In this article, the overset grid assembly method is improved to efficiently solve several critical problems that occur when applying overset grids to the complicated geometries and moving body. First, instead of usin...In this article, the overset grid assembly method is improved to efficiently solve several critical problems that occur when applying overset grids to the complicated geometries and moving body. First, instead of using the two-step searching (i.e. cut and paste), a single-step searching method based on the grid cell size is proposed to modify holes and optimize the grid overlapping automatically. Second, discrepancies between the wall surface representations, where the grids overlap, are handled by introducing the wall's normal directions to the hole-map and projecting the interpolated points on the recipient mesh into the donor mesh. Finally, the dynamic overset method is modified to address the complex moving body problem. At every time step, the initial hole surface of the previous time step is dynamically adjusted to accomplish hole cutting and avoid the time consuming hole-map procedure. Numerical experiments show that the enhanced overset grid assembly method obtains satisfactory results.展开更多
A surrogate-model-based aerodynamic optimization design method for cycloidal propeller in hover was proposed,in order to improve its aerodynamic efficiency,and analyze the basic criteria for its aerodynamic optimizati...A surrogate-model-based aerodynamic optimization design method for cycloidal propeller in hover was proposed,in order to improve its aerodynamic efficiency,and analyze the basic criteria for its aerodynamic optimization design.The reliability and applicability of overset mesh method were verified.An optimization method based on Kriging surrogate model was proposed to optimize the geometric parameters for cycloidal propeller in hover with the use of genetic algorithm.The optimization results showed that the thrust coefficient was increased by 3.56%,the torque coefficient reduced by 12.05%,and the figure of merit(FM)increased by 19.93%.The optimization results verified the feasibility of this design idea.Although the optimization was only carried out at a single rotation speed,the aerodynamic efficiency was also significantly improved over a wide range of rotation speeds.The optimal configuration characteristics for micro and small-sized cycloidal propeller were:solidity of 0.2-0.22,maximum pitch angle of 25°-35°,pitch axis locating at 35%-45% of the blade chord length.展开更多
为了更真实地模拟机翼副翼受控偏转运动,以二维带副翼的机翼为例,运用动态重叠网格技术耦合求解受比例—积分—微分(proportional integral derivative,PID)反馈控制的副翼偏转过程中的非定常NS(navier-stokes)方程,获取了副翼偏转过程...为了更真实地模拟机翼副翼受控偏转运动,以二维带副翼的机翼为例,运用动态重叠网格技术耦合求解受比例—积分—微分(proportional integral derivative,PID)反馈控制的副翼偏转过程中的非定常NS(navier-stokes)方程,获取了副翼偏转过程中的流场特性。首先利用动态重叠网格求解算法和Fluent软件包模拟了NACA0012翼型的定常气动特性和非定常气动特性,然后利用动态重叠网格求解算法对受PID控制的二维机翼副翼偏转过程进行了数值模拟。结果表明,该数值模拟方法可靠有效,能够为控制算法的设计提供参考,并能够反映副翼受控运动的非定常流场时序变化,初步建立了二维机翼副翼受控运动模拟与机翼流场求解相结合的直接数值模拟方法,为更真实地模拟运动物体的流场特性提供了一种动态求解算法。展开更多
运用双时间推进法和动态嵌套网格技术对扰动风作用下的多段翼型非定常绕流进行了数值模拟.首先,结合预处理技术对麻省理工学院(Massachusetts Institude of Technology,MIT)的翼型模型在扰动风作用下的流动进行数值模拟,并运用其实验结...运用双时间推进法和动态嵌套网格技术对扰动风作用下的多段翼型非定常绕流进行了数值模拟.首先,结合预处理技术对麻省理工学院(Massachusetts Institude of Technology,MIT)的翼型模型在扰动风作用下的流动进行数值模拟,并运用其实验结果验证程序的正确性;然后,对多段翼型在周期性的扰动风作用下的非定常粘性绕流进行数值模拟,得到非定常情况下气动力随扰动风变化的迟滞规律.计算范围内的结果表明:扰动风的频率越低,幅度越大,多段翼型整体上的气动力越大;扰动风的频率越高,幅值越大,对多段翼型的气动力影响越大.展开更多
基金National Natural Science Foundation of China (90716010)
文摘In this article, the overset grid assembly method is improved to efficiently solve several critical problems that occur when applying overset grids to the complicated geometries and moving body. First, instead of using the two-step searching (i.e. cut and paste), a single-step searching method based on the grid cell size is proposed to modify holes and optimize the grid overlapping automatically. Second, discrepancies between the wall surface representations, where the grids overlap, are handled by introducing the wall's normal directions to the hole-map and projecting the interpolated points on the recipient mesh into the donor mesh. Finally, the dynamic overset method is modified to address the complex moving body problem. At every time step, the initial hole surface of the previous time step is dynamically adjusted to accomplish hole cutting and avoid the time consuming hole-map procedure. Numerical experiments show that the enhanced overset grid assembly method obtains satisfactory results.
基金Project supported by the National Natural Science Foundation of China(5137912551490675+3 种基金114320095157914511272120)the Chang Jiang Scholars Program of China(T2014099)~~
文摘A surrogate-model-based aerodynamic optimization design method for cycloidal propeller in hover was proposed,in order to improve its aerodynamic efficiency,and analyze the basic criteria for its aerodynamic optimization design.The reliability and applicability of overset mesh method were verified.An optimization method based on Kriging surrogate model was proposed to optimize the geometric parameters for cycloidal propeller in hover with the use of genetic algorithm.The optimization results showed that the thrust coefficient was increased by 3.56%,the torque coefficient reduced by 12.05%,and the figure of merit(FM)increased by 19.93%.The optimization results verified the feasibility of this design idea.Although the optimization was only carried out at a single rotation speed,the aerodynamic efficiency was also significantly improved over a wide range of rotation speeds.The optimal configuration characteristics for micro and small-sized cycloidal propeller were:solidity of 0.2-0.22,maximum pitch angle of 25°-35°,pitch axis locating at 35%-45% of the blade chord length.
文摘为了更真实地模拟机翼副翼受控偏转运动,以二维带副翼的机翼为例,运用动态重叠网格技术耦合求解受比例—积分—微分(proportional integral derivative,PID)反馈控制的副翼偏转过程中的非定常NS(navier-stokes)方程,获取了副翼偏转过程中的流场特性。首先利用动态重叠网格求解算法和Fluent软件包模拟了NACA0012翼型的定常气动特性和非定常气动特性,然后利用动态重叠网格求解算法对受PID控制的二维机翼副翼偏转过程进行了数值模拟。结果表明,该数值模拟方法可靠有效,能够为控制算法的设计提供参考,并能够反映副翼受控运动的非定常流场时序变化,初步建立了二维机翼副翼受控运动模拟与机翼流场求解相结合的直接数值模拟方法,为更真实地模拟运动物体的流场特性提供了一种动态求解算法。
文摘运用双时间推进法和动态嵌套网格技术对扰动风作用下的多段翼型非定常绕流进行了数值模拟.首先,结合预处理技术对麻省理工学院(Massachusetts Institude of Technology,MIT)的翼型模型在扰动风作用下的流动进行数值模拟,并运用其实验结果验证程序的正确性;然后,对多段翼型在周期性的扰动风作用下的非定常粘性绕流进行数值模拟,得到非定常情况下气动力随扰动风变化的迟滞规律.计算范围内的结果表明:扰动风的频率越低,幅度越大,多段翼型整体上的气动力越大;扰动风的频率越高,幅值越大,对多段翼型的气动力影响越大.
