高速铁路接触网系统气动弹性模型风洞试验研究

为研究高速铁路接触网系统的风振特性,按照气动弹性模型相似理论建立5柱4跨接触网系统的气动弹性模型,并进行其风洞试验;采用加速度传感器、激光位移计以及三维动态激光位移计,分别测量腕臂结构的加速度、位移以及接触线三维动态位移,研究均匀流场（试验风速级数范围为3~14m·s-1）和紊流度为20%的紊流场（试验风速级数范围为2~8m·s-1）条件下风攻角为90°和60°时,接触网系统腕臂结构和接触线不同位置的风振响应。结果表明：相同风速下,接触线在紊流场中的位移响应大于在均匀流场的响应;风攻角对接触网挂线点和接触线的影响不同,相比较而言,60°风攻角对挂线点更为不利,而90°风攻角对接触线更为不利;同一吊弦区段内接触线跨中的3点风偏位移基本相同。

气动弹爆破过程性能仿真分析

针对工业界对于安全有效的管道清洁装置的需求,设计了一种利用气动爆破的原理进行管道除垢的设备.该装置采用气动控制,利用压缩空气的瞬时释放产生的射流与冲击波的能量击碎管道内壁的附着物,实现管道除垢.通过分析装置工作的原理及运行过程,给出了重要参数的建模过程.通过仿真分析了气爆过程中压强、剪切力的分布特点以及传播过程,计算了其管道内气流速度场的分布变化,得出了气动弹爆破过程中对壁面产生的冲击主要来源于射流以及冲击波,并且在使用10MPa的工作压强下一次爆破可清理的管道范围超过160m.该设计可以高效的实现管道清污的作用.

IMPROVED ALGORITHM FOR CFD/CSD COUPLED SYSTEM DESIGN AND CALCULATION

The data information transfer and time marching strategies between computational fluid dynamics （CFD） and computational structural dynamics （CSD） play crucial roles on the aeroelastic analysis in a time domain. An improved CFD/CSD coupled system is designed, including an interpolation method and an improved loosely coupled algorithm. The interpolation method based on boundary element method （BEM） is developed to transfer aerodynamic loads and structural displacements between CFD and CSD grid systems, it can be universally used in fluid structural interaction solution by keeping energy conservation. The improved loosely coupled algo-rithm is designed, thus it improves the computational accuracy and efficiency. The new interface is performed on the two-dimensional （2-D） extrapolation and the aeroelastie response of AGARD445.6 wing. Results show that the improved interface has a superior accuracy.

Computations of Cross-Link Forces and Vibrations for the Test Bed of the Full Channel Gas

In order to control the cross? link forces and the vibration frequencies of the test bed of the full channel gas within the allowable ranges, the analyses of forces and deformation of the test bed was done, for the variously restrained elastic movable frame and the rigid one, the vibration frequencies were computed respectively by means of the methods of mechanics of materials, elasticity and vibration mechanics, the cross link forces and the vibration frequencies of the test bed were tested. The results of theoretical computation comparatively approach the experimental results. The computational methods could be used to availably estimate the design parameters relevant to the test bed of the full channel gas.

MULTI-BODY AEROELASTIC STABILITY ANALYSIS OF TILTROTOR AIRCRAFT IN HELICOPTER MODE

The muhi-body analysis of the aeroelastic stability of the tiltrotor aircraft is presented. Muhi-body dynamic differential equations are combined with the equations of the unsteady dynamic inflow model to establish the complete unsteadily aeroelastic coupling analytical model of the tiltrotor. The stability of the tiltrotor in the helicopter mode is analyzed aiming at a semi span soft-inplane tihrotor model with an elastic wing. Parametric effects of the lag stiffness of blades and the flight speed are analyzed. Numerical simulations demonstrate that the multibody analytical model can analyze the aeroelastic stability of the tiltrotor aircraft in the helicopter mode.

光纤光栅传感器在风洞测试中的应用探讨

光纤布喇格光栅是近些年新研制出来的一种用于测量应变、应力、温度等多个物理量的传感器，因其具有抗电磁干扰、灵敏渡高、尺寸小、重量轻等特点，已广泛应用到各个工程句强戋。本文介绍了光纤布喇格光栅传感器基本原理，通过光纤布喇格光栅传感器在航空航天与民用工程中的国内外应用状况来探讨其在风洞设备测试及风垌气动弹性试验中的应用前景。

