taking average last These are assumed dependent on velocity and amplitude Force coefficients
这些假设取决于速度和振幅力系数
{"title":"CFD-based identification of hydrodynamic coefficients for a rudder","authors":"H. Svensson","doi":"10.2218/marine2021.6787","DOIUrl":"https://doi.org/10.2218/marine2021.6787","url":null,"abstract":"taking average last These are assumed dependent on velocity and amplitude Force coefficients","PeriodicalId":367395,"journal":{"name":"The 9th Conference on Computational Methods in Marine Engineering (Marine 2021)","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121283207","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Noise generated by renewable energy devices may impact local wildlife and interfere with military navigation techniques. Given the particular challenges posed by underwater sound propagation, careful analysis of this phenomenon is required. To conduct such an analysis, a model that is able to integrate detailed environmental descriptions and low frequency computations is sought. For these purposes, it has been found that normal mode models are the most suited to the task at hand, in particular the classical KRAKEN algorithm. In this article, the advantages of normal mode models over ray-tracing ones such as BELLHOP will be presented. Furthermore, the algorithm’s performance is numerically verified through the employment of mesh refinement studies to evaluate its numerical uncertainty convergence characteristics. Finally, the normal mode method’s capabilities are validated against experimental data measured near an energy-generating device installed off the coast of Peniche, Portugal. At frequencies above 1000 Hz, it was found that the normal mode solution closely followed the trends observable in the experimental data. Between 500 and 1000 Hz, difficulties in assembling a field solution over the domain arose. Below these frequencies, a clear break-down of the normal mode assumptions was observed. The normal mode method has been concluded to be a strong candidate to predict sound propagation from marine structures, but more work is needed to improve the calculation of near-field effects, potentially by use of Green’s function algorithms.
{"title":"Underwater Acoustic Impact of a Marine Renewable Energy Device","authors":"Pedro Pregitzer, F. Lau, G. Vaz, E. Cruz","doi":"10.2218/marine2021.6843","DOIUrl":"https://doi.org/10.2218/marine2021.6843","url":null,"abstract":"Noise generated by renewable energy devices may impact local wildlife and interfere with military navigation techniques. Given the particular challenges posed by underwater sound propagation, careful analysis of this phenomenon is required. To conduct such an analysis, a model that is able to integrate detailed environmental descriptions and low frequency computations is sought. For these purposes, it has been found that normal mode models are the most suited to the task at hand, in particular the classical KRAKEN algorithm. In this article, the advantages of normal mode models over ray-tracing ones such as BELLHOP will be presented. Furthermore, the algorithm’s performance is numerically verified through the employment of mesh refinement studies to evaluate its numerical uncertainty convergence characteristics. Finally, the normal mode method’s capabilities are validated against experimental data measured near an energy-generating device installed off the coast of Peniche, Portugal. At frequencies above 1000 Hz, it was found that the normal mode solution closely followed the trends observable in the experimental data. Between 500 and 1000 Hz, difficulties in assembling a field solution over the domain arose. Below these frequencies, a clear break-down of the normal mode assumptions was observed. The normal mode method has been concluded to be a strong candidate to predict sound propagation from marine structures, but more work is needed to improve the calculation of near-field effects, potentially by use of Green’s function algorithms.","PeriodicalId":367395,"journal":{"name":"The 9th Conference on Computational Methods in Marine Engineering (Marine 2021)","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125601020","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In comparison to conventional ship propulsion systems, the cycloidal propeller replaces the ship's propeller with individual, circularly arranged blades that rotate about the vertical axis. A lever mechanism is used to change the pitch of the blades cyclically over the rotation of the drive, thereby adjusting the direction and velocity of the propulsion. A functioning geometry of the lever mechanism for fulfilling the required boundary conditions was developed at the Chair of Machine Elements and based on the available design parameters, the entire propulsion system was transferred into a multibody system simulation model. The representation of different driving maneuvers is possible by modeling the position- and angle-dependent water loads on the blades. The symmetric design of a second drive allows fundamental investigations to determine the effects of using more than one drive on the direction and velocity of travel and to evaluate the effects of the design-related violation of the normal law.
