国外大型风力机技术的新进展北大核心CSCD

为更好地了解国外大型风力机技术,促进国内大型风力机的发展,对近年来国外大型风力机设计技术的革新做出一个较为综合的评述.不仅涵盖陆上水平轴风力机,也将评述海上漂浮式风力机、垂直轴风力机、高空风力机以及带加速罩的风力机等技术的新进展.评述包括设计原理、经济效益、环境影响等综合评估因素,力求对新技术做出较为完整的解释.     

风力机风洞试验技术及研究进展北大核心CSCD

以UAE phase VI和MEXICO(model experiment in controlled conditions)项目以及中国空气动力研究与发展中心(China aerodynamics research and development center,CARDC)相关的研究工作为背景,概述了近年来风力机流场测量、压力分布测量、测力等风洞试验技术的进展,介绍了在风洞的影响、叶素的等效远场自由来流条件确定、三维旋转效应、动态入流效应、流场结构和诱导效应方面的重要研究成果.文章还简介了CARDC的大型风力机风洞试验研究工作及一些思路.     

“大型(兆瓦级)风力机的空气动力学问题”专刊预告

近年来,风能作为无污染、可再生的自然能源引起了人们的高度重视。风力机是捕获风能的动力装置。大型(兆瓦级)风力机的建造和运行涉及到一系列复杂的空气动力学理论和应用问题:如叶片翼型升力特性、叶片气动弹性和气动噪声、风力机风洞模拟实验以及叶片气动优化设计等,成为近期国内外力学、工程界研究的前沿和热点之一。     

大型近海水平轴风力机转轮的空气动力学性能优化判据

以近海风能工程为研究目标,对具有不同特性参数（设计风速、叶尖线速度和转轮实度）的大容量（1～10 MW）风力机转轮的气动性能与几何特性进行分析与研究．首先提出大型机组转轮气动性能优化判据:在其直径最小的前提下具有尽可能高的年可用风能特性因数以及与之相关的风能利用系数,因而可捕获最多风能,使年发电量最大．接着给出影响它的几个主要气动参数,如转轮设计风速、叶尖线速度以及转轮实度,并分析风力机在近海气象条件下运转时上述两个气动指标随这些参数变化的规律．提供的气动分析方法及结果可作为大型近海风力机转轮气动性能的评价基础．     

计算流体力学在大型风力机空气动力学的应用进展北大核心CSCD

针对大型风力机设计中的关键空气动力学问题,比较系统地介绍了计算流体力学(computational fluid dynamics,CFD)方法的主要应用,特别是在大型风力机翼型气动分析、风力机流动的数值模拟、风轮空气动力特性的数值计算以及大型风力机叶片的多目标气动优化设计方面的进展.基于CFD方法分别实现了风力机翼型与叶片二维/三维气动特性的准确预测,风力机尾流场涡系结构的准确捕捉;并结合多目标遗传算法对1.5 MW风力机叶片进行了优化,获得了具有高风能利用效率的叶片方案.     

基于系统动力学煤矿事故风险耦合度量研究

煤矿事故频发一直都是困扰中国煤炭安全生产的瓶颈,虽然近年来煤矿安全状况有所好转,但重特大事故仍时有发生.然而煤矿事故的产生不仅是由单一因素引起的,而是涉及到多个因素之间的耦合作用而导致的.首先,根据参与要素的不同,从同质与异质角度来研究煤矿事故风险耦合作用成因,并提出煤矿事故风险成因之间的因果关系图;其次,建立煤矿事故的非线性系统动力学动态耦合模型对煤矿事故风险成因耦合作用进行度量.最后,以王楼煤矿2014年1-12月份数据为例,利用该模型进行风险耦合度量比较分析.结果表明:在该煤矿事故风险耦合中,人的因素参与的风险耦合造成的耦合值最大,而由客观因素造成耦合要比主观因素造成的更难把握.     

一个刚柔耦合的火箭发射架动力学模型

对刚柔耦合火箭发射架进行了动力学建模．将火箭发射架分成两个子系统,一个是多刚体系统,另一个是空间大位移运动的柔性发射管．先对这两个子系统的动力学分别建模,然后再考虑这两个系统之间的动力学耦合,从而获得整个系统的动力学模型．这种方法把复杂系统离散成简单系统,再由现存的简单系统的动力学模型组合成整个系统的动力学模型,使得整个建模过程高效、方便．     

大位移Timoshenko转轴三维耦合动力学分析

对于高速柔性转轴,综合考虑滑移、弯曲、剪切变形、旋转惯性、陀螺效应和动不平衡等因素,运用Timoshenko旋转梁理论,给出弹性体空间运动的一般性描述,通过Hamilton原理建立弯曲-扭转-轴向三维耦合非线性动力学方程,应用参数摄动方法和假设振型方法进行化简,并用数值模拟分析了轴向刚性滑移、剪切变形、截面尺寸和转速等因素对转轴动力学响应的影响。     

C-L方法及其在工程非线性动力学问题中的应用

C-L方法可以揭示非线性振动系统的分岔特性,它结合对称性和奇异性理论并将Liapunov-Schmidt(简称LS)约化方法推广到非自治系统.作为应用实例,分析了非线性转子动力学低频振动分岔失稳问题的机理及其控制.     

