由于水底和水面的影响,结构在有限水深环境中的辐射声场与在自由空间中的辐射声场有很大区别。为了更高效准确地分析有限水深环境中大规模结构的辐射声场,文章构建一种快速边界元法(boundary element method,BEM)。采用宽频快速多极算...由于水底和水面的影响,结构在有限水深环境中的辐射声场与在自由空间中的辐射声场有很大区别。为了更高效准确地分析有限水深环境中大规模结构的辐射声场,文章构建一种快速边界元法(boundary element method,BEM)。采用宽频快速多极算法对计算过程进行加速处理,针对算法中最为耗时的M2L/F2H变换过程,通过建立判定准则将均匀层格林函数中的多阶虚源分为近场和远场,从而设计不同求解方案,极大减少M2L/F2H的变换次数,显著提高求解效率。数值算例验证了文章方法的准确性和高效性,并体现出该方法在浅海声学分析中的工程潜力。展开更多
To design a propeller for ship power plant,the interaction between ship hull and propeller must be taken into account.The main concern is to apply the wake effect of ship stern on the propeller performance.In this pap...To design a propeller for ship power plant,the interaction between ship hull and propeller must be taken into account.The main concern is to apply the wake effect of ship stern on the propeller performance.In this paper,a coupled BEM(Boundary Element Method)/RANS(Renolds-Averaged Navier−Stokes)solver is used to simulate propeller behind the hull in the self-propulsion test.The motivation of this work is to develop a practical tool to design marine propulsion system without suffering long computational time.An unsteady boundary element method which is also known as panel method is chosen to estimate the propeller forces.Propeller wakes are treated using a time marching wake alignment method.Also,a RANS code coupled with VoF equation is developed to consider the ship motions and wake field effects in the problem.A coupling algorithm is developed to interchange ship wake field to the potential flow solver and propeller thrust to the RANS code.Based on the difference between hull resistance and the propeller thrust,a PI controller is developed to compute the propeller RPM in every time step.Verification of the solver is carried out using the towing tank test report of a 50 m oceanography research vessel.Wake factor and trust deduction coefficient are estimated numerically.Also,the wake rollup pattern of the propeller in open water is compared with the propeller in real wake field.展开更多
A three-dimensional mathematical hydrodynamic model associated with surface wave radiation by a floating rectangular box-type structure due to heave,sway,and roll motions in finite water depth is investigated based on...A three-dimensional mathematical hydrodynamic model associated with surface wave radiation by a floating rectangular box-type structure due to heave,sway,and roll motions in finite water depth is investigated based on small amplitude water wave theory and linear structural response.The analytical expressions for the radiation potentials,wave forces,and hydrodynamic coefficients are presented based on matched eigenfunction expansion method(MEFEM).The correctness of the analytical results of wave forces is compared with the construction of a numerical model using the open-source boundary element method code NEMOH.In addition,the present result is compared with the existing published experimental results available in the literature.The effects of the different design parameters on the floating box-type rectangular structure are studied by analyzing the vertical wave force,horizontal wave force,torque,added mass,and damping coefficients due to the heave,sway,and roll motions,and the comparison analysis between the forces is also analyzed in detail.Further,the effect of reflection and transmission coefficients by varying the structural width and drafts are analyzed.展开更多
In this study,we focus on the numerical modelling of the interaction between waves and submerged structures in the presence of a uniform flow current.Both the same and opposite senses of wave propagation are considere...In this study,we focus on the numerical modelling of the interaction between waves and submerged structures in the presence of a uniform flow current.Both the same and opposite senses of wave propagation are considered.The main objective is an understanding of the effect of the current and various geometrical parameters on the reflection coefficient.The wave used in the study is based on potential theory,and the submerged structures consist of two rectangular breakwaters positioned at a fixed distance from each other and attached to the bottom of a wave flume.The numerical modeling approach employed in this work relies on the Boundary Element Method(BEM).The results are compared with experimental data to validate the approach.The findings of the study demonstrate that the double rectangular breakwater configuration exhibits superior wave attenuation abilities if compared to a single rectangular breakwater,particularly at low wavenumbers.Furthermore,the study reveals that wave mitigation is more pronounced when the current and wave propagation are coplanar,whereas it is less effective in the case of opposing current.展开更多
