mehmet Atlar | University of Strathclyde, Glasgow (original) (raw)

Papers by mehmet Atlar

Ocean Engineering, 2003

A practical, low order and potential-based surface panel method is presented to predict the flow ... more A practical, low order and potential-based surface panel method is presented to predict the flow around a three-dimensional rectangular foil section including the effect of boundary layer. The method is based on a boundary-integral formulation, known as the “Morino formulation” and the boundary layer effect is taken into account through a complementary thin boundary layer model. The numerical approach used

Proceedings of the …, 2001

This study presents the results of cavitation tunnel tests carried out with model propeller of a ... more This study presents the results of cavitation tunnel tests carried out with model propeller of a Fisheries Research Vessel (FRV) and those of noise measurements with its full-scale propeller to validate the low-noise performance of this propeller. The tests involve the simulation of ...

Ocean Engineering

This paper presents the results of a numerical performance analysis to demonstrate the worthiness... more This paper presents the results of a numerical performance analysis to demonstrate the worthiness of a recently patented new concept propulsor, the so-called “thrust-balanced propeller (TBP)”. The main advantage of this unconventional propulsor is its inherent ability to reduce the unsteady effect of blade forces and moments when it is operating in a non-uniform wake flow. The propulsor comprises a pair of diametrically opposed blades that are connected to one another and mounted so as to be rotatable together through a limited angle about their spindle axis. A quasi-hydrodynamic approach is described and applied to perform the numerical analysis using a state-of-the-art lifting surface procedure for conventional propellers. Performance comparisons with a conventional fixed-pitch propeller are made for the blade forces and moments, efficiency, cavitation extents and fluctuating hull pressures. Bearing in mind the quasi-static nature of the analyses, the results present favourable pe...

Ocean Engineering, 2001

A surface panel method is employed for the thin boundary layer calculation of heavily loaded mari... more A surface panel method is employed for the thin boundary layer calculation of heavily loaded marine propellers in steady state conditions. Employing the surface panel method, known as the Morino Method, the flow field around the propeller is represented by an unknown ...

Biofilms are recognized as unwanted microfouling settlements which can increase frictional drag b... more Biofilms are recognized as unwanted microfouling settlements which can increase frictional drag by up to 10% or more and subsequently reduce the efficiency of ships and other moving marine structures such as tidal turbines. Generally, assessing the impacts of macrofouling (weed/barnacle) on antifouling paint performance is easier than for microfouling. This is due to the heterogeneous structure and dynamic properties of biofilms, and the difficulty of simulation and assessment regarding surface roughness and frictional force. This research aims to investigate the effects of Foul-Release (FR) coatings on ship performance with a focus on the impacts of marine biofilms. For this purpose, the Emerson Cavitation Tunnel (ECT) research team designed a biofilm cultivation tank to allow the growth of fresh water biofilm under dynamic conditions on circular test cylinders. Before and after growth of biofilms on these cylinders, roughness measurements were conducted for aluminium cylinders coated with two foul-release commercial paints, along with one control aluminium reference surface, using a portable laser profilometer device. Moreover, the behaviour and effects of biofilms on frictional drag characteristics of different FR coating surfaces was assessed using the torpedo shaped axisymmetric test body of the ECT. Assessments have shown that biofilm chamber can be successfully used for only biofilm growth on target surfaces and avoiding possibility of biofilm to evolve to macrofouling species. The tests and subsequent analysis indicated that these two FR coatings have very low surface roughness values, and good antifouling performance when even covered with heavy biofilm. Further research is underway to investigate this.

This paper presents the results of towing tank tests carried out to predict the wave loads in reg... more This paper presents the results of towing tank tests carried out to predict the wave loads in regular wave conditions on a Deep-V hull form catamaran model. The experiments were carried out at the Newcastle University towing tank using a segmented model of the university’s new research vessel, “The Princess Royal”. The vessel is a twin hull with a Deep-V shape cross-section. The model, divided into two parts at the cross-deck level, was fitted with a 5-axis load cell at the position of the vessel’s centre of gravity in order to measure the motions response and wave loads due to the encountered waves. The longitudinal, side and vertical forces, along with the prying and yaw splitting moments were measured. The results obtained were further compared with those from numerical predictions carried out using a 3D panel method code based on potential flow theory that uses Green’s Function with the forward speed correction in the frequency domain. The results highlight reasonable correlations between the measurements and the predictions as well as the need for a proper understanding of the response of the multihull vessels to the wave-induced loads due to the non-linearity that have been observed in the experimental measurements of wave loads.

Biofouling, Oct 21, 2018

There are limited scientific data on contributors to the added drag of in-service ships, represen... more There are limited scientific data on contributors to the added drag of in-service ships, represented by modern-day coating roughness and biofouling, either separately or combined. This study aimed to gain an insight into roughness and hydrodynamic performance of typical coatings under in-service conditions of roughened ships' hull surfaces. Comprehensive and systematic experimental data on the boundary layer and drag characteristics of antifouling coating systems with different finishes are presented. The coating types investigated were linear-polishing polymers, foul-release and controlled-depletion polymers. The data were collected through state-of-the-art equipment, including a 2-D laser Doppler velocimetry (LDV) system for hydrodynamic data in a large circulating water tunnel. Three coating systems were first applied on flat test panels with 'normal' finishes in the first test campaign to represent coating applications under idealised laboratory conditions. In order to address more realistic roughness conditions, as typically observed on ships' hulls, 'low' and 'high' roughness densities were introduced into the same types of coating, in the second test campaign. The data collected from the first test campaign served as the baseline to demonstrate the effect on the surface roughness and hydrodynamic drag characteristics of these coating types as a result of 'in-service' or 'severely flawed' coating application scenarios. Data collected on coatings with a range of in-service surface conditions provided a basis to establish correlation between the surface roughness characteristics and hydrodynamic performance (roughness function). The findings of the study indicate that the estimations of drag penalties based on well-applied, relatively smooth coating conditions underestimate the importance of hull roughness, which although undesirable, is commonplace in the world's commercial fleet.