Effect of viscoelasticity on nonlinear vibration of single microbubble

Based on the Church-Hoff model, the nonlinear oscillations of a single encapsulated microbubble with a finite thickness shell are theoretically studied. The effects of viscoelasticity on radial oscillations and the fundamental and harmonic components are researched. The peaks of radial oscillations and magnitudes of power spectra of the fundamental and harmonic components all increase gradually with the shear modulus of shell varying from 0 to 10 MPa by an interval of 0. 1 MPa at the same shear viscosity, while they decrease as the shear viscosity increases from 0 to 1 Pa · s by an interval of 0. 01 Pa · s at the same shear modulus. The fluctuation ranges of subharmonic and ultraharmonic signals are much larger than both the fundamental and second harmonic components. It means that the effect of viscoelasticity on the subharmonic and ultraharmonic signals is greater than that on the fundamental and second harmonic components. So adjusting the viscoelasticity of the shell is a potential method to obtain a perfect microbubble contrast agent used for the subharmonic and ultraharmonic imaging. Four points with significant fundamental and harmonic components are chosen as an example： a shear viscosity of 0. 39 Pa · s with shear modulus of 3.9, 6. 6, and 8.6 MPa, respectively; a shear modulus of 6.6 MPa with a shear viscosity of 0.42 Pa · s.

A Comparative Assessment of Aerodynamic Models for Buffeting and Flutter of Long-Span Bridges

Wind-induced vibrations commonly represent the leading criterion in the design of long-span bridges. The aerodynamic forces in bridge aerodynamics are mainly based on the quasi-steady and linear unsteady theory. This paper aims to investigate different formulations of self-excited and buffeting forces in the time domain by comparing the dynamic response of a multi-span cable-stayed bridge during the critical erection condition. The bridge is selected to represent a typical reference object with a bluff con- crete box girder for large river crossings. The models are viewed from a perspective of model complexity, comparing the influence of the aerodynamic properties implied in the aerodynamic models, such as aerodynamic damping and stiffness, fluid memory in the buffeting and self-excited forces, aerodynamic nonlinearity, and aerodynamic coupling on the bridge response. The selected models are studied for a windspeed range that is typical for the construction stage for two levels of turbulence intensity. Furthermore, a simplified method for the computation of buffeting forces including the aerodynamic admittance is presented, in which rational approximation is avoided. The critical flutter velocities are also compared for the selected models under laminar flow.

Wind-induced responses of super-large cooling towers

Traditional gust load factor(GLF)method,inertial wind load(IWL)method and tri-component method(LRC+IWL)cannot accurately analyze the wind-induced responses of super-large cooling towers,so the real combination formulas of fluctuating wind-induced responses and equivalent static wind loads(ESWLSs)were derived based on structural dynamics and random vibration theory.The consistent coupled method(CCM)was presented to compensate the coupled term between background and resonant response.Taking the super-large cooling tower(H=215 m)of nuclear power plant in Jiangxi Province,China,which is the highest and largest in China,as the example,based on modified equivalent beam-net design method,the aero-elastic model for simultaneous pressure and vibration measurement of super-large cooling tower is firstly carried out.Then,combining wind tunnel test and CCM,the effects of self-excited force on the surface pressures and wind-induced responses are discussed,and the wind-induced response characteristics of background component,resonant component,coupled term between background and resonant response,fluctuating responses,and wind vibration coefficients are discussed.It can be concluded that wind-induced response mechanism must be understood to direct the wind resistant design for super-large cooling towers.

Optimization of projectile aerodynamic parameters based on hybrid genetic algorithm

Aerodynamic parameters are important factors that affect projectile flight movement. To obtain accurate aerodynamic parameters, a hybrid genetic algorithm is proposed to identify and optimize the aerodynamic parameters of projectile. By combining the traditional simulated annealing method that is easy to fall into local optimum solution but hard to get global parameters with the genetic algorithm that has good global optimization ability but slow local optimization ability, the hybrid genetic algo- rithm makes full use of the advantages of the two algorithms for the optimization of projectile aerodynamic parameters. The simulation results show that the hybrid genetic algorithm is better than a single algorithm.

RESPONSEANDLOADSANALYSISOFHELICOPTERROTORWITHADVANCEDTIPSUSINGANEFFICIENTROTORWAKEMODELING

A comprehensive aeroelastic analysis of helicopter rotor with advanced tips based on finite element theory in space and time is coupled with an efficient rotor wake modeling. The effects of different wake models and tip sweep angles on blade response and loads are investigated in forward flight. Each blade is assumed to undergo flap bending, lag bending and elastic twist deflections. The blade response is calculated from nonlinear periodic equations using a finite element in time scheme. For induced inflow distributions on the rotor disk, a constant vorticity contour wake model is used. Results show that blade response and loads are sensitive to wake model and tip sweep angle, and the rotor wake analysis is important for capturing the harmonics of vertical hub loads, flap bending moments and low speed aerodynamic loadings.