文摘由于水底和水面的影响,结构在有限水深环境中的辐射声场与在自由空间中的辐射声场有很大区别。为了更高效准确地分析有限水深环境中大规模结构的辐射声场,文章构建一种快速边界元法(boundary element method,BEM)。采用宽频快速多极算法对计算过程进行加速处理,针对算法中最为耗时的M2L/F2H变换过程,通过建立判定准则将均匀层格林函数中的多阶虚源分为近场和远场,从而设计不同求解方案,极大减少M2L/F2H的变换次数,显著提高求解效率。数值算例验证了文章方法的准确性和高效性,并体现出该方法在浅海声学分析中的工程潜力。
文摘To design a propeller for ship power plant,the interaction between ship hull and propeller must be taken into account.The main concern is to apply the wake effect of ship stern on the propeller performance.In this paper,a coupled BEM(Boundary Element Method)/RANS(Renolds-Averaged Navier−Stokes)solver is used to simulate propeller behind the hull in the self-propulsion test.The motivation of this work is to develop a practical tool to design marine propulsion system without suffering long computational time.An unsteady boundary element method which is also known as panel method is chosen to estimate the propeller forces.Propeller wakes are treated using a time marching wake alignment method.Also,a RANS code coupled with VoF equation is developed to consider the ship motions and wake field effects in the problem.A coupling algorithm is developed to interchange ship wake field to the potential flow solver and propeller thrust to the RANS code.Based on the difference between hull resistance and the propeller thrust,a PI controller is developed to compute the propeller RPM in every time step.Verification of the solver is carried out using the towing tank test report of a 50 m oceanography research vessel.Wake factor and trust deduction coefficient are estimated numerically.Also,the wake rollup pattern of the propeller in open water is compared with the propeller in real wake field.
基金the project Hydroelastic behaviour of horizontal flexible floating structures for applications to Floating Breakwaters and Wave Energy Converters(HYDROELASTWEB),which is co-funded by the European Regional Development Fund(Fundo Europeu de Desenvolvimento Regional-FEDER)by the Portuguese Foundation for Science and Technology(Funda??o para a Ciência e a Tecnologia-FCT)under contract 031488_770(PTDC/ECI-EGC/31488/2017)+1 种基金a Researcher by FCT,through Scientific Employment Stimulus,Individual support under Contract No.CEECIND/04879/2017the Strategic Research Plan of the Centre for Marine Technology and Ocean Engineering(CENTEC),which is financed by the Portuguese Foundation for Science and Technology(Funda??o para a Ciência e Tecnologia-FCT)under contract UIDB/UIDP/00134/2020。
文摘A three-dimensional mathematical hydrodynamic model associated with surface wave radiation by a floating rectangular box-type structure due to heave,sway,and roll motions in finite water depth is investigated based on small amplitude water wave theory and linear structural response.The analytical expressions for the radiation potentials,wave forces,and hydrodynamic coefficients are presented based on matched eigenfunction expansion method(MEFEM).The correctness of the analytical results of wave forces is compared with the construction of a numerical model using the open-source boundary element method code NEMOH.In addition,the present result is compared with the existing published experimental results available in the literature.The effects of the different design parameters on the floating box-type rectangular structure are studied by analyzing the vertical wave force,horizontal wave force,torque,added mass,and damping coefficients due to the heave,sway,and roll motions,and the comparison analysis between the forces is also analyzed in detail.Further,the effect of reflection and transmission coefficients by varying the structural width and drafts are analyzed.
文摘In this study,we focus on the numerical modelling of the interaction between waves and submerged structures in the presence of a uniform flow current.Both the same and opposite senses of wave propagation are considered.The main objective is an understanding of the effect of the current and various geometrical parameters on the reflection coefficient.The wave used in the study is based on potential theory,and the submerged structures consist of two rectangular breakwaters positioned at a fixed distance from each other and attached to the bottom of a wave flume.The numerical modeling approach employed in this work relies on the Boundary Element Method(BEM).The results are compared with experimental data to validate the approach.The findings of the study demonstrate that the double rectangular breakwater configuration exhibits superior wave attenuation abilities if compared to a single rectangular breakwater,particularly at low wavenumbers.Furthermore,the study reveals that wave mitigation is more pronounced when the current and wave propagation are coplanar,whereas it is less effective in the case of opposing current.
