A new approach that models lift and drag hydrodynamic force signals operating over cylindrical structures was developed and validated. This approach is based on stochastic auto regressive moving average with exogenous...A new approach that models lift and drag hydrodynamic force signals operating over cylindrical structures was developed and validated. This approach is based on stochastic auto regressive moving average with exogenous （ARMAX） input and its time-varying form, TARMAX. Model structure selection and parameter estimation were discussed while considering the validation stage. In this papel; the cylindrical structure was considered as a dynamic system with an incoming water wave and resulting forces as the input and outputs, respectively. The experimental data, used in this study, were collected from a full-scale rough vertical cylinder at the Delft Hydraulics Laboratory. The practicality of the proposed method and also its efficiency in structural modeling were demonstrated through applying two hydrodynamic force components. For this purpose, an ARMAX model is first used to capture the dynamics of the process, relating in-line forces provided by water waves; secondly, the TARMAX model was applied to modeling and analysis of the lift forces on the cylinder. The evaluation of the lift force by the TARMAX model shows the model is successful in modeling the force from the surface elevation.展开更多
This study examines the hydrodynamic performance of short-crested wave interaction with a new porous cylindrical structure by using the scaled boundary finite element method （SBFEM）, which is a semi-analytical techn...This study examines the hydrodynamic performance of short-crested wave interaction with a new porous cylindrical structure by using the scaled boundary finite element method （SBFEM）, which is a semi-analytical technique combining the advantages of the finite element method and the boundary element method and with its own special features as well. The cylindrical structure consists of dual arc-shaped porous outer cylinders circumscribing an impermeable inner cylinder. A central feature of the newly extended method is that two virtual outer cylinders extending the arc-shaped porous outer cylinders with the same centre are introduced and variable porous-effect parameters are also introduced for the two virtual cylinders, so that the final SBFEM quation still can be handled in a closed-form analytical manner in the radial direction and by a finite element approximation in the circumferential direction. The entire computational domain is divided into two bounded and one unbounded domains, and a variational principle formulation is used to derive the SBFEM equation in each sub-domain. The velocity potential in bounded and unbounded domains is formulated using sets of Bessel and Hankel functions respectively, and the unknown coefficients are determined from the matching conditions. The results of numerical verification show that the approach discretises only the outermost virtual cylinder with surface finite-elements and fewer elements are required to obtain very accurate results.Influences of the incident wave parameters and structural configurations on the hydrodynamics are examined.展开更多
文摘A new approach that models lift and drag hydrodynamic force signals operating over cylindrical structures was developed and validated. This approach is based on stochastic auto regressive moving average with exogenous （ARMAX） input and its time-varying form, TARMAX. Model structure selection and parameter estimation were discussed while considering the validation stage. In this papel; the cylindrical structure was considered as a dynamic system with an incoming water wave and resulting forces as the input and outputs, respectively. The experimental data, used in this study, were collected from a full-scale rough vertical cylinder at the Delft Hydraulics Laboratory. The practicality of the proposed method and also its efficiency in structural modeling were demonstrated through applying two hydrodynamic force components. For this purpose, an ARMAX model is first used to capture the dynamics of the process, relating in-line forces provided by water waves; secondly, the TARMAX model was applied to modeling and analysis of the lift forces on the cylinder. The evaluation of the lift force by the TARMAX model shows the model is successful in modeling the force from the surface elevation.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51121005 and 51138001)the China-Germany Joint Research Project (Grant No. GZ566)
文摘This study examines the hydrodynamic performance of short-crested wave interaction with a new porous cylindrical structure by using the scaled boundary finite element method （SBFEM）, which is a semi-analytical technique combining the advantages of the finite element method and the boundary element method and with its own special features as well. The cylindrical structure consists of dual arc-shaped porous outer cylinders circumscribing an impermeable inner cylinder. A central feature of the newly extended method is that two virtual outer cylinders extending the arc-shaped porous outer cylinders with the same centre are introduced and variable porous-effect parameters are also introduced for the two virtual cylinders, so that the final SBFEM quation still can be handled in a closed-form analytical manner in the radial direction and by a finite element approximation in the circumferential direction. The entire computational domain is divided into two bounded and one unbounded domains, and a variational principle formulation is used to derive the SBFEM equation in each sub-domain. The velocity potential in bounded and unbounded domains is formulated using sets of Bessel and Hankel functions respectively, and the unknown coefficients are determined from the matching conditions. The results of numerical verification show that the approach discretises only the outermost virtual cylinder with surface finite-elements and fewer elements are required to obtain very accurate results.Influences of the incident wave parameters and structural configurations on the hydrodynamics are examined.