{"title":"Kinematics and Load Conditions at a Cycloidal Propeller","authors":"T. Rosenloecher, BS Schlecht","doi":"10.2218/marine2021.6830","DOIUrl":"https://doi.org/10.2218/marine2021.6830","url":null,"abstract":"In comparison to conventional ship propulsion systems, the cycloidal propeller replaces the ship's propeller with individual, circularly arranged blades that rotate about the vertical axis. A lever mechanism is used to change the pitch of the blades cyclically over the rotation of the drive, thereby adjusting the direction and velocity of the propulsion. A functioning geometry of the lever mechanism for fulfilling the required boundary conditions was developed at the Chair of Machine Elements and based on the available design parameters, the entire propulsion system was transferred into a multibody system simulation model. The representation of different driving maneuvers is possible by modeling the position- and angle-dependent water loads on the blades. The symmetric design of a second drive allows fundamental investigations to determine the effects of using more than one drive on the direction and velocity of travel and to evaluate the effects of the design-related violation of the normal law.","PeriodicalId":367395,"journal":{"name":"The 9th Conference on Computational Methods in Marine Engineering (Marine 2021)","volume":"102 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132637218","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
. Much work has been done over the past years to obtain a better understanding of cavitation, as well as to predict and alleviate its effects on performance. Particularly, lifting-surface sheet cavitation is addressed in various works as a free-streamline problem. Typically, a potential solver is used in conjunction with a geometric criterion to determine the shape of the cavity, whereas an iterative scheme is employed to locate the cavity surface. In this work we reformulate the problem of steady partially cavitating two-dimensional hydrofoils in a shape-optimization setup. The sensitivities required for the gradient-based optimization algorithm are derived using the continuous adjoint method. The objective function is formulated based on the assumption that the pressure on the cavity is constant and is evaluated using a source-vorticity BEM solver, whereas the control points of the B-spline cavity parametrization serve as design variables. The proposed numerical scheme is validated and found to predict well both the cavity shape and the cavitation number. Moreover, the benefits of using the adjoint method to predict the sensitivity derivatives are highlighted in a selected study case.
{"title":"Prediction Model for Partially Cavitating Hydrofoils based on Sensitivity Derivatives","authors":"D. Anevlavi, K. Belibassakis","doi":"10.2218/marine2021.6800","DOIUrl":"https://doi.org/10.2218/marine2021.6800","url":null,"abstract":". Much work has been done over the past years to obtain a better understanding of cavitation, as well as to predict and alleviate its effects on performance. Particularly, lifting-surface sheet cavitation is addressed in various works as a free-streamline problem. Typically, a potential solver is used in conjunction with a geometric criterion to determine the shape of the cavity, whereas an iterative scheme is employed to locate the cavity surface. In this work we reformulate the problem of steady partially cavitating two-dimensional hydrofoils in a shape-optimization setup. The sensitivities required for the gradient-based optimization algorithm are derived using the continuous adjoint method. The objective function is formulated based on the assumption that the pressure on the cavity is constant and is evaluated using a source-vorticity BEM solver, whereas the control points of the B-spline cavity parametrization serve as design variables. The proposed numerical scheme is validated and found to predict well both the cavity shape and the cavitation number. Moreover, the benefits of using the adjoint method to predict the sensitivity derivatives are highlighted in a selected study case.","PeriodicalId":367395,"journal":{"name":"The 9th Conference on Computational Methods in Marine Engineering (Marine 2021)","volume":"382 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122346544","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Kalikatzarakis, Andrea Coraddu, M. Atlar, G. Tani, S. Gaggero, D. Villa, L. Oneto
The potential impact of ships underwater radiated noise (URN) on marine fauna has become an important issue. The most dominant noise source on a propeller-driven vessel is propeller cavitation, and the accurate prediction of its noise signature is fundamental for the design process. In this work, we investigate the potential of using low-computational-cost methods for the prediction of URN from cavitating marine propellers that can be conveniently implemented within the design process. We compare computational and experimental results on a subset of the Meridian standard propeller series, behind different severities of axial wake, for a total of 432 experiments.
