Controlling aerodynamic characteristics of airfoils by means of periodic pulsed energy supply

The possibility of controlling the aerodynamic characteristics of lifting airfoils by means of local periodic pulsed energy supply in transonic flight regimes has been studied. Using a numerical solution of two-dimensional nonstationary equations of gasdynamics, a change in the flow structure near a symmetric airfoil is determined as dependent on the amount of energy supplied to the lower side of the airfoil in a range of attack angles.     

Nonlinear effects in the interaction of periodic pulsed energy supply and shock-wave structure during transonic streamlining of wing profiles

We have evaluated the possibility of controlling the aerodynamic characteristics of wing profiles by means of a local periodic pulsed energy supply in transonic flight regimes. The influence of the energy supply rate and the position and area of the zone of energy supply on the flow structure near a symmetric wing profile and on the wave drag has been studied using a numerical solution of two-dimensional nonstationary equations of gasdynamics. The energy supply in front of the breakdown shock wave within extended zones in the immediate vicinity of the streamlined contour leads to a significant decrease in the wave drag of a given wing profile. The nature of this phenomenon is elucidated and it is established that there exists a limiting rate of energy supply.     

Control of the aerodynamic characteristics of wing airfoils by nonstationary energy supply in transonic flow

The possibility of controlling the aerodynamic characteristics of wing airfoils in transonic regimes of flight using one-sided pulse-periodic energy supply has been studied. The flow structure near the symmetric airfoil at different angles of attack and its aerodynamic characteristics as functions of the value of energy in its nonsymmetric (about the airfoil) supply have been determined by numerical solution of two-dimensional nonstationary gasdynamic equations. A comparison of the obtained results and the data of calculation of flow past the airfoil at different angles of attack without energy supply has been made. It has been established that a prescribed lift can be obtained, using energy supply, with a much higher fineness ratio of the airfoil than that in the case of flow past it at an angle of attack. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 82, No. 1, pp. 18–22, January–February, 2009.     

Nonstationary flow in a channel with variable cross section under conditions of periodic pulsed energy supply

The effect of a periodic pulsed supply of energy, equal to that of hydrogen combustion in air, on the structure of a supersonic flow in a channel of variable cross section modeling a ramjet tract has been studied. The flow has been numerically simulated based on two-dimensional gasdynamic equations. Various flow regimes are obtained depending on the configuration of energy supply zones and the excess air ratio in the channel.     

Effect of axial curvature on aerodynamic characteristics of planar channels

The effect of axial curvature on average characteristics of a turbulent flow of incompressible liquid in the gap between two coaxial cylinders is studied.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 37, No. 1, pp. 65–71, July, 1979.     

Influence of a periodic pulsed energy source on the regime of supersonic flow past a body

A two-dimensional nonstationary problem on the interaction of a trace developed behind a periodic pulsed energy source and a body occurring in a supersonic flow is considered. The results of numerical calculations are compared to the available experimental data.     

高速列车风阻制动风翼抗鸟撞分析

对研制的复合材料高速列车风阻制动风翼建立有限元模型。据接触-碰撞基本理论利用非线性动力分析软件LS-DYNA对鸟撞制动风翼过程数值仿真,将计算结果与实验数据对比验证仿真过程的合理性。结果显示,该制动风翼能承受500 km/h鸟体撞击,极限能达625 km/h,满足要求设计。鸟撞过程中制动风翼变形具有冲击波传递特征,应力峰值主要出现在被撞击区域,与底座相连部分及摇臂附近也会出现应力集中。     

Resonant interaction of periodic pulsed energy source with shock-wave structure in transonic flow past airfoil

The interaction of a periodic pulsed energy source with a closing shock wave that arises near an airfoil in transonic flight regimes has been studied. The evolution of the shock-wave structure near a symmetric airfoil is analyzed based on a numerical solution of two-dimensional nonstationary equations of gasdynamics. A resonance interaction mechanism is established that leads to a significant (by an order of magnitude) decrease in the wave drag of the airfoil.     

银杏树叶的气动特性研究

对影响银杏树叶在风载荷作用下振动变形以及临界状态发生的改变进行研究.通过对180片树叶进行风洞实验,发现银杏树叶的叶片角与叶片凹痕是影响树叶振动变形与临界风速的重要因素.同时还发现银杏树叶最终稳定时的阻力系数随着叶片角度的增大而减小,叶片角较大的树叶在相同风速下,具有更多的稳定状态与更好的保持自身稳定的能力.凹痕长度不同的银杏叶片其临界风速也各不相同.     

