中国采用近似边界条件的振荡翼型欧拉方程数值解

This paper presents an efficient numerical method for solving the unsteady Euler equations on stationary Cartesian grids.Wall boundary conditions are implemented on nonmoving mean wall positions by assuming the airfoil being thin and undergoing small deformation,but the mean angle of attack of the body can still be large and we use the full nonlinear Euler equation in the field for accurate resolution of shock waves and vorticity.The method does not require the generation of moving body-fitted grids and thus can be easily deployed in any fluidstructure interaction problem involving relatively small deformation of a thin body.We use the first-order wall boundary conditions in solving the full Euler equation.Unsteady transonic flow is calculated about an oscillating NACA 0012 airfoil at free stream Mach number M∞=0. 755, mean angle of attack αm=0. 016,amplitude of pitching oscillation αo=2.51,reduced frequency k=0.0814.The computed results,including surface pressure distribution,instantaneous lift and moment coefficients are compared with known experimental data.It is shown that the first-order boundary conditions are satisfactory for airfoils of typical thicknesses with small deformation for unsteady calculations.     

Evaluation of Land-Use Efficiency Based on Regional Scale ——A Case Study in Zhanjiang, Guangdong Province

Evaluating land use efficiency is critical to the revision of general land use planning. An assessment indicator system for regional land use efficiency was established in this paper from the aspects of society, economy, ecology and environment. The weight of each indicator was defined by an analytical hierarchy process （AHP） and the entropy method （EM）. Then, a case study in Zhanjiang was carried out to analyze the regional land use efficiency from 1996 to 2004 and its development by using the method of multifactor composite evaluation and an analytical model of the degree of coordination. The results indicate that land use efficiency with respect to society and the economy improved, whereas the ecological and environmental efficiencies were found to decrease. The degree of coordination in Zhanjiang is still at the status of basic coordination. Finally, measures for enhancing the ecological and environmental establishment are suggested in order to improve the regulations of land use structure and patterns, establish ecological forests for the public good and green corridors and prevent the soil erosion.     

Analysis of Spatio-Temporal Changes of Land Usein Xuzhou City Based on Remote Sensing

1 Introduction Land use is the complete set of biological and technological activities which involve long-term or periodical land management for economic and social aims. Dynamic changes of land use essentially reflect the objective course that various categories of land use are being continually adjusted and planned in order to meet the needs of social and economic de- velopment. Research on dynamic changes is condu- cive to understanding the reasons and mechanism of changes in land use. The …     

Two new methods for power flow tracing using bus power balance equations

Two new methods were presented for power flow tracing（PFT）.These two methods were compared and the results were discussed in detail.Both methods use the active and reactive power balance equations at each bus in order to solve the tracing problem.The first method considers the proportional sharing assumption while the second one uses the circuit laws to find the relationship between power inflows and outflows through each line,generator and load connected to each bus of the network.Both methods are able to handle loop flow and loss issues in tracing problem.A formulation is also proposed to find the share of each unit in provision of each load.These methods are applied to find the producer and consumer＇s shares on the cost of transmission for each line in different case studies.As the results of these studies show,both methods can effectively solve the PFT problem.     

Numerical investigation of radial inflow in the impeller rear cavity with and without baffle

In typical small engines, the cooling air for high pressure turbine(HPT) in a gas turbine engine is commonly bled off from the main flow at the tip of the centrifugal impeller. The pressurized air flow is drawn radially inwards through the impeller rear cavity. The centripetal air flow creates a strong vortex because of high inlet tangential velocity, which results in significant pressure losses. This not only restricts the mass flow rate, but also reduces the cooling air pressure for down-stream hot components. The present study is devoted to the numerical modeling of flow in an impeller rear cavity. The simulations are carried out with axisymmetric and 3-D sector models for various inlet swirl ratio β_0(0–0.6), turbulent flow parameter lT(0.028–0.280) with and without baffle. The baffle is a thin plate attached to the stationary wall of the cavity, and is proved to be useful in reducing the pressure loss of centripetal flow in the impeller rear cavity in the current paper. Further flow details in impeller rear cavity with and without baffle are displayed using CFD techniques. The CFD results show that for any specified geometry, the outlet pressure coefficient of impeller rear cavity with or without baffle depends only on the inlet swirl ratio and turbulent flow parameter. Meanwhile, the outlet pressure coefficient of the cavity with baffle is indeed smaller than that of cavity without baffle, especially for the cases with high inlet swirl ratio. The suppression of the effect of centrifugal pumping and the mixing beween the main air which is downstream of the baffle and the recirculating flow of the vortex in the stationary cavity, which are caused by the use of baffle, are the underlying reasons that lead to the reduction of outlet pressure loss.     