{"title":"Computational Prediction of Propeller Cavitation Noise","authors":"M. Kalikatzarakis, Andrea Coraddu, M. Atlar, G. Tani, S. Gaggero, D. Villa, L. Oneto","doi":"10.2218/marine2021.6784","DOIUrl":"https://doi.org/10.2218/marine2021.6784","url":null,"abstract":"The potential impact of ships underwater radiated noise (URN) on marine fauna has become an important issue. The most dominant noise source on a propeller-driven vessel is propeller cavitation, and the accurate prediction of its noise signature is fundamental for the design process. In this work, we investigate the potential of using low-computational-cost methods for the prediction of URN from cavitating marine propellers that can be conveniently implemented within the design process. We compare computational and experimental results on a subset of the Meridian standard propeller series, behind different severities of axial wake, for a total of 432 experiments.","PeriodicalId":367395,"journal":{"name":"The 9th Conference on Computational Methods in Marine Engineering (Marine 2021)","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130767432","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yosuke Kobayashi, Y. Okada, Kenta Katayama, Takamichi Hiroi, D. Wako, Yasuo Ichinose
Propeller hub cap with fins (HCWF) is an energy-saving device, which is easily installed and replaced on ships in comparison with the other energy saving devices. Nakashima Propeller has developed a HCWF named ECO-Cap. This study discusses relations between energy-saving effects, propeller geometries, and flow fields behind the propellers based on propeller open water tests and underwater stereoscopic particle image velocimetry measurements in a towing tank using models of an ECO-Cap and multiple propellers. The test results showed that the ECO-Cap can suppress hub vortices and improve propulsion efficiency up to 4.7%. The propeller which has less number of blades or root-loaded pitch distribution strengthened hub vortices during a normal cap without fins. The intensity of the hub vortices was different during the normal cap between the propellers but almost the same level regardless of the propellers during the ECO-Cap. The results suggest that potential energy-saving amount by the ECO-Cap largely depends on the intensity of the hub vortices during the normal cap. Including the energy-saving effects of the ECO-Cap into the propeller open water efficiency, ranking of the propulsion efficiency changed from the original propeller open water efficiency without the ECO-Cap. The results showed importance of designing propellers and HCWFs considering interaction between components.
{"title":"Effects of Propeller Pitch and Number of Blades on Energy Saving of an ECO-Cap","authors":"Yosuke Kobayashi, Y. Okada, Kenta Katayama, Takamichi Hiroi, D. Wako, Yasuo Ichinose","doi":"10.2218/marine2021.6807","DOIUrl":"https://doi.org/10.2218/marine2021.6807","url":null,"abstract":"Propeller hub cap with fins (HCWF) is an energy-saving device, which is easily installed and replaced on ships in comparison with the other energy saving devices. Nakashima Propeller has developed a HCWF named ECO-Cap. This study discusses relations between energy-saving effects, propeller geometries, and flow fields behind the propellers based on propeller open water tests and underwater stereoscopic particle image velocimetry measurements in a towing tank using models of an ECO-Cap and multiple propellers. The test results showed that the ECO-Cap can suppress hub vortices and improve propulsion efficiency up to 4.7%. The propeller which has less number of blades or root-loaded pitch distribution strengthened hub vortices during a normal cap without fins. The intensity of the hub vortices was different during the normal cap between the propellers but almost the same level regardless of the propellers during the ECO-Cap. The results suggest that potential energy-saving amount by the ECO-Cap largely depends on the intensity of the hub vortices during the normal cap. Including the energy-saving effects of the ECO-Cap into the propeller open water efficiency, ranking of the propulsion efficiency changed from the original propeller open water efficiency without the ECO-Cap. The results showed importance of designing propellers and HCWFs considering interaction between components.","PeriodicalId":367395,"journal":{"name":"The 9th Conference on Computational Methods in Marine Engineering (Marine 2021)","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132417296","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
. This paper presents loads on flexible tarps. Tarpaulins have become popular in the Aquacultures industry to replace regular nets in parts of classic cages. Such systems respond in a highly hydro elastic manner. This need to be accounted for in a load response assessment. This paper outlines a formulation for the calculation of wave loads on flexible tarps, as well as a hybrid solution for calculating loads on tarps located in larger systems with stiffer parts included. Model tank testing has been carried out for a tube used in the aquaculture industry. Analysis and measurements are compared. Results shows good correspondence and are discussed for general applicability.
