摆动水翼的推力与流场结构数值研究

在一定的Reynolds数范围内,水生动物和微型仿生机械通常采用摆动的方式获得推力,这种摆动可以用行进波来表示,行进波的波长则描述了摆动生物的柔性．该文用浸入边界方法模拟了低Reynolds数情况下,水翼NACA-65-010在水中摆动时的流场．结果表明,水翼摆动产生推力的大小与行进波波长密切相关,随着波长的增大,推力系数减小,推进效率则在一定的波长值达到最大;推力的产生与两种流场结构有关:即反Krmn涡街和涡对,摆动水翼后缘尾迹中形成反Krmn涡街时产生的推力要大于尾迹中形成涡对产生时的推力．     

Stability of a supersonic flat-plate wake (Comparison of numerical and experimental results)

The stability of the wake downstream of a plat plate with a blunt trailing edge is numerically investigated at a supersonic freestream velocity. The calculated stability characteristics are compared with the experimental data.     

Evolution of Artificial Perturbations in the Boundary Layer on a Plate and in Its Wake at Supersonic Free-Stream Velocity

The evolution of artificial perturbations in the boundary layer on the flat section of a plate, on the backward-facing wedge behind the rarefaction wave fan, and in the wake is studied experimentally at the Mach number M=2.     

H3+团簇离子与固体相互作用

报道了H3+团簇通过碳膜对产生的各种产物的测量结果.分析讨论了三原子离子团簇与固体相互作用中的电荷交换过程.证明在产物的形成中,电荷交换过程起关键作用.分析研究了H3+团簇与固体作用中的团簇效应和尾流效应. 关键词： H3+团簇 电荷交换 团簇效应 尾流效应     

互相关测速的误差综合分析

为了提高互相关技术在实验中测量结果的准确性和可信度,本文对产生误差的各种原因进行了分析,并对误差进行了估算.通过探讨相应的解决方法，提出了一种针对互相关测速误差的综合分析及其相应处理手段.     

Dynamical mode decomposition of Gurney flap wake flow

The present work uses dynamic mode decomposition (DMD) to analyze wake flow of NACA0015 airfoil with Gurney flap. The physics of DMD is first introduced. Then the PIV-measured wake flow velocity field is decomposed into dynamical modes. The vortex shedding pattern behind the trailing edge and its high-order harmonics have been captured with abundant information such as frequency, wavelength and convection speed. It is observed that high-order dynamic modes convect faster than low-order modes; moreover the wavelength of the dynamic modes scales with the corresponding frequency in power law.     

氘氢混合气体的高频离子源中H2D+与D+2的比例实测研究

分子离子H2D+在天体物理和天体化学研究中有重要意义,但在实验研究中不可避免混入D+2从而对实验结果产生影响.本文采取产物对比与分析的方法,将离子源中两种离子的比例实际测量出来,从而能较为准确地研究H2D+的结构和性质.将实验测量的结果与理论推算进行比较,得到了相对较好的结果.本文所采用的方法将对类似的研究提供有益的借鉴和启发.     

An experimental study on the effects of relative rotation direction on the wake interferences among tandem wind turbines

An experimental study was conducted to investigate the effects of relative rotation direction on the wake interferences among two tandemwind turbines models.While the oncoming flow conditions were kept in constant during the experiments,turbine power outputs,wind loads acting on the turbines,and wake characteristics behind the turbines were compared quantitatively with turbine models in either co-rotating or counter-rotating configuration.The measurement results reveal that the turbines in counter-rotating would harvest more wind energy from the same oncoming wind,compared with the co-rotating case.While the recovery of the streamwise velocity deficits in the wake flows was found to be almost identical with the turbines operated in either co-rotating or counter-rotating,the significant azimuthal velocity generated in the wake flow behind the upstream turbine is believed to be the reason why the counter-rotating turbines would have a better power production performance.Since the azimuthal flow velocity in the wake flow was found to decrease monotonically with the increasing downstream distance,the benefits of the counter-rotating configuration were found to decrease gradually as the spacing between the tandem turbines increases.While the counter-rotating downstream turbine was found to produce up to 20%more power compared with that of co-rotating configuration with the turbine spacing being about 0.7D,the advantage was found to become almost negligible when the turbine spacing becomes greater than 6.5D.It suggests that the counter-rotating configuration design would be more beneficial to turbines in onshore wind farms due to the smaller turbine spacing(i.e.,~3 rotor diameters for onshore wind farms vs.~7 rotor diameters for offshore wind farms in the prevailing wind direction),especially for those turbines sited over complex terrains with the turbine spacing only about 1–2 rotor diameters.     

飞行器尾涡对的不稳定性建模

为了确定飞行器尾流的保持距离和诱导失稳运动性质,首先在一阶近似Biot-Savart定律的基础上,推导了任意多个涡对的诱导运动模型,进而利用线性组合方法得到涡系诱导运动的对称以及反对称模态,并结合模态矩阵特征值的性质描述对称分布涡系的稳定性.因为尾涡结构的不稳定性依赖于相应的模态矩阵特征值的取值,所以在利用对称分布的二涡对的模态验证所推导的模态矩阵理论的正确性的基础上,进一步给出了三涡对的模态矩阵对应的失稳模态.理论推导和特征值的计算显示随着涡丝数量的不断增加,三涡系的不稳定性增强,并且涡系对扰动的放大作用增强.     

利用尾流效应确定HD2+的结构与核间距

在研究HD2+ 与固体膜的相互作用时, 发现在HD2+ 穿过固体时产生了较强的尾流效应, 并在确定HD2+作的结构时, 尾流效应起到了关键的作用. 这一技术的使用, 可以使得许多使用传统方法无法确定的分子离子结构寻求到一种方法和手段. 本文就如何使用尾流效应来确定HD2+ 结构作一报道. 这种方法的基本思想是,库仑爆炸能谱图普相对于分子离子的核间距时非常是非常敏感的.