Study on S-shaped characteristic of Francis reversible unit by on-site test and CFD simulation

The operation parameters (vibration, shaft displacement and pressure fluctuation) of No. 1 Francis reversible unit of Baoquan pumped-storage power station were measured on site in the no-load mode at net heads of 518.04, 522.01 and 530.38 m, respectively. The rotational speed fluctuations in the no-load mode at three net heads were beyond synchronization requirement with obvious S-shaped characteristic, and misaligned guide vanes (MGV) had to be put into use for synchronization. Further analysis demonstrated that the rotating frequency signal was generally dominant in vibration and shaft displacement mixing signal in the no-load mode, while the frequency domain was wide without an obvious main frequency in pressure fluctuation mixing signal. Besides, the SST k-ω turbulence model was adopted to simulate the four quadrant characteristic curves of Baoquan model pump-turbine at three gate openings, and the relative error between simulation results and model test data was within ±6%, indicating that the simulation method in this paper is feasible and S-shaped characteristic of the pump-turbine can be simulated with CFD method.     

Correlations Based on CFD and Their Applications in Optimization for Staggered and Parallel Plate Fin Heatsinks

Both parallel and staggered plate fin arrays have shown promise for use in high perfomance heatsinks regard of its individual manufacturing costs.The geomtrical and operational parameters are very important to theri cooling perfomance as heatsinks in practical applications.Fluent 5.0 commercial CFD(computational fluid dynamic)code is used to simulate the flow and heat transfer of those heatsinks of different realistic parameters.Based on those simulations,two correlations,concerning Nusselt number and friction factor as the functions of geometrical and operational parameters,FB(fin-base area ratio),PR( ratio of spanwise pitch to lengthwise pitch)and Re,were developed.From the both,the performance comparisons for optimizing geometrical and operational parameters of a fixed dimension heatsink are whown at constant umping power and constant thermal resistance.Several optimized parameters were obtained with the discussion to various goals in real application.It demonstrates that in some particular situations,the parallel plate fin heatsinkds can out perform the staggered ones.     

Quality Control of Recycled Aggregates Derived from Construction and Demolition Wastes

In 2007, over 24 million tons of Construction and Demolition (C&D) wastes were generated in Hong Kong. Since the local landfills will be saturated in about 6 years, it is important to find a viable way to reuse these waste materials as to alleviate the demand on public fill capacity. In order to tackle the problem, the Hong Kong government has set up a temporary recycling facility in Hong Kong in 2002 for producing different sizes of recycled aggregate for use in various construction materials. The Hong Kong Polytechnic University has been studying the feasible use of recycled aggregates in Hong Kong for a number of years. A substantial amount of experimental results on the properties of recycled aggregates and the effect of recycled aggregates on the properties of concrete and other construction products (e.g. concrete blocks and granular subbase) has been published. In this paper, the experience of Hong Kong in using recycled aggregates are summarized and a set of quality control guidelines proposed for governing the use of recycled aggregates in Hong Kong is introduced. The experience and guidelines may also be useful for the recycling of waste materials derived from the recent Sichuan earthquake in China.     

A method to manage the model base in DSS

How to manage and use models in DSS is a most important subject. Generally, it costs a lot of money and time to develop the model base management system in the development of DSS and most are simple in function or cannot be used efficiently in practice. It is a very effective, applicable, and economical choice to make use of the interfaces of professional computer software to develop a model base management system. This paper presents the method of using MATLAB, a well-known statistics software, as the development platform of a model base management system. The main functional framework of a MATLAB-based model base management system is discussed. Finally, in this paper, its feasible application is illustrated in the field of construction projects.     