{"title":"Loads from waves and current for flexible tarps","authors":"A. Berstad","doi":"10.2218/marine2021.6842","DOIUrl":"https://doi.org/10.2218/marine2021.6842","url":null,"abstract":". This paper presents loads on flexible tarps. Tarpaulins have become popular in the Aquacultures industry to replace regular nets in parts of classic cages. Such systems respond in a highly hydro elastic manner. This need to be accounted for in a load response assessment. This paper outlines a formulation for the calculation of wave loads on flexible tarps, as well as a hybrid solution for calculating loads on tarps located in larger systems with stiffer parts included. Model tank testing has been carried out for a tube used in the aquaculture industry. Analysis and measurements are compared. Results shows good correspondence and are discussed for general applicability.","PeriodicalId":367395,"journal":{"name":"The 9th Conference on Computational Methods in Marine Engineering (Marine 2021)","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124919186","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
. Simulation results are presented for a well established ship hydrodynamics validation case with the Japan Bulk Carrier (JBC). The results include the ship position, forces on the hull, water surface deformation and the stern flow. Simulation results are compared with measurements for all these quantities. The open source software OpenFOAM was employed, with finite volume numerics, RANS turbulence modelling, the volume-of-fluid method for the free surface, and ship motion functionality. In order to enhance the reproducibility of the results, the data files of the simulation case are made freely available. In combination with open source software, this allows for other research groups to re-simulate, modify and improve the case. Practical aspects of making this type of simulation data available are also discussed in the paper.
{"title":"Fully reproducible RANS ship hydrodynamics for the JBC validation case","authors":"Linnea Sjökvist, M. Liefvendahl, M. Winroth","doi":"10.2218/marine2021.6825","DOIUrl":"https://doi.org/10.2218/marine2021.6825","url":null,"abstract":". Simulation results are presented for a well established ship hydrodynamics validation case with the Japan Bulk Carrier (JBC). The results include the ship position, forces on the hull, water surface deformation and the stern flow. Simulation results are compared with measurements for all these quantities. The open source software OpenFOAM was employed, with finite volume numerics, RANS turbulence modelling, the volume-of-fluid method for the free surface, and ship motion functionality. In order to enhance the reproducibility of the results, the data files of the simulation case are made freely available. In combination with open source software, this allows for other research groups to re-simulate, modify and improve the case. Practical aspects of making this type of simulation data available are also discussed in the paper.","PeriodicalId":367395,"journal":{"name":"The 9th Conference on Computational Methods in Marine Engineering (Marine 2021)","volume":"1202 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128632740","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
With the gradual shift towards renewable energy sources (RES), the ocean is now being recognised as an enormous natural source of clean energy which can supply power ranging from ocean thermal energy conversion (OTEC) to tidal and wave energy. Wind turbines have also been taken out at sea to benefit from the more favourable wind conditions offshore. In fact, offshore wind energy has now become the most technically advanced marine-based technology. The total global installed offshore wind capacity reached 29 Giga-Watts (GW) by the end of 2019, which has been reported to be the best year for the offshore wind industry to date [1].