Focusing and spectral characteristics of periodic diffractive optical elements with circular symmetry under femtosecond pulsed illumination

The analytical solution is derived, within the Rayleigh-Sommerfeld formulation of diffraction, for the on-axis spectral irradiance of a broadband source after diffracting through a circular symmetric hard aperture. By using this solution, and within the paraxial approximation, we investigate several diffraction-induced effects originated by binary diffractive optical elements made up of a set of annular apertures with equal areas and periodic in the squared radial coordinate. In particular, the ability to focus femtosecond pulses is investigated. In addition, the analysis of the spectral modifier function associated with these elements allows us to simulate spectral shifts at focus positions. Finally, we introduce a relatively simple and low-cost technique to slice the spectrum of a broadband source in order to generate narrow bands or wavelength channels.     

Effect of discontinuity size on the energy absorption of structural steel beam profiles

The effect of size discontinuities on the energy absorption performance of squared steel profiles is reported. Finite element simulations of the compression strength of profiles with discontinuities, placed at mid span of the steel profiles in two opposite walls, were carried out. Circular and elliptical forms of the discontinuities were evaluated. Energy absorption capabilities were increased up to 12.54% and the peak load value was decreased to 10.52% with respect to the same structure without discontinuities. A buckling effect is observed in structures with discontinuities, which contributes to reducing the peak value while the energy absorbing characteristics decrease.     

鹅掌楸树叶气动特性研究

通过摄像统计实验以及风洞天平测力实验来研究真实鹅掌楸树叶气动特性,发现在风洞中随着风速的增加,当达到临界风速时,鹅掌楸树叶会发生状态突变,最后出现形状重构现象;真实鹅掌楸树叶反面作为迎风面时相对于正面作为迎风面时更为稳定;真实鹅掌楸树叶在来流方向的阻力系数随着雷诺数的增加趋近于0.1.     

波浪形圆柱的气动力特性试验研究

斜拉索的风荷载和风致振动问题突出,探索能够减阻抑振的新型斜拉索意义重大.研究表明,波浪形圆柱在Re=103～ 104有减阻抑振效果,而真实斜拉索的雷诺数通常在105量级,有必要研究波浪形圆柱在高雷诺数下的气动性能.以特定几何参数的波浪形圆柱为研究对象,通过风洞试验方法,研究了波浪形圆柱在Re=1.4×105～4.0×1...     

典型损伤对复合材料机翼振动特性的影响

利用大型商用软件MSC.Patran建立了某型无人机复合材料机翼的有限元模型。在机翼中分别模拟了蒙皮分层、蒙皮与翼梁翼肋脱粘以及翼梁裂纹这3种典型损伤,通过与无损伤复合材料机翼固有振动频率进行比较,分析了损伤位置和大小对机翼振动特性的影响。结果表明:3种典型损伤一般不会引起机翼各阶振动模态的改变,但会使各阶振动频率发生变化;对各阶振动频率的影响既与损伤位置有关,也与主承力结构的损伤程度有关;蒙皮分层和翼梁裂纹出现在机翼根部时对机翼振动频率的影响最明显。     

平板耦合颤振过程中气动能量转换特性

基于分步分析思路对耦合颤振运动方程进行解耦,通过引入考虑阻尼影响的初始运动方程,建立了结构-气流系统颤振能量机理的分析框架。结合平板风洞试验研究了颤振发生过程中系统内主要气动能量的变化规律。研究结果表明在平板耦合颤振过程中联合气动导数数A1*H3*建立了能量在两个自由度上传递的途径,并且在颤振发生过程中由于扭转振动和竖向振动的相位差逐渐减小,使得该联合气动导数对系统的输能能力不断增强。扭转气动阻尼是系统的主要耗能项,并且耗能能力与导数A2*的数值密切相关而与相位差没有关系。扭转气动刚度在一个振动周期内对系统能量几乎没有贡献,对耦合颤振的影响很小。     

Investigation of aerodynamic characteristics of manganese ore

The results of an investigation of the aerodynamic characteristics of manganese ore, ready for delivery from the pit and sorted out in fractions, are presented for the humidity range 1.3 to 8.5%. The formulas for computing the pressure drop in the bed, the velocity of start of fluidization, and the velocity of entrainment of the particles are also given.     

Numerical calculation of pulsed laser deposited film profiles

Pulsed laser deposition (PLD) is a straightforward method for production of the widest variety of materials, especially multicomponent oxides, in the form of thin film. One of the particular advantages of this technique, the possibility of control of film composition, is ensured by applying (reactive) atmospheres of pressures up to tenths of millibars.