求解动力学问题的普遍方法

本文阐明了标准化的Routh方程[1]的应用,给出了求解系统动力学问题的约束反力及运动状态变化的普遍方法,并给出了相应的矩阵方程。     

Advanced Control Design for Wind Turbines

In this contribution, the concept of a general design platform for control system of wind turbines is proposed. Different models of wind turbine systems are summarized, a novel control strategy for wind turbine control is proposed as a general platform for control system design. Simulation results are presented demonstrating the success of the proposed control method based on one of the chosen models for the design platform. A benchmark model (NREL) is chosen for the platform in order to adjust the control system design. Finally, the design process of control system based on the general platform is given and explained. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Floating Body Problems in Two Dimensions

Stanislav Ulam asked if the sphere is the only object floating in neutral equilibrium in every orientation and a negative answer was provided recently. Here, several related problems are discussed. The same question is asked for two-dimensional objects whose centroid is pinned and it is demonstrated that the answer is similar to the case of freely floating bodies. We also discuss the minimal number of equilibria of homogenous planar floating objects (either freely or with pinned centroid) representing duals of Ulam's Floating Body Problem. The nonexistence of shapes with less than four equilibria is proven in special cases including infinitesimal perturbations of a circle, however the general question remains open. The paper is complemented with remarks on analogous problems in three dimensions; connections to the family of Four-Vertex theorems are also pointed out.     

Investigations of Passive Flow Control Devices for Vertical Axis Wind Turbines

The purpose of these investigations is to study the possibilities to improve performances of a typical vertical axis wind turbines (VAWT), of Darrieus-type, using passive devices (mounted “on” or “inside” the blades of VAWT) to control dynamic flow separation (dynamic stall phenomenon). The passive devices considered for investigations are the Gurney flap, the slot or thin channel, and the turbulence promoters. Studies are performed numerically using computational fluid dynamics and where it is possible the results are compared with existent experimental or numerical data. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

水中悬浮隧道的空间曲线结构运动方程

借助参考直线坐标系,求解空间曲线结构在曲线坐标系中的几何方程．运用Hamilton原理推导空间螺旋曲线梁结构的运动方程．方程表明空间曲线结构4个自由度相互耦合,当结构退化为平面曲线结构时,两个相互垂直平面内的各自由度相互耦合．空间任意曲线梁结构的动力方程均可按照该文推导思路得出．对于水中悬浮隧道结构,可以忽略转动动能对振动的影响．     

Cauchy矩阵及其相关的插值问题

用复分析和矩阵方程理论给出C auchy矩阵求逆公式的一种新证明.作为应用,研究与H erm ite-C auchy矩阵相关的N evan linna-P ick插值问题,给出该插值问题全部解的简洁表示.     

Non-Commutative Harmonic Oscillators and Related Problems

This paper is mainly meant to be a survey on the state-of-the-art of the understanding we have of a family of systems with polynomial coefficients, called non-commutative harmonic oscillators (NCHOs), that has shown itself to be very rich in structure. The study of this family has required, and is requiring, the study of problems arising from different parts of Mathematics, from spectral theory to the theory of modular forms, just to mention a few of them. On the side of new results, they will be concerned with the creation-annihilation relations for NCHOs and with Fredholm properties of operators belonging to certain global Weyl-Hörmander classes, of which NCHOs are a particular case.     

三叶片垂直轴水轮机结构动力响应分析

提出采用改进离散涡和几何精确梁理论混合方法对三叶片垂直轴水轮机进行结构动力响应分析.相比传统的有限元方法,该方法具有求解速度快、建模简单、计算精确等优点.在模态分析中,计算了不同叶片高度下,水轮机叶片和整体的前五阶固有频率,分析了水轮机半径大小和叶片高度对固有频率的影响,结果显示:随着尺寸的增加,叶片和整体固有频率显著减小,整体固有频率更易受到半径大小的影响.在瞬态分析中,考虑了离心载荷和叶片的水动力载荷,得到在工作状况下,旋转一周过程中叶片的最大变形曲线;分析了在不同H/R（叶片高度和半径的比值）的情况下的叶片强度问题,结果显示:当H/R大于3.0时,叶片强度将会失效.     

On the Bessel Distribution and Related Problems

This article investigates basic properties of the Bessel distribution, a power series distribution which has not been fully explored before. Links with some well-known distributions such as the von Mises-Fisher distribution are described. A simulation scheme is also proposed to generate random samples from the Bessel distribution. This scheme is useful in Bayesian inferences and Monte Carlo computation.