Monte-Carlo Simulation of Multiple-Molecular-Motor Transport

Multimotor transport is studied by Monte-Carlo simulation with consideration of motor detachment from the filament. Our work shows, in the case of low load, the velocity of multi-motor system can decrease or increase with increasing motor numbers depending on the single motor force-velocity curve.The stall force and run-length reduced greatly compared to other models.Especially in the case of low ATP concentrations, the stall force of multi motortransport even smaller than the single motor's stall force.     

壁板颤振的分析模型、数值求解方法和研究进展

研究壁板颤振问题需要计及大挠度变形下结构的几何非线性效应,不仅涉及气动弹性稳定性,而且关心结构的非线性颤振响应.该文回顾了飞行器壁板颤振问题的国内外研究情况,评述了在壁板颤振研究中采用的分析模型、数值求解方法以及在理论分析和试验方面的研究成果,并提出了今后壁板颤振问题的4个研究方向.      

Limit Cycle Oscillations of a Wing Section with a Tip Mass

This paper presents an investigation into the limit cycleoscillation phenomenon for a nonlinear aeroelasticsystem under unsteady aerodynamics. The system consists of a sweptbackwing section carrying a tip mass with one degree of freedom. Thejunction stiffness considered between the wing and the tip mass istrilinear. The method of harmonic balance, which can be very practicalin the study of nonlinear flutter, is used for the theoretical analysisof limit cycle oscillations. Stable, unstable and semi-stable limitcycles are predicted in the system for both cases of hardening andsoftening springs. Results found by numerical simulation provide theamplitudes of limit cycles. The experimental results in wind tunneltests agree well with the predictions obtained both theoretically andnumerically.     

翼型厚度对气动弹性特性的影响

结合基于$k$-$\omega$的SST两方程湍流模型,求解雷诺平 均Navier-Stokes方程获得定常和非定常气动力,耦合翼型弹性运动方程,在时间 域内模拟了不同厚度对称翼型在不同迎角下的气动弹性动态过程, 并重点研究了较大迎角下的不同厚度翼型流场特征和气动弹性的性质,研究结果表明：在论 文所涉及的参数情况下,对于迎角从零到大迎角范围,翼型颤振临界速度随迎角的变化不是 单调的. 翼型颤振临界速度迅速下降的起始迎角比最大升力系数对应的迎角小很多.     

Numerical modelling of the stability of loaded shells of revolution containing fluid flows

A mixed finite-element algorithm is proposed to study the dynamic behavior of loaded shells of revolution containing a stationary or moving compressible fluid. The behavior of the fluid is described by potential theory, whose equations are reduced to integral form using the Galerkin method. The dynamics of the shell is analyzed with the use of the variational principle of possible displacements, which includes the linearized Bernoulli equation for calculating the hydrodynamic pressure exerted on the shell by the fluid. The solution of the problem reduces to the calculation and analysis of the eigenvalues of the coupled system of equations. As an example, the effect of hydrostatic pressure on the dynamic behavior of shells of revolution containing a moving fluid is studied under various boundary conditions. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 2, pp. 185–195, March–April, 2008     

带有结构非线性的跨音速翼型颤振特性研究

以非定常N-S方程为主管方程,采用时间推进的方法,计算翼型振荡的瞬态非定常气动力,并与带有结构非线性的颤振方程耦合求解,计算了带有结构刚度非线性(间隙型,三次型刚度非线性)和结构阻尼非线性(三次型阻尼非线性)的结构响应特性和颤振特性.计算研究表明,由于同时具有结构和气动非线性,振荡极限环和气动力极为复杂.     

桥梁颤振气动导数在均匀流与紊流作用下的统一辨识理论研究

桥梁断面颤振气动导数的准确识别是桥梁空气动力稳定性研究的基础,一直是桥梁风工程研究领域的前沿课题。基于工况模态分析理论,本文首先导出了紊流条件下桥梁颤振气动导数辨识的完整方法;其次,将上述数据处理方式运用到由均匀流条件引起的自由衰减振动中,得出与紊流情况类似的结果。本文提出的方法能够用同样的辨识原理、同一个数据处理程序统一地对紊流和均匀流下的桥梁气动导数进行辨识;最后,利用数值仿真算例验证上述理论。     

超音速气流中受热壁板的稳定性分析

采用Galerkin方法建立二维壁板的非线性气动弹性运动方程,用一阶活塞理论模拟壁板 受到的气动力. 基于李雅普诺夫间接法分析了平壁板的稳定性,得到了壁板失稳的边界 曲线;采用牛顿迭代法分析了壁板的屈曲变形,进而分析了后屈曲状态下壁板的稳定性; 在时域中分析了后屈曲状态下壁板的颤振边界. 分析结果表明,为了保证计算精度, 在二维壁板的静态失稳及过屈曲变形分析中,至少要取二阶谐波模态;在平壁板的超音速颤 振(动态失稳)边界分析中至少应取四阶模态. 还对壁板的温升,壁板长厚比、壁板密 度和气流马赫数作了无量纲变参分析,研究了这些参数的变化对壁板稳定性的影响规律. 研 究中发现,当气流速压较低时壁板一般会稳定在低阶谐波模态的屈曲变形位置,但是如果系 统出现多个渐近稳定的不动点,即使作用在壁板上的气流速压很低,壁板也有可能在较低速 压下发生二次失稳型颤振.     

Numerical investigations on the dynamic behavior of a 2-DOF airfoil in the transitional Re number regime based on fully coupled simulations relying on an eddy-resolving technique

The paper is the numerical counterpart of the experimental investigation on the fluid–structure interaction (FSI) of a wing with two degrees of freedom (DOF), i.e., pitch and heave. Wood et al. (2020) has provided the experimental basis by studying the flutter stability of an elastically mounted straight wing (NACA 0012 airfoil) in a wind tunnel considering the transitional Reynolds number regime. Three different configurations with varying distances between the fixed elastic axis and the variable center of gravity were considered. Additional free-oscillation tests in still air were carried out in order to make the mechanical properties of the setup available for the simulations. The present contribution describes the numerical methodology applied consisting of a partitioned coupled solver combining eddy-resolving large-eddy simulations on the fluid side with a solver for the governing equations of the translation and rotation of the rigid wing. In order to prove the parameters provided by the experiment and to determine the pure material damping coefficients not available from the measurements, simulations of 1-DOF free-oscillation tests in still air are carried out and analyzed. For validation purposes the corresponding 2-DOF free-oscillation tests in still air are assessed and a good agreement with the experimental data is achieved. Finally, the wing exposed to a constant free-stream of varying strength is analyzed leading to the characterization of complex instantaneous FSI phenomena such as limit-cycle oscillations and flutter. Under full utilization of the supplementary measurements the predictions are evaluated in detail. Contrary to the experiments the simulations provide the entire fluid data and unique data for the translatory and rotatory movement allowing to investigate the causes of the observed phenomena. Both limit-cycle oscillations and flutter can be reproduced by the coupled FSI predictions.     

微喷气提高轴流压气机稳定性的研究

在动叶顶部采用稳态微量喷气可以在不影响低速轴流压气机的稳态工作特性下,拓宽其工作范围。为了分析微喷气作用机理,进行了一系列不同喷气结构的实验研究,包括不同喷气角,不同喷嘴安装位置以及不同喷气量.利用高频响动态传感器测量叶尖间隙动态压力谱,分析表明微量喷气可以改变叶尖顶部泄漏涡的轨迹.