The paper presents numerical results obtained by solving the two-dimensional radiation and diffra... more The paper presents numerical results obtained by solving the two-dimensional radiation and diffraction problems associated with single and twin-hulled SWATH-type sections in and below the free surface. The influence of tilt on the motion-induced and wave-induced coefficients of circular and rectangular, hull and hull-strut combinations in the in-plane modes of motion and beam seas, is examined. Interference in the upright condition is discussed. The conclusions provide guidance as to the importance of both effects in the estimation of the hydrodynamic characteristics of twin-hulled ships. .

Ocean Engineering, Sep 1, 2016

The aim of this research is to reduce Carbon Dioxide emission through enhanced propeller selectio... more The aim of this research is to reduce Carbon Dioxide emission through enhanced propeller selection achieved by a more realistic identification of the true propeller operating point. By recognising that the 'dead-ahead steady speed in flat calm water' condition is not representative of the true operation of a ship in a seaway, a new paradigm is proposed. By taking into consideration the effects of wind and waves on the ship's true speed through the water and thus the probable load condition of the propeller, throughout the ship's mission, a probable propeller operating condition is identified. Propellers are then selected for both the original condition and the adapted condition, and their performance compared using time-domain mission simulations. The objective of the study is to demonstrate how the alternative propeller selection methodologies proposed, can on average provide greater overall efficiency. Results from the case studies are encouraging, with a gain of 2.34% in open water propeller efficiency for a 3600 Twenty foot Equivalent Unit container ship, equating to a saving of 3.22% in Carbon Dioxide emissions.

海洋環境安全學會誌 = Journal of the Korean society of marine environment & safety, Aug 31, 2013

Journal of Cleaner Production, Aug 1, 2023

Measurements in the Fully Turbulent Flow Channel (FTFC) are presented for Reynolds number up to 3... more Measurements in the Fully Turbulent Flow Channel (FTFC) are presented for Reynolds number up to 3.3•10 5 , based on the mean bulk velocity and the channel height. The FTFC is a new experimental facility recently installed at the Department of Naval Architecture, Ocean and Marine Engineering of the University of Strathclyde. It is a high aspect ratio flow channel with a three-meter-long testing section, designed for the indirect measurement of the drag caused by surface characteristics. The main advantage of this channel is that the measurements of the pressure drop along the test section can be combined with laser-based boundary layer measurement techniques such as LDA, PIV, etc. The present work focuses on the design features and the calibration of the new experimental facility, with hydraulically smooth control panels produced on purpose. The interest in these data originates from the fact that channel flow serves as a reference flow for varying special surface structures, such as fouling control coatings, as well as some drag reduction mechanisms such as riblets, dimples, tubercles, in the presence of some biofouling types.

Although landing craft are not sophisticated vessels, their functional/operational requirements o... more Although landing craft are not sophisticated vessels, their functional/operational requirements often result in a hull shape which may encounter unusual hydrodynamic phenomena, requiring remedial attention. One such instance is discussed in this paper, which presents hull form solutions adopted to address excessive vibration experienced on-board an enhanced landing craft operating in the Arabian Gulf region. Through Computational Fluid Dynamics (CFD) simulations, the sources of excessive vibration experienced by this vessel were identified. The sources included the current bow design, which promoted aeration; an extensive flat bottom, which channelled the air to a shallow buttock-flow stern region; angled pram type stern fitted with blunt-ended appendages generated a non-uniform flow that was too severe for the existing propeller-hull clearances. The combination of these unfavourable flow conditions with the cavitating propellers resulted in undesirable Propeller-Hull Vortex Cavitation (PHVC) which manifested itself with excessive aft end vibrations and noise. To remedy the situation and to control the excessive vibrations, further CFD simulations guided the necessary hull form modifications. The identified countermeasures included anti-Propeller Hull Vortex (PHV) plates and streamlining of stern appendages. Subsequent sea trials showed horizontal vibration levels were reduced by 85%, which significantly improved the conditions on-board. This paper presents a technical summary of the above countermeasures, their implementations on the vessel, which included full-scale trials to measure the speed-power performance, hull vibrations and cavitation observations using a borescope system, and discussions of the results of these countermeasures. The paper concludes with an outline proposal for further design study, which could reduce on-board vibrations even further as well as providing other operational benefits regarding propulsive efficiency and manoeuvrability using the recently developed "Gate Rudder System ®" as a novel Energy Saving Device (ESD).

Proceedings of the International Conference on Port and Ocean Engineering Under Arctic Conditions, 2007

Propeller ice interaction is a complex phenomenon that relies on innovative and complex experimen... more Propeller ice interaction is a complex phenomenon that relies on innovative and complex experimental research. This paper reports on tests performed in the Emerson Cavitation Tunnel (ECT) examining effect of performance of an ice class propulsor in blocked flow and introduces a novel set of ice milling experiments. The findings reported herein are part of a PhD study into the phenomenon and represent the early analysis of the findings; further analysis is ongoing to better understand the phenomena.

Ocean Engineering, Dec 1, 2022