Pub Date : 2023-09-11DOI: 10.1177/14750902231197886
Andrea Farkas, Nastia Degiuli, Ivan Tomljenović, Ivana Martić
Due to interference effects, the resistance of a catamaran is not the same as the double resistance of the monohull. If demihulls are close enough to each other, the wave fields generated by each demihull usually significantly interfere causing either advantageous or disadvantageous effects. In this paper, the numerical investigation of interference effects for the Delft 372 catamaran is performed. The verification and validation studies are performed demonstrating the potential of the proposed numerical model for the analysis of interference effects. The investigation of the effect of Froude number and demihull separation on the total resistance of a catamaran, trim angle, and sinkage is conducted. The interference effects are quantified through the interference factor, which is defined based on the total resistance of a catamaran and double the total resistance of the monohull. Finally, the flow field characteristics, wave patterns, and pressure distributions are analysed using Computational Fluid Dynamics.
{"title":"Numerical investigation of interference effects for the Delft 372 catamaran","authors":"Andrea Farkas, Nastia Degiuli, Ivan Tomljenović, Ivana Martić","doi":"10.1177/14750902231197886","DOIUrl":"https://doi.org/10.1177/14750902231197886","url":null,"abstract":"Due to interference effects, the resistance of a catamaran is not the same as the double resistance of the monohull. If demihulls are close enough to each other, the wave fields generated by each demihull usually significantly interfere causing either advantageous or disadvantageous effects. In this paper, the numerical investigation of interference effects for the Delft 372 catamaran is performed. The verification and validation studies are performed demonstrating the potential of the proposed numerical model for the analysis of interference effects. The investigation of the effect of Froude number and demihull separation on the total resistance of a catamaran, trim angle, and sinkage is conducted. The interference effects are quantified through the interference factor, which is defined based on the total resistance of a catamaran and double the total resistance of the monohull. Finally, the flow field characteristics, wave patterns, and pressure distributions are analysed using Computational Fluid Dynamics.","PeriodicalId":20667,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135980867","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-08DOI: 10.1177/14750902231196812
Marten Hollm, L. Dostal, John D Carter, R. Seifried
The hydrodynamic forces of nonlinear deep water gravity waves acting on cylindrical offshore structures are studied. Thereby, the waves are excited by random wind and the corresponding effect on the particle paths and hydrodynamic forces is investigated. This is done for the Peregrine breather solution of the nonlinear Schrödinger equation, which is nowadays considered as a prototype of extreme waves in open seas. Using this theory, the loads on mechanical structures can be calculated efficiently. It is shown that the Peregrine breather can exist under strong and gusty wind conditions and the water particles experience a horizontal drift. This leads to a force with randomly increasing amplitude in time, whereby a mean wind velocity of 50 km/h results in an increase of about 3%. The increase of hydrodynamic forces caused by the wind should therefore be considered for the construction of mechanical structures operating in the ocean.
{"title":"Determination of particle paths and hydrodynamic forces of random wind forced nonlinear ocean waves","authors":"Marten Hollm, L. Dostal, John D Carter, R. Seifried","doi":"10.1177/14750902231196812","DOIUrl":"https://doi.org/10.1177/14750902231196812","url":null,"abstract":"The hydrodynamic forces of nonlinear deep water gravity waves acting on cylindrical offshore structures are studied. Thereby, the waves are excited by random wind and the corresponding effect on the particle paths and hydrodynamic forces is investigated. This is done for the Peregrine breather solution of the nonlinear Schrödinger equation, which is nowadays considered as a prototype of extreme waves in open seas. Using this theory, the loads on mechanical structures can be calculated efficiently. It is shown that the Peregrine breather can exist under strong and gusty wind conditions and the water particles experience a horizontal drift. This leads to a force with randomly increasing amplitude in time, whereby a mean wind velocity of 50 km/h results in an increase of about 3%. The increase of hydrodynamic forces caused by the wind should therefore be considered for the construction of mechanical structures operating in the ocean.","PeriodicalId":20667,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment","volume":"21 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2023-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86495533","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-05DOI: 10.1177/14750902231192145
Fei Qi, Tian-zheng Wang, Xiaohang Wang, Lisu Chen
Challenges exist in the power generation efficiency and safety of marine current turbines (MCTs), as the MCT blades are often attached by foreign objects when operating underwater. It is essential for the stable operation of an MCT to recognize attachments timely and accurately. However, underwater imaging suffers from blurry edges due to light attenuation and scattering. It is challenging for accurate recognition through underwater images since blurry edges result in unclear edge features. To alleviate this problem, LAW-IFF Net is proposed in this paper, which mainly contains two parts. Firstly, this paper proposes to transform the local averages of feature maps into weight matrices, namely the locally average weighting (LAW) mechanism. It is intended to alleviate the edge gradient reduction caused by blurry edges. Secondly, the proposed improved feature fusion (IFF) mechanism aims to overcome the deviation caused by the feature fusion of different attention branches based on spatial attention. At the same time, the lightweight networks are combined with the proposed method to improve the computation speed and ensure the timeliness of recognition. Experimental results on the MCT dataset show the superiority of the proposed method in terms of accuracy and speed of attachment recognition in images with blurry edges. The experimental results on publicly available datasets show the applicability of the proposed method to other underwater images.
