A time domain prediction of wave-induced ship motions by a Rankine panel method is investigated. Linear boundary conditions on free surface and mean wetted body surface are adopted, while the numerical damping method ...A time domain prediction of wave-induced ship motions by a Rankine panel method is investigated. Linear boundary conditions on free surface and mean wetted body surface are adopted, while the numerical damping method is used for the radiation conditions. The motions of two ships in regular head waves are computed by the present method. The related numerical results are compared with the experiment data and those from linear strip theory. The comparison shows satisfactory agreements for pitch and heave transfer functions.展开更多
In this paper,a CFD/CSD model coupling N-S equations and structural equations of motion in the time domain is described for aeroelastic analysis of large wind turbines.The structural modes of blades are analyzed with ...In this paper,a CFD/CSD model coupling N-S equations and structural equations of motion in the time domain is described for aeroelastic analysis of large wind turbines.The structural modes of blades are analyzed with one-dimensional beam models.By combining point matched sliding grid for wind turbine rotation and deforming grid for structural vibrations,a hybrid dynamic grid strategy is designed for the multi-block structured grid system of a wind turbine.The dual time-stepping approach and finite volume scheme are applied to the three-dimensional unsteady preconditioned N-S equations,and DES approach is employed to simulate the unsteady massively separated flows.A modal approach is adopted to calculate the structural response,and a predictor-corrector scheme is used to solve the structural equations of motion.CFD and CSD solvers are tightly coupled via successive iterations within each physical time step.As a result,a time-domain CFD/CSD model for aeroelastic analysis of a large wind turbine is achieved.The presented method is applied to the NH1500 large wind turbine under the rated condition,and the calculated aeroelastic characteristics agree well with those of the prescribed vortex wake method.展开更多
Most of the reported observations are about the dynamic properties of individual domain-walls in magnetic nanowires,but the properties of multiple stripe-domains have rarely been investigated.Here,we demonstrate a sim...Most of the reported observations are about the dynamic properties of individual domain-walls in magnetic nanowires,but the properties of multiple stripe-domains have rarely been investigated.Here,we demonstrate a simple but efficient scenario for multiple domains injection in magnetic nanowires.The domain-chains(DCs),a cluster of multiple domains,can be dynamically generated with tunable static properties.It is found that the number of domains in a single DC can be dynamically adjusted by varying the frequency of microwave field(MF)and the period of spin-polarized current(SPC)intensity.The static properties of the DCs,i.e.,its length,spacing,and period between neighboring DCs,can be dynamically controlled by regulating the frequency of MF and the intensity of SPC.We have also discussed the possibility of using domain-chains as information carries,which provides a meaningful approach for flexible multi-bit information storage applications.展开更多
Time-domain analysis is used to predict wave loading and motion responses for a ship travelling at a constant speed in regular oblique waves. The combined diffraction and radiation perturbations, caused by the steady ...Time-domain analysis is used to predict wave loading and motion responses for a ship travelling at a constant speed in regular oblique waves. The combined diffraction and radiation perturbations, caused by the steady forward speed of the ship and her motions , are considered as a distribution of normal velocities on the wetted hull surface. The ship-hull boundary condition is exactly fulfilled by expressing the fluid normal velocities as a finite series in terms of the body geometry and the incident wave potential. As far as the authors are aware, no similar work is published todate.The new theory is applied to predict forces and motions at forward speed for a Wigley ship-hull in head waves and a catamaran-ferry in oblique waves. Predictions are compared with published theoretical and experimental results for the Wigley ship-hull, and the comparison is good. For the catamaran, a self-propelled model is built and tested in the large towing tank and seakeeping basin of the China Ship Scientific Research Centre, Wuxi, China, in order to measure the six-degrees-of-freedom forces, moments and motions at forward speed in waves of different directions. Measurements are compared with predictions, and the comparison is generally good for the longitudinal motions thus verifying the analysis. For the transverse motions, acceptable discrepancies exist due to the non-inclusion in the analysis of rudder forces and viscous damping, and due differences in structural inertia properties between the physical model and the corresponding data used in the analysis. The inclusion of viscous damping in the time domain involves complex analysis and this problem is left to a future research.展开更多
A new hybrid model, which is based on domain decomposition and proposed by the authors is used for calculating the flow around a circular cylinder at low and middle Keulegan-Carpenter numbers (Kc=2～18)respectively.Th...A new hybrid model, which is based on domain decomposition and proposed by the authors is used for calculating the flow around a circular cylinder at low and middle Keulegan-Carpenter numbers (Kc=2～18)respectively.The vortex motion patterns in asymmetric regime,single pair(or transverse)regime and double pair(or diagonal)regime are successfully simulated.The calculated drag and inertial force coefficients are in better agreement with experimental data than other recent computational results.展开更多
文摘A time domain prediction of wave-induced ship motions by a Rankine panel method is investigated. Linear boundary conditions on free surface and mean wetted body surface are adopted, while the numerical damping method is used for the radiation conditions. The motions of two ships in regular head waves are computed by the present method. The related numerical results are compared with the experiment data and those from linear strip theory. The comparison shows satisfactory agreements for pitch and heave transfer functions.