{"title":"Design Optimisation of Pressure Vessel Bundles for Offshore Hydro-pneumatic Energy Storage","authors":"C. Cutajar, T. Sant, R. Farrugia, D. Buhagiar","doi":"10.2218/marine2021.6782","DOIUrl":"https://doi.org/10.2218/marine2021.6782","url":null,"abstract":"With the gradual shift towards renewable energy sources (RES), the ocean is now being recognised as an enormous natural source of clean energy which can supply power ranging from ocean thermal energy conversion (OTEC) to tidal and wave energy. Wind turbines have also been taken out at sea to benefit from the more favourable wind conditions offshore. In fact, offshore wind energy has now become the most technically advanced marine-based technology. The total global installed offshore wind capacity reached 29 Giga-Watts (GW) by the end of 2019, which has been reported to be the best year for the offshore wind industry to date [1].","PeriodicalId":367395,"journal":{"name":"The 9th Conference on Computational Methods in Marine Engineering (Marine 2021)","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125334333","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Filippo Avanzi, Francesco De Vanna, E. Benini, Fabio Ruaro, William Gobbo
A parametric study is conducted to optimise the drag performance of a novel concept of ram inlet waterjet. The latter being an outboard device housing the whole propulsion system. The study follows the guidelines from aero-engines literature which account for the pre-entry streamtube drag in the computation of external hydrodynamic resistance. Flow field data are obtained by solving Reynolds-Averaged Navier-Stokes equations, with k − ω SST turbulence model, on a 2D axisymmetric domain. Reynolds number, based on propulsor’s highlight diameter and free stream velocity, is varied between 1 . 6 · 10 6 and 2 . 7 · 10 6 . For each far-field condition, 9 different mass flow rate values are imposed on the internal boundaries corresponding to the pump sections and resulting in an overall range of the machine flow coefficient of 0.32. Comparing performance among three geometries shows that walls’ negative gradients drastically affect the drag coefficient in the whole operating envelope. In particular, reduced cross-sectional dimensions and longer shapes favour smoother external outlines. These prove to reduce the system’s resistance, despite the augmented axial length. Contextually, the analysis of the capture streamtube through the mass flow capture ratio shows that this parameter is less effective in enhancing performance, especially when the internal geometry is kept unchanged.
为优化一种新型冲压式水射流的阻力性能，进行了参数化研究。后者是一个舷外装置，容纳整个推进系统。该研究遵循了航空发动机文献中关于计算外水动力阻力时考虑入口前流管阻力的指导原则。采用k−ω海温湍流模型，在二维轴对称区域上求解reynolds - average Navier-Stokes方程获得流场数据。根据推进器的光圈直径和自由流速度，雷诺数在1。6·10 6和2。7·10对于每个远场工况，在泵段对应的内部边界上施加9个不同的质量流量值，使机器流量系数的总体范围为0.32。对比三种几何形状的性能表明，壁面的负梯度极大地影响了整个运行包线的阻力系数。特别是，减少的横截面尺寸和较长的形状有利于光滑的外部轮廓。这些证明了减少系统的阻力，尽管增加轴向长度。在此背景下，通过质量流量捕获比对捕获流管进行分析表明，该参数在提高性能方面效果较差，特别是在内部几何形状保持不变的情况下。
{"title":"ANALYSIS OF DRAG SOURCES IN A FULLY SUBMERGED WATERJET","authors":"Filippo Avanzi, Francesco De Vanna, E. Benini, Fabio Ruaro, William Gobbo","doi":"10.2218/marine2021.6824","DOIUrl":"https://doi.org/10.2218/marine2021.6824","url":null,"abstract":"A parametric study is conducted to optimise the drag performance of a novel concept of ram inlet waterjet. The latter being an outboard device housing the whole propulsion system. The study follows the guidelines from aero-engines literature which account for the pre-entry streamtube drag in the computation of external hydrodynamic resistance. Flow field data are obtained by solving Reynolds-Averaged Navier-Stokes equations, with k − ω SST turbulence model, on a 2D axisymmetric domain. Reynolds number, based on propulsor’s highlight diameter and free stream velocity, is varied between 1 . 6 · 10 6 and 2 . 7 · 10 6 . For each far-field condition, 9 different mass flow rate values are imposed on the internal boundaries corresponding to the pump sections and resulting in an overall range of the machine flow coefficient of 0.32. Comparing performance among three geometries shows that walls’ negative gradients drastically affect the drag coefficient in the whole operating envelope. In particular, reduced cross-sectional dimensions and longer shapes favour smoother external outlines. These prove to reduce the system’s resistance, despite the augmented axial length. Contextually, the analysis of the capture streamtube through the mass flow capture ratio shows that this parameter is less effective in enhancing performance, especially when the internal geometry is kept unchanged.","PeriodicalId":367395,"journal":{"name":"The 9th Conference on Computational Methods in Marine Engineering (Marine 2021)","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121612199","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：