{"title":"LAW-IFF Net: A semantic segmentation method for recognition of marine current turbine blade attachments under blurry edges","authors":"Fei Qi, Tian-zheng Wang, Xiaohang Wang, Lisu Chen","doi":"10.1177/14750902231192145","DOIUrl":"https://doi.org/10.1177/14750902231192145","url":null,"abstract":"Challenges exist in the power generation efficiency and safety of marine current turbines (MCTs), as the MCT blades are often attached by foreign objects when operating underwater. It is essential for the stable operation of an MCT to recognize attachments timely and accurately. However, underwater imaging suffers from blurry edges due to light attenuation and scattering. It is challenging for accurate recognition through underwater images since blurry edges result in unclear edge features. To alleviate this problem, LAW-IFF Net is proposed in this paper, which mainly contains two parts. Firstly, this paper proposes to transform the local averages of feature maps into weight matrices, namely the locally average weighting (LAW) mechanism. It is intended to alleviate the edge gradient reduction caused by blurry edges. Secondly, the proposed improved feature fusion (IFF) mechanism aims to overcome the deviation caused by the feature fusion of different attention branches based on spatial attention. At the same time, the lightweight networks are combined with the proposed method to improve the computation speed and ensure the timeliness of recognition. Experimental results on the MCT dataset show the superiority of the proposed method in terms of accuracy and speed of attachment recognition in images with blurry edges. The experimental results on publicly available datasets show the applicability of the proposed method to other underwater images.","PeriodicalId":20667,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment","volume":"5 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2023-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75151303","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-08-30DOI: 10.1177/14750902231194794
Köksal Çolak, H. Ölmez, Betul Sarac
In this study, the applicability, fuel saving and CO2 emission reducing potential of the triple heat-exchanger fed by the diesel generator exhaust gas with and without water steam have been studied for ship’s one and two main engines pre-heating and freshwater generation (FWG) cycles under port conditions with conducting energy and exergy analysis. The performance criteria (PC) and exergy efficiency (ε) values of the main engine pre-heating and freshwater generator systems of the Ro-Ro ship selected for the case study were determined by written Matlab 2021a codes merging CoolProp 6.4.2 database with Python. It was determined that even at the lowest operating load of the diesel generator (25%), the exhaust heat energy would be sufficient to preheat the main engine and generating fresh water with also saving fuel consumption. As a result, during the 12-h port period, each 1 kW heat energy reduction on steam will provide 0.0853 kg/h fuel saving in the boiler. Thus, 273 kg CO2 emission will be reduced for each kW of heat energy to be obtained. Considering the comparatively increased PC and ε values of whole system cycle containing common triple heat-exchanger for two main engines, it can be used conveniently and reliably on ships.
