Numerical simulation of wing stall of a blended flying wing configuration at transonic speed was conducted using both delayed detached eddy simulation（DDES） and unsteady Reynolds-averaged Navier-Stokes（URANS） equa...Numerical simulation of wing stall of a blended flying wing configuration at transonic speed was conducted using both delayed detached eddy simulation（DDES） and unsteady Reynolds-averaged Navier-Stokes（URANS） equations methods based on the shear stress transport（SST） turbulence model for a free-stream Mach number 0.9 and a Reynolds number 9.6 × 10. A joint time step/grid density study is performed based on power spectrum density（PSD） analysis of the frequency content of forces or moments, and medium mesh and the normalized time scale0.010 were suggested for this simulation. The simulation results show that the DDES methods perform more precisely than the URANS method and the aerodynamic coefficient results from DDES method compare very well with the experiment data. The angle of attack of nonlinear vortex lift and abrupt wing stall of DDES results compare well with the experimental data. The flow structure of the DDES computation shows that the wing stall is caused mainly by the leeward vortex breakdown which occurred at x/x= 0.6 at angle of attack of 14°. The DDES methods show advantage in the simulation problem with separation flow. The computed result shows that a shock/vortex interaction is responsible for the wing stall caused by the vortex breakdown. The balance of the vortex strength and axial flow, and the shock strength, is examined to provide an explanation of the sensitivity of the breakdown location. Wing body thickness has a great influence on shock and shock/vortex interactions, which can make a significant difference to the vortex breakdown behavior and stall characteristic of the blended flying wing configuration.展开更多
The stall flutter characters of high-aspect-ratio composite wing are investigated, and the effects of structure geometric nonlinearity and stiffness couple created by composite anisotropy on them also are discussed. F...The stall flutter characters of high-aspect-ratio composite wing are investigated, and the effects of structure geometric nonlinearity and stiffness couple created by composite anisotropy on them also are discussed. Firstly, the high-aspect-ratio wing is modeled as a composite thin-walled closed section Euler beam whose displacement and rotation both could be of finite value, and the nonlinear dynamic equations is build up on it with all the effects of geometric nonlinearity, aerodynamic nonlinearity and anisotropy of material being considered. Then vibration equations are deduced through perturbing the dynamic equations at wing＇s equilibrium position, and coupled with unsteady stall aerodynamic model and ONERA model, to obtain the nonlinear stall flutter analysis equations of wing. Finally, the flutter stabilities with various wind speeds are determined by the harmonic balance method. With several exampies, the validity of the stall flutter model is proved, and the significant effects of geometric nonlinearity on the stall flutter various characters as wall as the effects of ply angle on the stall flutter speed and frequency also are discussed.展开更多
通过在三角翼上游加入干扰圆柱的风洞实验方法，研究了来流干扰对微小型飞行器MAV（Micro Air Vehicle）气动特性的影响．结果表明，在刚性和弹性三角翼顶点上游加入圆柱干扰时，两者均出现缓失速，刚性翼产生缓失速与干扰圆柱尾流关系...通过在三角翼上游加入干扰圆柱的风洞实验方法，研究了来流干扰对微小型飞行器MAV（Micro Air Vehicle）气动特性的影响．结果表明，在刚性和弹性三角翼顶点上游加入圆柱干扰时，两者均出现缓失速，刚性翼产生缓失速与干扰圆柱尾流关系密切，弹性翼的缓失速不仅与此有关，还与弹性翼的振动有关．无干扰或在机翼顶点加入干扰时，在攻角为4^o～18^o内弹性翼的升力系数比刚性翼的要大，但升阻比相对要小．由于弹性翼的振动与机翼绕流结构、气动力之间的耦合，弹性翼顶点与翼尖振动的主频随着攻角增大呈规律性的变化，失速攻角附近翼尖的振动主频是其涡脱落频率．展开更多
基金supported by the National Natural Science Foundation of China (No. 11372337)
文摘Numerical simulation of wing stall of a blended flying wing configuration at transonic speed was conducted using both delayed detached eddy simulation（DDES） and unsteady Reynolds-averaged Navier-Stokes（URANS） equations methods based on the shear stress transport（SST） turbulence model for a free-stream Mach number 0.9 and a Reynolds number 9.6 × 10. A joint time step/grid density study is performed based on power spectrum density（PSD） analysis of the frequency content of forces or moments, and medium mesh and the normalized time scale0.010 were suggested for this simulation. The simulation results show that the DDES methods perform more precisely than the URANS method and the aerodynamic coefficient results from DDES method compare very well with the experiment data. The angle of attack of nonlinear vortex lift and abrupt wing stall of DDES results compare well with the experimental data. The flow structure of the DDES computation shows that the wing stall is caused mainly by the leeward vortex breakdown which occurred at x/x= 0.6 at angle of attack of 14°. The DDES methods show advantage in the simulation problem with separation flow. The computed result shows that a shock/vortex interaction is responsible for the wing stall caused by the vortex breakdown. The balance of the vortex strength and axial flow, and the shock strength, is examined to provide an explanation of the sensitivity of the breakdown location. Wing body thickness has a great influence on shock and shock/vortex interactions, which can make a significant difference to the vortex breakdown behavior and stall characteristic of the blended flying wing configuration.
文摘The stall flutter characters of high-aspect-ratio composite wing are investigated, and the effects of structure geometric nonlinearity and stiffness couple created by composite anisotropy on them also are discussed. Firstly, the high-aspect-ratio wing is modeled as a composite thin-walled closed section Euler beam whose displacement and rotation both could be of finite value, and the nonlinear dynamic equations is build up on it with all the effects of geometric nonlinearity, aerodynamic nonlinearity and anisotropy of material being considered. Then vibration equations are deduced through perturbing the dynamic equations at wing＇s equilibrium position, and coupled with unsteady stall aerodynamic model and ONERA model, to obtain the nonlinear stall flutter analysis equations of wing. Finally, the flutter stabilities with various wind speeds are determined by the harmonic balance method. With several exampies, the validity of the stall flutter model is proved, and the significant effects of geometric nonlinearity on the stall flutter various characters as wall as the effects of ply angle on the stall flutter speed and frequency also are discussed.
文摘通过在三角翼上游加入干扰圆柱的风洞实验方法，研究了来流干扰对微小型飞行器MAV（Micro Air Vehicle）气动特性的影响．结果表明，在刚性和弹性三角翼顶点上游加入圆柱干扰时，两者均出现缓失速，刚性翼产生缓失速与干扰圆柱尾流关系密切，弹性翼的缓失速不仅与此有关，还与弹性翼的振动有关．无干扰或在机翼顶点加入干扰时，在攻角为4^o～18^o内弹性翼的升力系数比刚性翼的要大，但升阻比相对要小．由于弹性翼的振动与机翼绕流结构、气动力之间的耦合，弹性翼顶点与翼尖振动的主频随着攻角增大呈规律性的变化，失速攻角附近翼尖的振动主频是其涡脱落频率．
