Anti-slamming bulbous bow and tunnel stern applications on a novel Deep-V catamaran for improved performance

Atlar, Mehmet,Seo, Kwangcheol,Sampson, Roderick,Danisman, Devrim Bulent The Society of Naval Architects of Korea 2013 International Journal of Naval Architecture and Oc Vol.5 No.2

While displacement type Deep-V mono hulls have superior seakeeping behaviour at speed, catamarans typically have modest behaviour in rough seas. It is therefore a logical progression to combine the superior seakeeping performance of a displacement type Deep-V mono-hull with the high-speed benefits of a catamaran to take the advantages of both hull forms. The displacement Deep-V catamaran concept was developed in Newcastle University and Newcastle University's own multi-purpose research vessel, which was launched in 2011, pushed the design envelope still further with the successful adoption of a novel anti-slamming bulbous bow and tunnel stern for improved efficiency. This paper presents the hullform development of this unique vessel to understand the contribution of the novel bow and stern features on the performance of the Deep-V catamaran. The study is also a further validation of the hull resistance by using advanced numerical analysis methods in conjunction with the model test. An assessment of the numerical predictions of the hull resistance is also made against physical model test results and shows a good agreement between them.

EMERSON CAVITATION TUNNEL GROUP OF NEWCASTLE UNIVERSITY, UK

Mehmet Atlar,Kwangcheol Seo 대한조선학회 2011 大韓造船學會誌 Vol.48 No.4

The School of Marine Science and Technology (MAST) of Newcastle University is the largest and broadest based marine school in Europe if it is not in the world. With a total of 900 students located in three different sites and supported by 90 members of academic and technical staff, MAST have an approximate 9M GBP current turnover. The School is complemented by excellent range of and unique experimental and full-scale marine testing facilities. This includes 63 years old and currently the UK’s only active propeller cavitation tunnel, The Emerson Cavitation tunnel (ECT) which is supported by the dedicated research and development group, The Emerson Cavitation Tunnel Group (ECTG). This paper highlights the activities of ECTG and their contribution in the research and development activities of MAST as well as the teaching and consultancy with a focus on the recent, past and current activities.

Anti-slamming bulbous bow and tunnel stern applications on a novel Deep-V catamaran for improved performance

Mehmet Atlar,성광철,Roderick Sampson,Devrim Bulent Danisman 대한조선학회 2013 International Journal of Naval Architecture and Oc Vol.5 No.2

While displacement type Deep-V mono hulls have superior seakeeping behaviour at speed, catamarans typically have modest behaviour in rough seas. It is therefore a logical progression to combine the superior seakeeping performance of a displacement type Deep-V mono-hull with the high-speed benefits of a catamaran to take the advantages of both hull forms. The displacement Deep-V catamaran concept was developed in Newcastle University and Newcastle University’s own multi-purpose research vessel, which was launched in 2011, pushed the design envelope still further with the successful adoption of a novel anti-slamming bulbous bow and tunnel stern for improved efficiency. This paper presents the hullform development of this unique vessel to understand the contribution of the novel bow and stern features on the performance of the Deep-V catamaran. The study is also a further validation of the hull resistance by using advanced numerical analysis methods in conjunction with the model test. An assessment of the numerical predictions of the hull resistance is also made against physical model test results and shows a good agreement between them.

An experimental investigation into cavitation behaviour and pressure characteristics of alternative blade sections for propellers

Korkut, Emin,Atlar, Mehmet,Wang, Dazheng The Society of Naval Architects of Korea 2013 International Journal of Naval Architecture and Oc Vol.5 No.1

During the final quarter of the last century considerable efforts have been spent to reduce the hull pressure fluctuations caused by unsteady propeller cavitation. This has resulted in further changes in propeller design characteristics including increased skew, tip unloading and introduction of "New Blade Sections" (NBS) designed on the basis of the so-called Eppler code. An experimental study was carried out to investigate flow characteristics of alternative two-dimensional (2-D) blade sections of rectangular planform, one of which was the New Blade Section (NBS) developed in Newcastle University and other was based on the well-known National Advisory Committee for Aeronautics (NACA) section. The experiments comprised the cavitation observations and the measurements of the local velocity distribution around the blade sections by using a 2-D Laser Doppler Anemometry (LDA) system. Analysis of the cavitation tests demonstrated that the two blade sections presented very similar bucket shapes with virtually no width at the bottom but relatively favourable buckets arms at the suction and pressure sides for the NACA section. Similarly, pressure analysis of the sections displayed a slightly larger value for the NBS pressure peak. The comparative overall pressure distributions around the sections suggested that the NBS might be more susceptible to cavitation than the NACA section. This can be closely related to the fundamental shape of the NBS with very fine leading edge. Therefore a further investigation into the modification of the leading edge should be considered to improve the cavitation behaviour of the NBS.

Performance prediction of horizontal axis marine current turbines

Bal, Sakir,Atlar, Mehmet,Usar, Deniz Techno-Press 2015 Ocean systems engineering Vol.5 No.2

In this study, hydrodynamic performance of a 400 mm diameter horizontal axis marine current turbine model was tested in a cavitation tunnel with 1.21 m x 0.8 m cross-section for over a range of tip speed ratios. Torque and thrust data, as well as cavitation visualizations, for certain operating conditions were acquired. Experimental results indicated that the turbine can be exposed to significant amount of sheet and cloud cavitation over the blades along with vortex cavitation at the blade tips. Inception and distribution of cavitation along the blades of the model turbine were then modelled numerically for design operating conditions using a vortex lattice method. The method was also applied to a turbine tested previously and obtained results were compared with the data available. The comparison between simulation results and experimental data showed a slight difference in terms of span-wise extent of the cavitation region. The cloud and tip vortex cavity observed in experiments cannot be modelled due to the fact that the VLM lacks the ability to predict such types of cavitation. Notwithstanding, the use of such prediction methods can provide a reasonably accurate approach to estimate, therefore take the hydrodynamic effects of cavitation into account in design and analysis of marine current turbines.