{"title":"Waste heat recovery assessment of triple heat-exchanger usage for ship main engine pre-heating and fresh water generation systems","authors":"Köksal Çolak, H. Ölmez, Betul Sarac","doi":"10.1177/14750902231194794","DOIUrl":"https://doi.org/10.1177/14750902231194794","url":null,"abstract":"In this study, the applicability, fuel saving and CO2 emission reducing potential of the triple heat-exchanger fed by the diesel generator exhaust gas with and without water steam have been studied for ship’s one and two main engines pre-heating and freshwater generation (FWG) cycles under port conditions with conducting energy and exergy analysis. The performance criteria (PC) and exergy efficiency (ε) values of the main engine pre-heating and freshwater generator systems of the Ro-Ro ship selected for the case study were determined by written Matlab 2021a codes merging CoolProp 6.4.2 database with Python. It was determined that even at the lowest operating load of the diesel generator (25%), the exhaust heat energy would be sufficient to preheat the main engine and generating fresh water with also saving fuel consumption. As a result, during the 12-h port period, each 1 kW heat energy reduction on steam will provide 0.0853 kg/h fuel saving in the boiler. Thus, 273 kg CO2 emission will be reduced for each kW of heat energy to be obtained. Considering the comparatively increased PC and ε values of whole system cycle containing common triple heat-exchanger for two main engines, it can be used conveniently and reliably on ships.","PeriodicalId":20667,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment","volume":"31 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2023-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72528046","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-08-29DOI: 10.1177/14750902231194703
Murat Mert Tekeli, Elİf Bal BeşİkÇİ, Muhammet Gul, E. Akyuz, O. Arslan
There are a wide range of chemical cargoes carried in chemical tankers. The chemical tankers are carrying hazardous chemical cargoes in their cargo tanks. When carrying hazardous chemicals in cargo tanks, the coating is required which is to provide safety barrier between the hull plate and the cargo. Therefore, capabilities of cargo tanks are of paramount importance for safe and efficient transport. Tank coatings to be applied to chemical tankers are epoxy coatings, zinc silicate coating, stainless steel coating, and marine line coating. This paper aims at conducting a numerical performance analysis of tank coatings in chemical tankers to contribute decision-making process of shipowner and safety professionals. To achieve this purpose, a multi-criterion decision-making (MCDM) tool is adopted: An Analytical Hierarchy Process (AHP) and Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) under interval type-2 fuzzy set (IT2Fs) environment. The outcomes of the numerical performance analysis showed that stainless steel type tank coating has the best performance since result of closeness coefficient value c( xj) is found 0.55. The findings of the research will contribute chemical tanker ship owners, safety inspectors, naval architects, and safety professionals during decision-making process of ideal cargo tank coating.
{"title":"Application of IT2Fs-AHP and TOPSIS modeling for performance analysis of tank coatings in chemical tankers","authors":"Murat Mert Tekeli, Elİf Bal BeşİkÇİ, Muhammet Gul, E. Akyuz, O. Arslan","doi":"10.1177/14750902231194703","DOIUrl":"https://doi.org/10.1177/14750902231194703","url":null,"abstract":"There are a wide range of chemical cargoes carried in chemical tankers. The chemical tankers are carrying hazardous chemical cargoes in their cargo tanks. When carrying hazardous chemicals in cargo tanks, the coating is required which is to provide safety barrier between the hull plate and the cargo. Therefore, capabilities of cargo tanks are of paramount importance for safe and efficient transport. Tank coatings to be applied to chemical tankers are epoxy coatings, zinc silicate coating, stainless steel coating, and marine line coating. This paper aims at conducting a numerical performance analysis of tank coatings in chemical tankers to contribute decision-making process of shipowner and safety professionals. To achieve this purpose, a multi-criterion decision-making (MCDM) tool is adopted: An Analytical Hierarchy Process (AHP) and Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) under interval type-2 fuzzy set (IT2Fs) environment. The outcomes of the numerical performance analysis showed that stainless steel type tank coating has the best performance since result of closeness coefficient value c( xj) is found 0.55. The findings of the research will contribute chemical tanker ship owners, safety inspectors, naval architects, and safety professionals during decision-making process of ideal cargo tank coating.","PeriodicalId":20667,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment","volume":"59 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2023-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81361805","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-31DOI: 10.1177/14750902231189917
N. Vladimir, I. Senjanović, Ivana Jovanović, S. Tomašević, Paul Jurišić
Large engineering structures like ships and other floating structures require reliable and complex computations to ensure their structural integrity over their lifetime. This work presents an analysis of the structural integrity of an aged single-bottom tanker during its towing from Croatia to a scrapheap in Turkey. The ship is subjected to wave loading (corresponding to the global response) and towing force (corresponding to the local response). Computations were performed by a general hydro-structure tool that combines a 3D finite element (FE) structural model and a 3D boundary element (BE) model based on the Rankine panel theory, according to the guidelines of the relevant classification society. Time domain simulations were performed to take account of Froude-Krylov nonlinearities for a wave determined within the Equivalent Design Wave (EDW) approach. After the calculation of wave loading and its transfer to the FE model of a ship structure, the stresses were calculated and compared with the allowable values. The local strength assessment of the ship forecastle deck structure was also performed, considering the prescribed towing force as an imposed load. Both the procedure and the used computational tools are general and can be applied to any kind of ship or other floating structure.
