relatively simpler two-dimensional (2D) methods using direct numerical simulation (DNS), large eddy simulation (LES) or RANSE-based (Reynolds-Averaged Navier-Stokes Equations) methods. Computationally, these 2D approaches have relatively lower costs which make them more suitable for such...

Despite their high manufacturing cost and structural deficiencies especially in tip regions, highly skewed propellers are preferred in the marine industry, where underwater noise is a significant design criterion. However, hydrodynamic performances should also be considered before a decision to use these propellers is made. This study investigates...

In this study, resistance and propulsion characteristics of the Duisburg Test Case (DTC) Post-Panamax Container Ship were investigated experimentally and numerically. The model scale was different from other studies in the literature. First, resistance experiments with uncertainty analysis were carried out in the Ata Nutku Ship Model Testing Labora...

According to Maritime Traffic Regulations for the Turkish Straits, “steering shall always be by hand” and “automatic steering devices shall never be used”. However, it is considered that recent technological boost in computer science and control engineering opened this regulation to discussion; as today, automatic steering devices are a lot more sa...

Self-propulsion predictions are important to understand propeller-hull interactions and the communication between the main engine and the propulsion system. Experimental work encapsulates the core of self-propulsion estimations, but due to their high cost, initial calculations are made using empirical relations suggested by IMO. However, these empi...

Incompressible flow assumption is an essential step that simplifies numerical simulations for objects inside flowing water. However, incompressibility assumption creates a conflicting situation for sound propagation as the propagation speed is given by c0=dp/dρ where p denotes the pressure and ρ denotes the density. When dρ=0 is assumed to relieve...

As the current trend in the maritime industry is moving toward controlling the ships (either remotely or autonomously); today, the main focus is shifted to the effects of the external disturbances rather than motions in an ideal environment. However, a fundamental part of maneuvering tests is still made in calm water although external disturbances...

The turning circle and zigzag maneuvering performance of surface combatant, DTMB 5415 have been investigated by using system-based method. Unsteady Reynolds averaged Navier Stokes (URANS) approach is utilized to estimate hydrodynamic derivatives and hull-propeller-rudder interactions. DTMB 5415 is a twin-propeller / twin-rudder ship and there are s...

This study aims to propose a fast calculation method to evaluate the total resistance of a traditional ship hull form. It became a common knowledge nowadays that the computational fluid dynamics (CFD) approach is robust in calculating the frictional resistance component of a ship with double body flow solutions. Modeling of the free surface is stil...

Estimation of ship self-propulsion is important for the selection of the propulsion system and the main engine so that the ship can move forward with the required speed. Resistance characteristics of the vessel or the open-water performance of a propeller only are not usually enough to assess the working conditions of the ship. Both in numerical si...

Bir gemiye ait manevra performansını tek bir kriter ile tanımlayabilmek mümkün olmadığı için toplam manevra performansını etkileyen her bir unsur ayrı ayrı ele alınmalıdır. Gemilerin manevra performans tahminlerinin incelendiği bu çalışma iki bölümden oluşmaktadır. Çalışmanın ilk bölümünde literatürde yer alan bazı çalışmalar sınıflandırılarak eksi...

Denizde güvenliği sağlamak ve kirlenmeye yol açabilecek kazaları asgari seviyede tutabilmek amacıyla IMO (International Maritime Organization) tarafından gemilerin manevra kabiliyetleri ile ilgili bazı kriterler belirlenmiştir. Gemilerin manevra performans tahminlerinin incelendiği çalışmanın bu bölümünde IMO'nun belirlemiş olduğu gemi manevra kabi...

Denizaltılar bir donanma için olmazsa olmaz unsurlar olup, savaş durumlarında savaşın kaderini tayin eden kritik sualtı araçlarıdır. Geçen yüzyılda tezahür eden iki dünya savaşının tarihi incelendiğinde, tarafların sahip oldukları deniz teknolojileri arasındaki küçük farklar savaşın kaderini tayin etmiştir. Bu denli küçük teknolojik farklar dahi sa...