Fluid-structure interaction of panel in supersonic fluid passage

Fluid-structure interaction of panel in supersonic fluid passage is studied with subcycling and spline interpolation based predict-correct scheme. The passage is formed with two parallel panels, one is rigid and the other is flexible. The interaction between fluid flows and flexible panel is numerically studied, mainly focused on the effect of dynamic pressure and distance between two parallel panels. Subcycling and spline interpolation based predict-correct scheme is utilized to combine the vibration and fluid analysis and to stabilize long-term calculations to get accurate results. It’s demonstrated that the flutter characteristic of flexible panel is more complex with the increase of dynamic pressure and the decrease of distance between two parallel panels. Via analyzing the propagation and reflection of disturbance in passage, it’s determined as a main cause of the variations.

Effects of static aeroelasticity on composite wing characteristics under different flight attitudes

Composite wing static aeroelasticity was analyzed through a loosely coupled method and the effects on composite wing characteristics under different flight attitudes were presented. Structural analysis and aerodynamic analysis were carried out through finite element method (FEM) software NASTRAN and computational fluid dynamics (CFD) software FLUENT, respectively. Correlative data transfer and mesh regenerate procedure were applied to couple the results of computational structure dynamics (CSD) and CFD. After static aeroelasticity analysis under different flight attitudes, it can be seen that lift increases with the increase of flight speed and the incremental value enlarges gradually in both rigid and elastic wings. Lift presents a linear increment relationship with the increase of attack angle when the flight speed is 0.4Ma or 0.6Ma, but nonlinear increment in elastic wing when flight speed is 0.8Ma. On the effect of aeroelasticity, the maximum of deformation increases with the increase of flight speed and attack angle, and the incremental value decreases with the increase of flight speed while uniform with different attack angles. The results provide a reference for engineering applications.

Wind tunnel study on wind-induced vibration of middle pylon of Taizhou Bridge

Full aero-elastic model tests are carried out to investigate wind-induced vibration of middle steel pylon of Taizhou Bridge. Model of the pylon under different construction periods is tested in both uniform and turbulent flow field. And the yaw angle of wind changes from transverse to longitudinal. Through full aero-elastic model testing, wind-induced vibration is checked, which includes vortex resonance, buffeting and galloping. Vortex resonance is observed and further studies are carried out by changing damping ratio. Based on wind tunnel testing results, wind-resistance of middle pylon is evaluated and some suggestions are given for middle pylon's construction.

Aeroelastic Simulation for Symmetric Manoeuvre of 123 Manager Light Plane

Expansion of computer technologies allow using numerical simulation in the early stages of aircraft design more and more often. The role of both wind tunnels and initial test flights used to verify the validity of solutions seems to be diminishing. Big systems for three-dimensional simulations of Fluid-Structure Interactions （FSI） constitute highly specialized and costly software. Most of the codes are based on many simplifications. In this paper fluid-structure interaction, taking into account the symetric manoeuvre of ultra light plane, is concerned. This phenomenon has important influence in many aeronautical applications. The method and developed system is demonstrated on ultra light I23 plane. For the first flow the comparison with experiment made in Institute of Aviation Warsaw is presented. Finally, aeroelastic simulation of full 123 aircraft configuration presents the capability of used numerical codes to analyze largescale complex geometries for manoeuvre. All computations were carried out in parallel environment for CFD mesh of order of millions tetrahedral elements.

Simulation of aerothermodynamics model on ballistic safety of fusible alloy fuze

In order to ensure the ballistic safety of fusible alloy fuze at reliable delay arming, melting point of fusible alloy needs to be calculated based on projectile velocity at safe time and distance. Taking shrapnel KZVD fuze of Switzerland oerlikon 2ZLa/353 35 mm double barrel self-propelled antiaircraft artillery as an example, based on the aerodynamics heating theory, the calculation of theory model and simulation of projectile head stagnation point temperature were done in initial stage of sim-plified exterior ballistic from engineering viewpoint when the initial projectile velocity was 1 175 m/s and the error was ±15 m/s. The melting point of fusible alloy in the safe distance was obtained by analyzing the temperature of projectile head stagnation point at corresponding projectile velocity. The simulated results indicate that the melting point of fusible alloy de-rived by theoretical calculation is identical with the result of simulation at the velocity range of 1 160 to 1 190 m/s. So the aero- thermodynamics model can be applied to design the fusible alloy fuze of corresponding melting point based on the requirement of safe distance. This method can be taken as the reference in studying the thermodynamic question of projectile flying at high speed.