{"title":"Direct strength calculation of an aged single-bottom tanker during its towing in waves","authors":"N. Vladimir, I. Senjanović, Ivana Jovanović, S. Tomašević, Paul Jurišić","doi":"10.1177/14750902231189917","DOIUrl":"https://doi.org/10.1177/14750902231189917","url":null,"abstract":"Large engineering structures like ships and other floating structures require reliable and complex computations to ensure their structural integrity over their lifetime. This work presents an analysis of the structural integrity of an aged single-bottom tanker during its towing from Croatia to a scrapheap in Turkey. The ship is subjected to wave loading (corresponding to the global response) and towing force (corresponding to the local response). Computations were performed by a general hydro-structure tool that combines a 3D finite element (FE) structural model and a 3D boundary element (BE) model based on the Rankine panel theory, according to the guidelines of the relevant classification society. Time domain simulations were performed to take account of Froude-Krylov nonlinearities for a wave determined within the Equivalent Design Wave (EDW) approach. After the calculation of wave loading and its transfer to the FE model of a ship structure, the stresses were calculated and compared with the allowable values. The local strength assessment of the ship forecastle deck structure was also performed, considering the prescribed towing force as an imposed load. Both the procedure and the used computational tools are general and can be applied to any kind of ship or other floating structure.","PeriodicalId":20667,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment","volume":"135 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2023-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89576653","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-23DOI: 10.1177/14750902231188393
Bian Tao, Liu Liangliang, Cai Wenhao, Jiang Wen, Liu Zhiwen
This paper proposes a multi-objective optimization design method for shaftless rim-driven thruster (RDT) based on the ISIGHT platform. The pitch ratio, the blade area ratio and the advance coefficient of RDT were considered as the design optimization variables, the thrust and efficiency of the RDT were the optimization objectives. The multi-objective optimization design method was based on the surrogate module and the optimization module in the ISIGHT platform. Two analytical methods (response surface methodology (RSM) and radial basis function Model (RBF)) were used to build the surrogate model. The Muti-Island GA optimization algorithm was adopted in the optimization module. The paper indicates that both RSM model and RBF model are feasible to build the surrogate model, the RBF model has better accuracy and reliability than RSM model. The blade obtained by RBF method has larger thrust and smaller torque than that of the blade obtained by RSM method. For the large advance coefficient ( J > 0.6), the efficiency of the blade obtained by RBF method is slightly higher than that of the blade obtained by RSM method.
