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171.
旋转状态气膜换热机理的数值研究 总被引:1,自引:1,他引:0
大涡模拟研究了旋转对单孔平板气膜冷却的影响,气膜出流的雷诺数为2600,吹风比为0.5,计算了静止和旋转数为0.02两种状态的流动和换热,从湍流结构演化的角度讨论了旋转状态气膜换热的机理.结果表明:①发卡涡是决定气膜换热的主要湍流结构,旋转状态发卡涡的形状和运动规律主要受哥氏力的影响;②气膜在哥氏力作用下向高半径方向偏... 相似文献
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174.
给出一个新的向量恒等式,首先采用函数论方法严格证明了该恒等式,其次从向量分析角度指出该恒等式与向量加法的三角形法则之间的密切联系,最后从质量守恒的观点给出该恒等式的一种物理解释。 相似文献
175.
Ideal proportional navigation (IPN) is a natural choice for exoatmospheric interception for its mighty capture capability and ease of implementation. The closed-form solution of two- dimensional ideal proportional navigation was conducted in previous public literature, whereas the practical interception happens in the three-dimensional space. A novel set of relative dynamic equations is adopted in this paper, which is with the advantage of decoupling relative motion in the instantaneous rotation plane of the line of sight from the rotation of this plane. The dimension-reduced IPN is constructed in this instantaneous plane, which functions as a three-dimensional guidance law. The trajectory features of dimension-reduced IPN are explored, and the capture regions of dimension-reduced IPN with limited acceleration against nonmaneuvering and maneuvering targets are analyzed by using phase plane method. It is proved that the capture capability of IPN is much stronger than true proportional navigation (TPN), no matter the target maneuvers or not. Finally, simulation results indicate that IPN is more effective than TPN in exoatmospheric interception scenarios. 相似文献
176.
Previous research has shown that training can improve mental rotation performance and has found connections between mental and manual rotation. Here we examine how practice in mental or manual (virtual) rotation, affects performance on mental and manual rotation tasks, compared to a control condition. Experiment 1 examined improvement on a mental rotation task following practice in mental or manual rotation. Both mental and manual rotation practice led to more efficient posttest performance. Experiment 2 examined improvement on a manual rotation task. Practice in manual but not mental rotation led to improved performance. Analyses of the manual rotation trajectories revealed no evidence of strategy differences. These results suggest that manual rotation may require additional processes outside of those needed for mental rotation. In terms of training effects, manual rotation training improved both manual and mental rotation performance, whereas mental rotation only significant improved mental rotation performance. 相似文献
177.
曲率对旋转态气膜冷却效率影响的数值模拟 总被引:1,自引:0,他引:1
通过对旋转状态下曲率叶片模型上气膜冷却现象的流动和换热进行数值模拟,得到了不同主流雷诺数、吹风比和旋转数情况下吸力面和压力面上的冷却效率分布.计算选用κ-ω和SST(Shear-Stress Transport)湍流模型,主流雷诺数Re=3 198.4~6 716.6,吹风比M=0.2~1.2,旋转数Rt=0~0.015 9.结果表明:旋转数的增大导致气膜孔下游中心区域的冷却效率下降,但使压力面整场的冷却效果略有提高;吹风比的增大使得吸力面和压力面上的冷却效率逐渐降低,主流雷诺数的变化对壁面整体冷却效果则影响不大.此外,相同工况下吸力面上的冷却效率要高于压力面上的对应值. 相似文献
178.
给出了一种通过静态电阻应变仪及外旋式粘度装置测量流体粘度的方法。由同步电动机带动外圆筒旋转剪切流体,从而将粘性力传递给内筒,内筒与圆轴相连。粘性力产生的扭矩使圆轴产生应变,在圆轴表面黏贴电阻应变片,通过合理组桥将应变显示在静态电阻应变仪上,根据应力应变关系计算出扭矩,从而计算出流体的动力粘度。 相似文献
179.
Junwei Zhao 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(6):838-845
Time–distance helioseismology is one of the local helioseismology techniques that are used to derive the interior properties of the Sun. It has been used to study the structures and flow fields beneath sunspots on local scales, as well as used to derive interior rotational rates and meridional flow velocities on global scales. In addition to the efforts in improving time–distance measurements and inversions, theoretical modeling is also carried out to enhance the accuracy of sensitivity kernels. Recently, by use of realistic numerical simulation on solar convection, we have also started to investigate the validity of time–distance studies. 相似文献
180.
本文根据Y-12飞机在一次试飞中偶然发生的突然下俯、双发停车相快速旋转等现象,按照飞机姿态变化的先后顺序进行了分析、讨论和研究,解开了一次空中遇险之谜. 相似文献