CFD Investigation of Compressible Low Angles of Attack Flow over the Missile

In modem missile design, the operation of a missile aerodynamics with angles of attack is required to serve a demand on the maneuverability. The key aero-physics is the development of vortices and its interaction to the control surface such as wing and fins. This paper thus presents the investigation of the missile flow field at 4° and 8° degrees of angles of attack. The Mach numbers for both case were varied from 0.6 to 5.5. Here, the Steady Reynolds-Averaged Navier-Stokes （SRANS） equations with standard κ-ε turbulence model were selected. The numerical results of aerodynamics coefficients （both force and moment） were compared against semi-empirical data computed using Missile DatCOM. The results revealed the development of vortices observed and their interaction with fin at the rear part of the missile.

Model Order Reduction of Complex Airframes Using Component Mode Synthesis for Dynamic Aeroelasticity Load Analysis

Airframe structural optimization at different design stages results in new mass and stiffness distributions which modify the critical design loads envelop. Determination of aircraft critical loads is an extensive analysis procedure which involves simulating the aircraft at thousands of load cases as defmed in the certification requirements. It is computationally prohibitive to use a GFEM （Global Finite Element Model） for the load analysis, hence reduced order structural models are required which closely represent the dynamic characteristics of the GFEM. This paper presents the implementation of CMS （Component Mode Synthesis） method for the generation of high fidelity ROM （Reduced Order Model） of complex airframes. Here, sub-structuring technique is used to divide the complex higher order airframe dynamical system into a set of subsystems. Each subsystem is reduced to fewer degrees of freedom using matrix projection onto a carefully chosen reduced order basis subspace. The reduced structural matrices are assembled for all the subsystems through interface coupling and the dynamic response of the total system is solved. The CMS method is employed to develop the ROM of a Bombardier Aerospace business jet which is coupled with aerodynamic model for dynamic aeroelasticity loads analysis under gust turbulence. Another set of dynamic aeroelastic loads is also generated employing a stick model of same aircraft. Stick model is the reduced order modelling methodology commonly used in the aerospace industry based on stiffness generation by unitary loading application. The extracted aeroelastic loads from both models are compared against those generated employing the GFEM. Critical loads modal participation factors and modal characteristics of the different ROMs are investigated and compared against those of the GFEM. Results obtained show that the ROM generated using Craig Bampton CMS reduction process has a superior dynamic characteristics compared to the stick model.

Synergetic Optimization of Missile Shapes for Aerodynamic and Radar Cross-Section Performance Based on Multi-objective Evolutionary Algorithm

A multiple-objective evolutionary algorithm (MOEA) with a new Decision Making (DM) scheme for MOD of conceptual missile shapes was presented, which is contrived to determine suitable tradeoffs from Pareto optimal set using interactive preference articulation. There are two objective functions, to maximize ratio of lift to drag and to minimize radar cross-section (RCS) value. 3D computational electromagnetic solver was used to evaluate RCS, electromagnetic performance. 3D Navier-Stokes flow solver was adopted to evaluate aerodynamic performance. A flight mechanics solver was used to analyze the stability of the missile. Based on the MOEA, a synergetic optimization of missile shapes for aerodynamic and radar cross-section performance is completed. The results show that the proposed approach can be used in more complex optimization case of flight vehicles.

Unified Aerodynamic-Acoustic Formulation for Aero-Acoustic Structure Coupling

Conventional coupled BE/FE （Boundary-Element/Finite-Element） method and modeling of structural-acoustic interaction has shown its promise and potential in the design and analysis of various structural-acoustic interaction applications. Unified combined acoustic and aerodynamic loading on the structure is synthesized using two approaches. Firstly, by linear superposition of the acoustic pressure disturbance to the aeroelastic problem, the effect of acoustic pressure disturbance to the aeroelastic structure is considered to consist of structural motion independent incident acoustic pressure and structural motion dependent acoustic pressure, which is known as the scattering pressure, referred here as the acoustic aerodynamic analogy. Secondly, by synthesizing the acoustic and aerodynamic effects on elastic structure using an elegant, effective and unified approach, both acoustic and aerodynamic effect on solid structural boundaries can be formulated as a boundary value problem governed by second order differential equations which lead to solutions expressible as surface integral equations. The unified formulation of the acousto-aeroelastic problem is amenable for simultaneous solution, although certain prevailing situations allow the solution of the equations independently. For this purpose, the unsteady aerodynamic problem which was earlier utilizes well-established lifting surface method is reformulated using Boundary Element （BE） approach. These schemes are outlined and worked out with examples.