{"title":"Multi-objective optimization design of shaftless rim-driven thruster","authors":"Bian Tao, Liu Liangliang, Cai Wenhao, Jiang Wen, Liu Zhiwen","doi":"10.1177/14750902231188393","DOIUrl":"https://doi.org/10.1177/14750902231188393","url":null,"abstract":"This paper proposes a multi-objective optimization design method for shaftless rim-driven thruster (RDT) based on the ISIGHT platform. The pitch ratio, the blade area ratio and the advance coefficient of RDT were considered as the design optimization variables, the thrust and efficiency of the RDT were the optimization objectives. The multi-objective optimization design method was based on the surrogate module and the optimization module in the ISIGHT platform. Two analytical methods (response surface methodology (RSM) and radial basis function Model (RBF)) were used to build the surrogate model. The Muti-Island GA optimization algorithm was adopted in the optimization module. The paper indicates that both RSM model and RBF model are feasible to build the surrogate model, the RBF model has better accuracy and reliability than RSM model. The blade obtained by RBF method has larger thrust and smaller torque than that of the blade obtained by RSM method. For the large advance coefficient ( J > 0.6), the efficiency of the blade obtained by RBF method is slightly higher than that of the blade obtained by RSM method.","PeriodicalId":20667,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment","volume":"4 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2023-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89249956","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-21DOI: 10.1177/14750902231185807
P. Kundu, A. De
Generating more usable power annually from the river and tidal currents is essential to improving cost-effectiveness. Among various alternative options, the performance improvement of the blade foil has been considered in this work. When the fluid over the blade surface loses kinetic energy, flow separation occurs. The lift forces are reduced by flow separation, which finally results in less power production by the horizontal axis current turbine. To extract more power, it is necessary to overcome this flow separation. This paper presents a passive flow control method using tubes at regular intervals on the blade section to improve its performance considering its application on a horizontal axis current turbine. The tube inlet and outlet positions are determined by analyzing the force coefficients, glide ratio, and stall angle for a specific angle of attack. Finally, the performance characteristics are compared between the baseline and the modified hydrofoil. The maximum lift coefficient of the hydrofoil is increased by 15.7%. Also, the maximum glide ratios are considerably increased beyond the stall of the baseline profile. From the numerical results, it can be concluded that tubes inserted at regular intervals on the hydrofoil significantly increase its performance at a higher angle of attack.
{"title":"Performance analysis of a horizontal axis current turbine blade section with inserted tube","authors":"P. Kundu, A. De","doi":"10.1177/14750902231185807","DOIUrl":"https://doi.org/10.1177/14750902231185807","url":null,"abstract":"Generating more usable power annually from the river and tidal currents is essential to improving cost-effectiveness. Among various alternative options, the performance improvement of the blade foil has been considered in this work. When the fluid over the blade surface loses kinetic energy, flow separation occurs. The lift forces are reduced by flow separation, which finally results in less power production by the horizontal axis current turbine. To extract more power, it is necessary to overcome this flow separation. This paper presents a passive flow control method using tubes at regular intervals on the blade section to improve its performance considering its application on a horizontal axis current turbine. The tube inlet and outlet positions are determined by analyzing the force coefficients, glide ratio, and stall angle for a specific angle of attack. Finally, the performance characteristics are compared between the baseline and the modified hydrofoil. The maximum lift coefficient of the hydrofoil is increased by 15.7%. Also, the maximum glide ratios are considerably increased beyond the stall of the baseline profile. From the numerical results, it can be concluded that tubes inserted at regular intervals on the hydrofoil significantly increase its performance at a higher angle of attack.","PeriodicalId":20667,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment","volume":"3 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2023-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89877311","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-10DOI: 10.1177/14750902231184096
JaeHyeck Lee, Yoon-Seo Nam, Yuming Liu, Hee-Joo Yang
In this study, the predictability of ocean wave fields is considered based on marine radar measurement data. Phase-resolved components obtained by applying 3D FFT-based reconstruction to a sequence of radar images are utilized for wave field prediction, and two different prediction approaches are introduced: (i) snapshot data-based prediction through the adjustment of the frequency and phase of each component, and (ii) spatiotemporal data-based prediction through the data assimilation for reconstructed wave fields. Furthermore, the time evolution of a predictable zone is derived for different shapes of measurement domains including rectangular and ring-shaped domains. To validate the proposed wave propagation modeling method, numerical simulations are conducted on synthetic radar images created by reflecting geometrical shadowing effects, and the prediction accuracy is examined in relation to the derived predictable zone. Lastly, the forecasting performance, which is represented by the predictable time range at a radar location, is discussed with respect to the prediction techniques, specifications of the reconstruction domain, and moving measurements.