An experimental investigation into cavitation behaviour and pressure characteristics of alternative blade sections for propellers

Emin Korkut,Mehmet Atlar,Dazheng Wang 대한조선학회 2013 International Journal of Naval Architecture and Oc Vol.5 No.1

During the final quarter of the last century considerable efforts have been spent to reduce the hull pressure fluctuations caused by unsteady propeller cavitation. This has resulted in further changes in propeller design characteristics including increased skew, tip unloading and introduction of “New Blade Sections” (NBS) designed on the basis of the so-called Eppler code. An experimental study was carried out to investigate flow characteristics of alternative two-dimensional (2-D) blade sections of rectangular planform, one of which was the New Blade Section (NBS) developed in Newcastle University and other was based on the well-known National Advisory Committee for Aeronautics (NACA) section. The experiments comprised the cavitation observations and the measurements of the local velocity distribution around the blade sections by using a 2-D Laser Doppler Anemometry (LDA) system. Analysis of the cavitation tests demonstrated that the two blade sections presented very similar bucket shapes with virtually no width at the bottom but relatively favourable buckets arms at the suction and pressure sides for the NACA section. Similarly, pressure analysis of the sections displayed a slightly larger value for the NBS pressure peak. The comparative overall pressure distributions around the sections suggested that the NBS might be more susceptible to cavitation than the NACA section. This can be closely related to the fundamental shape of the NBS with very fine leading edge. Therefore a further investigation into the modification of the leading edge should be considered to improve the cavitation behaviour of the NBS.

Experimental investigation of dynamic trim control devices in fast speed vessel

Kwang-Cheol Seo,Nithin Gopakumar,Mehmet Atlar 한국항해항만학회 2013 한국항해항만학회지 Vol.37 No.2

The displacement Deep-V catamaran concept was developed in Newcastle University(UNEW) through development of the systematic Deep-V catamaran series. One of the most important Deep-V catamaran launched to date is Newcastle University’s own multi-purpose research vessel, The Princess Royal. The vessel was launched in 2011 and enhanced the Deep-V catamaran concept further with the successful adoption of a novel anti-slamming bulbous bow and tunnel stern for improved efficiency. It was however identified that the vessel has substantial amount of dynamic trim that limited the visibility of the captain. The dynamic trim also increased the wave-making resistance thereby preventing the vessel from attaining its maximum speed in certain sea states. This paper therefore presents the application of devices such as Trim Tabs, Interceptors, Transom Wedges and Integrated Transom Wedges-Tabs to control the dynamic trim and improvement of fuel efficiency of the vessel. All of these energy saving devices were fitted into a model for tests in Newcastle University’s Towing Tank. Model test verification confirmed that the optimum appendage was the interceptors, they produced a 5 % power saving and 1.2 degree trim reduction at 15 knots, and investigations of full scale trials will be scheduled with and without application of device to compare the improvement of performance.

“Inclined Keel” 컨테이너선의 조파저항 최소화를 위한 선형최적화

서광철(Kwang-Cheol Seo),Mehmet Atlar,김희정(Hee-Jung Kim),전호환(Ho-Hwan Chun) 대한조선학회 2009 大韓造船學會 論文集 Vol.46 No.2

“Inclined Keel”을 이용한 컨테이너선의 추진효율 향상

서광철(Kwang-Cheol Seo),Mehmet Atlar,김희정(Hee-Jung Kim),전호환(Ho-Hwan Chun),강대수(Dae-Soo Kang) 대한조선학회 2007 大韓造船學會 論文集 Vol.44 No.4

Experimental investigation of dynamic trim control devices in fast speed vessel

Seo, Kwang-Cheol,Gopakumar, Nithin,Atlar, Mehmet Korean Institute of Navigation and Port Research 2013 한국항해항만학회지 Vol.37 No.2

The displacement Deep-V catamaran concept was developed in Newcastle University(UNEW) through development of the systematic Deep-V catamaran series. One of the most important Deep-V catamaran launched to date is Newcastle University's own multi-purpose research vessel, The Princess Royal. The vessel was launched in 2011 and enhanced the Deep-V catamaran concept further with the successful adoption of a novel anti-slamming bulbous bow and tunnel stern for improved efficiency. It was however identified that the vessel has substantial amount of dynamic trim that limited the visibility of the captain. The dynamic trim also increased the wave-making resistance thereby preventing the vessel from attaining its maximum speed in certain sea states. This paper therefore presents the application of devices such as Trim Tabs, Interceptors, Transom Wedges and Integrated Transom Wedges-Tabs to control the dynamic trim and improvement of fuel efficiency of the vessel. All of these energy saving devices were fitted into a model for tests in Newcastle University's Towing Tank. Model test verification confirmed that the optimum appendage was the interceptors, they produced a 5% power saving and 1.2 degree trim reduction at 15 knots, and investigations of full scale trials will be scheduled with and without application of device to compare the improvement of performance.