Recent developments in Computational Fluid Dynamics (CFD) enabled common access for researchers and thus offers solutions to various complex problems in many different fields. With this motivation, in this study, two kinds of numerical methods were employed to investigate the vertical motions in variable regular waves. While the potential method is...

Vortex induced vibrations (VIV) are highly nonlinear due to three different frequencies involved in the process; fluid force frequency, vortex shedding frequency and oscillation frequency. It is computationally complex to solve such a chaotic fluid flow but recent progress in numerical algorithms, turbulence models and computer capabilities have ma...

zet İnsansız denizaltılar (autonomousunderwatervehicles, AUV) ilerleyen haberleşme ve bilgisayar teknolojileri sayesinde günümüzde oldukça kritik konuma gelmişlerdir. Askeri olarak keşif ve saldırı amaçlı kullanıldıkları gibi, bilimsel çalışmalar için de kullanılmaktadırlar. Küçük olmalarının yanında büyük ebatlardaki hemcinslerinde bulunan gürültü...

In this study, a rigid grid strategy is adopted to obtain non-dimensional forces and moments of various KVLCC2 models in different scales. A wide variety of experimental results exist in the literature and the results generated in this study utilizing the rigid grid are compared with the results obtained with the overset grid approach given in a re...

Body motions inside fluid flow are usually modeled using deforming grids. As the body moves, the mesh elements modeling the fluid domain deform or remesh at each time step. However, these deformations of the elements are rather uncontrolled and may lead to low quality mesh which would return unphysical results if the body is doing significant motio...

The prediction of wave resistance in naval architecture is an important aspect especially at high Froude numbers where a great percentage of total resistance of ships and submerged bodies is caused by waves. In addition, during hull form optimization, wave resistance characteristics of a ship must closely be observed. There are potential, viscous a...

Research on vortex-induced vibrations (VIV) mainly involves experimental science but building laboratory setups to investigate the flow are expensive and time consuming. Computational fluid dynamics (CFD) methods may offer a faster and a cheaper way to understand this phenomenon depending on the solution approach to the problem. The context of this...

In this paper, the performance of 2D (two-dimensional) foils moving with a constant speed above a free water surface has been investigated by an Iterative Boundary Element Method (IBEM). Not only the proximity heights of the foil to the free surface but also the moving speeds of the foil can affect substantially the foil characteristics, such as; p...

Seakeeping is a very complex problem in Maritime problems involving at least 3 degree-of-freedom (3-DOF) motion of the hull and until commercialized CFD softwares became widely used, the problem was approached by linear approaching applying potential theory. With this motivation, two kinds of numerical methods are employed to study the vertical mot...

Vortex-induced vibrations (VIV) are highly nonlinear and it is hard to approach the problem analytically or computationally. Experimental investigation is therefore essential to address the problem and reveal some physical aspects of VIV. Although computational fluid dynamics (CFD) offers powerful methods to generate solutions, it cannot replace ex...

Aircraft flying close to the ground benefit from enhanced efficiency owing to decreased induced drag and increased lift. In this study, a mathematical model is developed to simulate the takeoff of a wing near the ground using an Iterative Boundary Element Method (IBEM) and the finite difference scheme. Two stand-alone sub-codes and a mother code, w...

This paper discusses the effects of the free surface and the propeller on a benchmark Post-Panamax Ship, Duisburg Test Case (DTC). The experimental results are already available in the literature. The computational study carried out in this work is verified first with the experiments and then used to explain some of the physical aspects associated...

Referans çalışmalar nümerik metotların doğrulanmasını sağlayan en temel ve yaygın çalışmalardır. S175, Kriso Container Ship (KCS), Duisburg Test Case (DTC) ve Hamburg Test Case (HTC) gibi referans çalışmaların geometrileri ve deney ölçüm değerleri literatürde mevcuttur. Bu referans çalışmalardan elde edilen değerler yapılan simülasyonların hata ve...

