In this paper,we studied the wing root pivot joint’s radial load of a submersible airplane which imitates the locomotion of gannet’s Morus plunge-diving,by implementing a test device name Mimic-Gannet.The housing of...In this paper,we studied the wing root pivot joint’s radial load of a submersible airplane which imitates the locomotion of gannet’s Morus plunge-diving,by implementing a test device name Mimic-Gannet.The housing of the device was designed by mimicking the morphology of a living gannet,and the folding wings were realized by the mechanism of variable swept back wing.Then,the radial loads of the wing root were obtained under the conditions of different dropping heights,different sweptback angles and different water-entry inclination angles(i.e.,the angle between the longitudinal body axis and the water surface),and the relationships between the peak radial load and the above three parameters were analyzed and discussed respectively.In the studied areas,the minimum peak radial load of the pivot joint is 50.93 N,while the maximum reaches up to1135.00 N.The largest peak load would be generated for the situation of vertical water entry and zero wing sweptback angle.And it is of great significance to choose the three parameters properly to reduce the pivot joint’s radial load,i.e.,larger wing sweptback angle,smaller dropping height and water-entry inclination angle.It is also concluded that the peak radial load on the wing root is closely linear with the water-entry dropping height and the wing sweptback angle with a significant correlation.Eventually,the relationship between the wing load and the dropping height,water-entry inclination angle or wing sweptback angle,could be used to calculate the wing load about plunge-diving of a submersible aircraft,and the conclusions reveal the wing load characteristic of the gannet’s plunge process for the biologists.展开更多
A method for static aeroelastic trim analysis and flight loads computation of a flexible aircraft with large deformations has been presented in this paper,which considers the geometric nonlinearity of the structure an...A method for static aeroelastic trim analysis and flight loads computation of a flexible aircraft with large deformations has been presented in this paper,which considers the geometric nonlinearity of the structure and the nonplanar effects of aerodynamics.A nonplanar vortex lattice method is used to compute the nonplanar aerodynamics.The nonlinear finite element method is introduced to consider the structural geometric nonlinearity.Moreover,the surface spline method is used for structure/aerodynamics coupling.Finally,by combining the equilibrium equations of rigid motions of the deformed aircraft,the nonlinear trim problem of the flexible aircraft is solved by iterative method.For instance,the longitudinal trim analysis of a flexible aircraft with large-aspect-ratio wings is carried out by both the nonlinear method presented and the linear method of MSC Flightloads.Results obtained by these two methods are compared,and it is indicated that the results agree with each other when the deformation is small.However,because the linear method of static aeroelastic analysis does not consider the nonplanar aerodynamic effects or structural geometric nonlinearity,it is not applicable as the deformations increase.Whereas the nonlinear method presented could solve the trim problem accurately,even the deformations are large,which makes the nonlinear method suitable for rapid and efficient analysis in engineering practice.It could be used not only in the preliminary stage but also in the detail stage of aircraft design.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.51005008)
文摘In this paper,we studied the wing root pivot joint’s radial load of a submersible airplane which imitates the locomotion of gannet’s Morus plunge-diving,by implementing a test device name Mimic-Gannet.The housing of the device was designed by mimicking the morphology of a living gannet,and the folding wings were realized by the mechanism of variable swept back wing.Then,the radial loads of the wing root were obtained under the conditions of different dropping heights,different sweptback angles and different water-entry inclination angles(i.e.,the angle between the longitudinal body axis and the water surface),and the relationships between the peak radial load and the above three parameters were analyzed and discussed respectively.In the studied areas,the minimum peak radial load of the pivot joint is 50.93 N,while the maximum reaches up to1135.00 N.The largest peak load would be generated for the situation of vertical water entry and zero wing sweptback angle.And it is of great significance to choose the three parameters properly to reduce the pivot joint’s radial load,i.e.,larger wing sweptback angle,smaller dropping height and water-entry inclination angle.It is also concluded that the peak radial load on the wing root is closely linear with the water-entry dropping height and the wing sweptback angle with a significant correlation.Eventually,the relationship between the wing load and the dropping height,water-entry inclination angle or wing sweptback angle,could be used to calculate the wing load about plunge-diving of a submersible aircraft,and the conclusions reveal the wing load characteristic of the gannet’s plunge process for the biologists.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11172025,91116005)the Research Fund for the Doctoral Program of Higher Education of China (Grant No.20091102110015)
文摘A method for static aeroelastic trim analysis and flight loads computation of a flexible aircraft with large deformations has been presented in this paper,which considers the geometric nonlinearity of the structure and the nonplanar effects of aerodynamics.A nonplanar vortex lattice method is used to compute the nonplanar aerodynamics.The nonlinear finite element method is introduced to consider the structural geometric nonlinearity.Moreover,the surface spline method is used for structure/aerodynamics coupling.Finally,by combining the equilibrium equations of rigid motions of the deformed aircraft,the nonlinear trim problem of the flexible aircraft is solved by iterative method.For instance,the longitudinal trim analysis of a flexible aircraft with large-aspect-ratio wings is carried out by both the nonlinear method presented and the linear method of MSC Flightloads.Results obtained by these two methods are compared,and it is indicated that the results agree with each other when the deformation is small.However,because the linear method of static aeroelastic analysis does not consider the nonplanar aerodynamic effects or structural geometric nonlinearity,it is not applicable as the deformations increase.Whereas the nonlinear method presented could solve the trim problem accurately,even the deformations are large,which makes the nonlinear method suitable for rapid and efficient analysis in engineering practice.It could be used not only in the preliminary stage but also in the detail stage of aircraft design.