{"title":"Study on predictability of ocean wave fields based on marine radar measurement data","authors":"JaeHyeck Lee, Yoon-Seo Nam, Yuming Liu, Hee-Joo Yang","doi":"10.1177/14750902231184096","DOIUrl":"https://doi.org/10.1177/14750902231184096","url":null,"abstract":"In this study, the predictability of ocean wave fields is considered based on marine radar measurement data. Phase-resolved components obtained by applying 3D FFT-based reconstruction to a sequence of radar images are utilized for wave field prediction, and two different prediction approaches are introduced: (i) snapshot data-based prediction through the adjustment of the frequency and phase of each component, and (ii) spatiotemporal data-based prediction through the data assimilation for reconstructed wave fields. Furthermore, the time evolution of a predictable zone is derived for different shapes of measurement domains including rectangular and ring-shaped domains. To validate the proposed wave propagation modeling method, numerical simulations are conducted on synthetic radar images created by reflecting geometrical shadowing effects, and the prediction accuracy is examined in relation to the derived predictable zone. Lastly, the forecasting performance, which is represented by the predictable time range at a radar location, is discussed with respect to the prediction techniques, specifications of the reconstruction domain, and moving measurements.","PeriodicalId":20667,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment","volume":"78 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2023-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90884820","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-24DOI: 10.1177/14750902231183198
Ankit Nehra, V. Rajagopalan
The twin island concept is the most recent innovation in the top-deck architecture of an aircraft carrier. The carrier’s bluff body design presents the pilot with a number of difficulties, with landing on deck posing the biggest problem. The goal of the current study is to carry out the numerical analysis of the aerodynamic behaviour of twin island structure on Generic Aircraft Carrier. The flow characterization has been performed utilizing the normalized axial velocity and turbulent kinetic energy as aids for establishing pilot workload along the glideslope line. In this paper, multiple transverse planes cut across perpendicular to the flow direction are used to analyse the flow across the flight deck of twin island GAC and its downstream. The impacts of the two islands’ longitudinal translations with regard to the initial GAC position were then investigated and the results were analysed and compiled with reference to the landing approach path of the aircraft. The results show that the twin island designs are preferable to a single island. The maximum advantage in terms of turbulence reduction is achieved when the bifurcated islands are longitudinally repositioned forward of the original single island design position. The modified design not only achieves a 72% reduction in peak turbulence but also provides an additional time advantage to the pilot for assessing the environmental conditions while he is approaching the carrier flight deck for landing thus aiding to efficiently and effectively manage the workload. The findings of this study can act as a driving force for the integration and application of twin island concept in future design plans for floating structures and further studies in the field.
{"title":"Numeric assessment of the effect of the twin island design on the airflow dynamics around a generic aircraft carrier","authors":"Ankit Nehra, V. Rajagopalan","doi":"10.1177/14750902231183198","DOIUrl":"https://doi.org/10.1177/14750902231183198","url":null,"abstract":"The twin island concept is the most recent innovation in the top-deck architecture of an aircraft carrier. The carrier’s bluff body design presents the pilot with a number of difficulties, with landing on deck posing the biggest problem. The goal of the current study is to carry out the numerical analysis of the aerodynamic behaviour of twin island structure on Generic Aircraft Carrier. The flow characterization has been performed utilizing the normalized axial velocity and turbulent kinetic energy as aids for establishing pilot workload along the glideslope line. In this paper, multiple transverse planes cut across perpendicular to the flow direction are used to analyse the flow across the flight deck of twin island GAC and its downstream. The impacts of the two islands’ longitudinal translations with regard to the initial GAC position were then investigated and the results were analysed and compiled with reference to the landing approach path of the aircraft. The results show that the twin island designs are preferable to a single island. The maximum advantage in terms of turbulence reduction is achieved when the bifurcated islands are longitudinally repositioned forward of the original single island design position. The modified design not only achieves a 72% reduction in peak turbulence but also provides an additional time advantage to the pilot for assessing the environmental conditions while he is approaching the carrier flight deck for landing thus aiding to efficiently and effectively manage the workload. The findings of this study can act as a driving force for the integration and application of twin island concept in future design plans for floating structures and further studies in the field.","PeriodicalId":20667,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment","volume":"2 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2023-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89273535","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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