基金supported by the National Basic Research Program of China ("973" Project) (Grant No. 2007CB714600)the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘In this paper,a CFD/CSD model coupling N-S equations and structural equations of motion in the time domain is described for aeroelastic analysis of large wind turbines.The structural modes of blades are analyzed with one-dimensional beam models.By combining point matched sliding grid for wind turbine rotation and deforming grid for structural vibrations,a hybrid dynamic grid strategy is designed for the multi-block structured grid system of a wind turbine.The dual time-stepping approach and finite volume scheme are applied to the three-dimensional unsteady preconditioned N-S equations,and DES approach is employed to simulate the unsteady massively separated flows.A modal approach is adopted to calculate the structural response,and a predictor-corrector scheme is used to solve the structural equations of motion.CFD and CSD solvers are tightly coupled via successive iterations within each physical time step.As a result,a time-domain CFD/CSD model for aeroelastic analysis of a large wind turbine is achieved.The presented method is applied to the NH1500 large wind turbine under the rated condition,and the calculated aeroelastic characteristics agree well with those of the prescribed vortex wake method.
基金Project supported by the National Natural Science Foundation of China(Grant No.11704191)the Jiangsu Specially-Appointed Professor,the Natural Science Foundation of Jiangsu Province of China(Grant No.BK20171026)the Six-Talent Peaks Project in Jiangsu Province,China(Grant No.XYDXX-038)
文摘Most of the reported observations are about the dynamic properties of individual domain-walls in magnetic nanowires,but the properties of multiple stripe-domains have rarely been investigated.Here,we demonstrate a simple but efficient scenario for multiple domains injection in magnetic nanowires.The domain-chains(DCs),a cluster of multiple domains,can be dynamically generated with tunable static properties.It is found that the number of domains in a single DC can be dynamically adjusted by varying the frequency of microwave field(MF)and the period of spin-polarized current(SPC)intensity.The static properties of the DCs,i.e.,its length,spacing,and period between neighboring DCs,can be dynamically controlled by regulating the frequency of MF and the intensity of SPC.We have also discussed the possibility of using domain-chains as information carries,which provides a meaningful approach for flexible multi-bit information storage applications.
文摘Time-domain analysis is used to predict wave loading and motion responses for a ship travelling at a constant speed in regular oblique waves. The combined diffraction and radiation perturbations, caused by the steady forward speed of the ship and her motions , are considered as a distribution of normal velocities on the wetted hull surface. The ship-hull boundary condition is exactly fulfilled by expressing the fluid normal velocities as a finite series in terms of the body geometry and the incident wave potential. As far as the authors are aware, no similar work is published todate.The new theory is applied to predict forces and motions at forward speed for a Wigley ship-hull in head waves and a catamaran-ferry in oblique waves. Predictions are compared with published theoretical and experimental results for the Wigley ship-hull, and the comparison is good. For the catamaran, a self-propelled model is built and tested in the large towing tank and seakeeping basin of the China Ship Scientific Research Centre, Wuxi, China, in order to measure the six-degrees-of-freedom forces, moments and motions at forward speed in waves of different directions. Measurements are compared with predictions, and the comparison is generally good for the longitudinal motions thus verifying the analysis. For the transverse motions, acceptable discrepancies exist due to the non-inclusion in the analysis of rudder forces and viscous damping, and due differences in structural inertia properties between the physical model and the corresponding data used in the analysis. The inclusion of viscous damping in the time domain involves complex analysis and this problem is left to a future research.
基金The project supported by the National Natural Science Foundations of China the LNM,Institute of Mechanics,Academia Sinica
文摘A new hybrid model, which is based on domain decomposition and proposed by the authors is used for calculating the flow around a circular cylinder at low and middle Keulegan-Carpenter numbers (Kc=2～18)respectively.The vortex motion patterns in asymmetric regime,single pair(or transverse)regime and double pair(or diagonal)regime are successfully simulated.The calculated drag and inertial force coefficients are in better agreement with experimental data than other recent computational results.