In the Marine Renewable Energy Laboratory (MRELab) of the University of Michigan, Flow Induced Motion (FIM) is studied as a means to convert marine hydrokinetic energy to electricity using the VIVACE energy harvester [1-4]. Turbulence stimulation in the form of sand-strips, referred to as Passive Turbulence Control (PTC), were added to oscillating...

Understanding the effects of the parameters affecting the interaction of tandem hydrofoil system is a crucial subject in order to fully comprehend the aero/hydrodynamics of any vehicle moving inside a fluid. This study covers a parametric study on tandem hydrofoil interaction in both potential and viscous fluids using iterative Boundary Element Met...

The prediction of resistance of ships and submerged bodies is an important aspect in naval architecture. Total resistance of a floating body can be decomposed into viscous and wave resistance components. There are potential, viscous and experimental methods to determine the resistance components of a ship. RANSE (Reynolds Averaged Navier Stokes Equ...

In this paper, an iterative boundary element method (IBEM) was proposed to solve for a wing-in-ground (WIG) effect. IBEM is a fast and accurate method used in many different fields of engineering and in this work; it is applied to a fluid flow problem assessing a wing in ground proximity. The theory and the developed code are validated first with o...

WIG vehicles have gained ground in the last decade due to bureaucratic and technological barriers lifted thanks to the developments in the control engineering. These crafts can offer an economical transportation over the sea with their natural ability to use air like a cushion but there is still some enhancement to be made in terms of their efficie...

Blasius equation describes the boundary layer formed over a flat plate inside a fluid and this equation is solved numerically by the method of moments which is a type of weighted residual methods. Compared to the tradition-ally used Runge – Kutta Method, Method of Moments propose a direct solution to Blasius Equation which makes it easier to solve....

The propeller performance has been investigated using a benchmark Duisburg Test Case ship with RANSE. First, the hydrodynamic characteristics of propeller in case of open water have been analyzed by a commercial CFD program and the results are compared with those of experimental data. Later, the flow around the bare hull has been solved and the fri...

Ülkemizde yüksek hızlı teknelerle ilgili yapılmış bazı çalışmalar olmasına rağmen bunlar yeterli sayıda değildir. Bu tip teknelerin teorilerinin tam olarak anlaşılmamasından dolayı bu teknelere karşı ilgi fazla olmamış dolayısıyla gemi inşa sanayimiz de bu alanın içerisine fazla girmemiştir. Yüksek hızlı teknelerden olan hidrofoil tekneler temelde...

Su altında seyreden yapıların veya hidrodinamik destek sağlayan takıntıların serbest su yüzeyinde oluşturduğu dalga profili ve serbest su yüzeyinin hidrofoil üzerindeki kaldırma kuvveti katsayısına etkileri son yıllarda sıkça araştırma konusu olmuştur. Bu çalışmada çeşitli derinliklerdeki hidrofoilin etrafındaki akış sayısal olarak incelenmiştir. B...

Tandem hydrofoil system is used even in the most ordinary ships; the hydrofoil that confronts the flow first represents the ship section, while the other hydrofoil stands for the rudder section. This study covers a parametric study on tandem hydrofoil interaction including variations of distance, thickness, angle of attack and chord length of hydro...

A direct and an iterative boundary element method using source distributions to represent the body are applied to calculate the pressure distribution on symmetric NACA airfoils. First, the effects of the foils on each other are examined. Then, the two methods are compared in terms of the solutions they generate and the time consumed. The calculatio...

The aim of this study is to mathematically model Bodrum type gulet vessels' series, starting from a working vessel with a good performance in all aspects of seakeeping. Considering the fact that only one vessel is insufficient in building up a series form, some other similar (to main vessel) vessels weregenerated with One Minus Prismatic Coefficien...