This article deals with real-time hi-fi simulation of large aircraft flying in turbulent wind in a simulator to study its takeoff and landing behavior in microburst wind shear. A parameterized three-dimensional （3D）...This article deals with real-time hi-fi simulation of large aircraft flying in turbulent wind in a simulator to study its takeoff and landing behavior in microburst wind shear. A parameterized three-dimensional （3D） microburst model is built up on the basis of vortex ring and Rankine vortex principle. Complicated microburst wind fields are simulated by means of vortex ring declination and multi-vortex superposition. Based on the modeling data of Boeing 747-100, a dynamic model with wind shear effects considered is established and a general method to modify the aerodynamic model is proposed. A controller for longitudinal and lateral escapes is designed and verified in simulated microburst wind field. Results indicate that, with high extensibility, reasonability and effectiveness, the 3D microburst model with wind shear effects considered is fit to simulate real wind fields. Different escape schemes can be adopted to fly through a wind field from different locations. The model can be used for real-time flight simulation in a flight simulator.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
The author establishes a large deviation for k-dimensional Brownian motion B in stronger topology, by which the functional modulus of continuity for B in Holder norm can be obtained.
We prove a moderate deviation principle for a super-Brownian motion with immigration of all dimensions, and consequently fill the gap between the central limit theorem and large deviation principle.
The flow over a backward-facing step(BFS)is a typical separation and reattachment flow.Its flow structures and unsteady mechanisms are still not well explored.In this paper,the global velocity fields of a BFS are obta...The flow over a backward-facing step(BFS)is a typical separation and reattachment flow.Its flow structures and unsteady mechanisms are still not well explored.In this paper,the global velocity fields of a BFS are obtained by a synchronous particle image velocimetry(PIV)system with Reh=5345(Reynolds number)and Er=2(expansion ratio).Flow structures are distinguished and defined by the fraction of the negative velocity(upn).The reattachment zone(Lr)is quantitatively defined as(u0.9,u/0.1)on the bottom wall.Spatial distribution of the large-scale vortices couples well with the divided flow structures and their temporal evolution presenting four stages(forming,developing,shedding and redeveloping)when travel downstream.The unsteady motions with various low frequencies are well explained by the coherent vortices and flow structures.Among the unsteady low frequency motions,the Kelvin Helmholtz(KH)vortices and the oscillation of Xr(OX)come likely from the free shear layer.The KH vortices contribute to the unsteadiness of the temporal flow,and the OX is the primary response to the vortical fluctuations.展开更多
基金Foundation item： Program of National Natural Science Foundation of China and The Civil Aviation （60776812）
文摘This article deals with real-time hi-fi simulation of large aircraft flying in turbulent wind in a simulator to study its takeoff and landing behavior in microburst wind shear. A parameterized three-dimensional （3D） microburst model is built up on the basis of vortex ring and Rankine vortex principle. Complicated microburst wind fields are simulated by means of vortex ring declination and multi-vortex superposition. Based on the modeling data of Boeing 747-100, a dynamic model with wind shear effects considered is established and a general method to modify the aerodynamic model is proposed. A controller for longitudinal and lateral escapes is designed and verified in simulated microburst wind field. Results indicate that, with high extensibility, reasonability and effectiveness, the 3D microburst model with wind shear effects considered is fit to simulate real wind fields. Different escape schemes can be adopted to fly through a wind field from different locations. The model can be used for real-time flight simulation in a flight simulator.
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.
文摘The author establishes a large deviation for k-dimensional Brownian motion B in stronger topology, by which the functional modulus of continuity for B in Holder norm can be obtained.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.10071008 and 10121101).
文摘We prove a moderate deviation principle for a super-Brownian motion with immigration of all dimensions, and consequently fill the gap between the central limit theorem and large deviation principle.
基金Project supported by the National Natural Science Foundation of China(Grant No.51909169)The Science and Technology Support Program of Jiangsu Province(Grant No.SBK2019042181)+1 种基金the Guizhou Science and Technology Cooperation Support((2017)2865)the International S&T Cooperation Program of China(Grant No.2015DFA01000).
文摘The flow over a backward-facing step(BFS)is a typical separation and reattachment flow.Its flow structures and unsteady mechanisms are still not well explored.In this paper,the global velocity fields of a BFS are obtained by a synchronous particle image velocimetry(PIV)system with Reh=5345(Reynolds number)and Er=2(expansion ratio).Flow structures are distinguished and defined by the fraction of the negative velocity(upn).The reattachment zone(Lr)is quantitatively defined as(u0.9,u/0.1)on the bottom wall.Spatial distribution of the large-scale vortices couples well with the divided flow structures and their temporal evolution presenting four stages(forming,developing,shedding and redeveloping)when travel downstream.The unsteady motions with various low frequencies are well explained by the coherent vortices and flow structures.Among the unsteady low frequency motions,the Kelvin Helmholtz(KH)vortices and the oscillation of Xr(OX)come likely from the free shear layer.The KH vortices contribute to the unsteadiness of the temporal flow,and the OX is the primary response to the vortical fluctuations.
