Wave forerunners of streamwise structures in a swept wing boundary layer

In a model experiment wave packets (forerunners) have been detected for the first time in the flow regions preceding the fronts of streamwise structures in a swept wing boundary layer. The characteristics of the wave packets and the generating streamwise structures and the dynamics of their downstream development are investigated. It is shown that the forerunners can transform into turbulent spots thus leading to laminar-turbulent transition. Certain components of the forerunners are compared with a periodic instability wave.     

Investigation on vortex shedding of a swept-back wing

Effects of Reynolds number and angle of attack on the vortex shedding of a finite swept-back wing are experimentally studied. The cross-sectional profile of the wing is NACA 0012, and the sweep-back angle is 15° The time series signals detected by hot-wire in the wake region shows four distinct behaviors: laminar, subcritical, transitional, and supercritical. The derived Strouhal number curves are significantly different in these four behaviors. In addition, the statistical properties of turbulence, that is, the power spectrum density function, probability density function, correlation coefficient, Lagrangian integral time scales, and length scales are also presented in this paper.     

Application of a vortex lattice numerical model in the calculation of inviscid incompressible flow around delta wings

The flow over a flat plate delta wing at incidence and in sideslip is studied using vortex lattice models based on streamwise penelling. For the attached flow problem the effect of sideslip is simulated by modifying the standard vortex lattice model for zero sideslip by aligning the trailing vortices aft of the wing along the resultant flow direction. For the separated flow problem a non-linear vortex lattice model is developed for both zero and non-zero sideslip angles in which the shape and position of the leading edge separation vortices are calculated by an iterative procedure starting from an assumed initial shape. The theoretical values are compared with available theoretical and experimental results.     

Finite Element Modelling of Moored Vessels

In this paper, we develop a new finite element model for a cable suspended in water. Global existence and uniqueness of solutions of the truncated system is shown for a slightly simplified equation describing the motion of a cable with negligible added mass and supported by fixed end-points. Based on this, along with well known results on local existence and uniqueness of solutions for symmetrizable hyperbolic systems, we conjecture a global result for the initial-boundary value problem. The FEM model for the cable is assembled to give a model of a multi-cable mooring system, which, in turn, is coupled to a rigid body model of the floating vessel. The result is a coupled dynamical model of a moored vessel, which can be applied to applications such as turret-based moored ships, or tension leg platforms.     

牛顿运动定律和机翼举力

将空气简化为理想流体，由牛顿运动定律推出气体做曲线运动时的切向伯努利方程和法向压强梯度表达式，并解释了机翼举力。     

机翼变形的双激光器实时测量原理

在飞机机身的上下位置分别安装一个激光器,提出了一种实时测量在飞行过程中机翼弹性变形量的方法。以激光器与安装反射镜的机翼顶端之间的测量距离数据为依据,得到机翼或机身上任意点的实时变形量。机翼或机身上任意点的实时变形量是从机翼变形数据库中提取的数据量计算得到。根据弹性薄板理论,利用理想二维梁为例说明了该方法的实现过程,并且进行仿真说明。该方法对实时测量机翼弹性变形量具有普遍意义和实际应用价值。     

Time-resolved spectral wing emission kinetics and optical imaging of human cancerous and normal prostate tissues

Time-resolved polarization-dependent kinetics of near infrared (NIR) spectral wing (SW) emission from human cancerous and normal prostate tissues was investigated. The differences between the temporal profiles, intensities and polarization properties of SW emission from cancerous and normal prostate tissues were observed. The intensity of SW emission from cancerous prostate tissue at peak position was found ∼2 times stronger than the normal prostate tissue indicating changes of fluorophores contained in the cancerous tissue compared with normal tissue. The decay time of anisotropy of SW emission from cancerous tissue was found ∼1.4 times longer than that of normal tissue reflecting changes of the micro-environment of fluorophores in the cancerous tissue as compared with the normal tissue. The stronger intensity of SW emission from cancerous tissue was used to image and identify cancerous areas surrounded by normal tissue.     

晶体电子在稳恒磁场中的能谱与有效质量近似的适用性

晶体电子在稳恒磁场中的能谱是具有无穷嵌套自相似结构的Ｈｏｆｓｔａｄｔｅｒ“蝴蝶”，在介绍该能谱的基础上对固体物理教材中采用有效质量近似分析回旋共振和德·哈斯－范·阿尔芬效应的适用性条件进行了分析。     

Microstructures and Optical Properties of Scales of Butterfly Wings

This paper describes the mechanism generating the beautiful wing colors of various male butterflies and the relationship between the wing material and the color appearance. The microstructure of the scales covering the upper surface of the wings was analyzed with the aid of a scanning electron microscope. The basic mechanism of color generation of structurally colored scales is determined for the first time in accordance with the theory of optical interference in thin film layers using a model of wing scales. Optical properties were found in relation to the three-dimensional spectral reflectance of the samples, and differences were observed between the brightness perceived in subjective evaluations and calculated values based on the reflective spectra of the structurally colored wings. The results of this study suggest that the microroughness of the upper wing surface may influence the perceived gloss of structurally colored wings.