CFD investigation and PIV validation of flow field in a compact return diffuser under strong part-load conditions

The internal flow fields in a compact return diffuser under strong part-load conditions are investigated both numerically and experimentally.For numerical simulation,three-dimensional unsteady Reynolds-Averaged Navier–Stokes equations are solved on high-quality structured grids in conjunction with the shear stress transport k–turbulence model by employing the computational fluid dynamics(CFD)software ANSYS-Fluent 14.5.For flow field measurements,a special test rig is designed and the two-dimensional particle image velocimetry(PIV)measurements are conducted in the diffuser midplane to capture the complex flow field and for validation of the CFD results.The analysis of the results has been focused on the flow structure in the diffuser,especially under part-load conditions.The detailed comparison between CFD and PIV results is performed.Vortical flow and recirculation flow patterns in the diffuser are captured and analyzed.Large flow separation and backflow appear under the part-load flow conditions.This paper provides a good data set for developing as well as evaluating the accuracy of various CFD models for capturing the complex flow field in a compact return diffuser used with multistage pumps.     

基于Fluent的亚音速翼型气动特性数值研究

根据Spalart-Allmaras模型建立了NACA0006翼型二维湍流流动模型,并对模型近壁面进行了网格加密处理.利用Fluent软件模拟了NACA0006翼型的二维湍流流动,得到在不同攻角及马赫数下升力系数和阻力系数的变化特性.研究结果表明,在所选攻角范围内,随着攻角的增大,升力系数和阻力系数均逐渐增大;在跨音速区,由于激波的产生,升力系数急剧下降.Fluent为研究翼型气动特性提供了重要参考和依据.     

非结构网格上双曲守恒律的并行算法研究

针对Euler方程的求解问题,在分布式存储环境下,提出一种适合于非结构网格上的并行算法。采用区域分解算法,适当处理网格,使每台处理器保持负载平衡。采用GMRES隐式时间离散格式、当地时间步长等加速收敛方法,通过对绕NACA0012翼型、ONERA M6机翼以及DLR-F6翼身组合体无黏流动数值模拟,验证了该方法具有较高的加速比和并行效率,适合在MIMD模式下进行大粒度科学计算。     

Analogy Theory and Application of Pressure Difference of Wind Turbine Blade Profile

风力发电叶片翼型型线理论及应用

张照煌,Aqeel Muhammad,张峻,刘青,李魏魏,宋玉旺

（华北电力大学 能源动力与机械工程学院 ,北京 102206）

中文说明：

经研究发现,在流动空气与风电叶片相互作用规律的过程中,真空中自由下落的空气团的形态与前后压差作用下流动的空气（风）非常相似;因此,本文提出以重量比拟压差设计风电叶片翼型型线的理论,即：空气团流过风电叶片翼型线的时间最短及应有尽可能多的空气团作用于该翼型线;以此为基础,本文推导出风电叶片翼型型线方程并进行了应用研究;通过从现有翼型库中选取三种相似翼型进行模拟对比,结果表明用本文建立的风电叶片翼型线方程设计的翼型线翼型(“SJX翼型”)在攻角变化时的升力及升力系数较所选取的三种翼型有较大的提升,翼型生阻比亦有小幅提升,且流动空气作用在气动中心的力矩均较大,验证了论文建立的风电叶片翼型线方程设计翼型型线的可行性和有效性,从而为风电叶片翼型型线设计理论的发展提供了新尝试和有益借鉴。

关键词：风力发电叶片;重量比拟压差;翼型型线;生阻比;翼型设计

     

采用粒子群算法的水平轴潮流能水轮机翼型多目标优化

为了提高水平轴潮流能水轮机叶片翼型空化性能,提出一种基于粒子群算法（PSO）的翼型性能多目标优化方法,主要针对较大攻角下翼型表面压力系数最小值;同时为保证翼型水动力性能,以翼型压力系数最小值及升力系数等建立多目标优化函数.通过程序调用XFoil对优化翼型水动力性能进行过程分析,替代计算流体动力学（CFD）分析,节省优化时间.采用此方法对NACA63-815翼型进行优化并采用CFD方法重点研究2个攻角工况下优化翼型与原翼型在3个空化数（1.0、1.5和2.0）下的空泡分布对比.结果表明,优化翼型在6.8°和10.8°攻角下压力系数最小值分别提升了17.0%和45.8%,最大升阻比提高了6.0%和61.1%.翼型的空化初生及全空化性能均得到明显提升,水动力性能也得到了提升,验证了此优化方法的可行性.     

超临界机翼静气动弹性特性研究

采用三维Euler方程为控制方程，计算机翼所受的气动力与静气动弹性平衡方程耦合求解，研究超临界机翼的静气动弹性规律，并以超临界弹性机翼和普通弹性机翼为算例，计算弹性飞机飞行中的真实载荷和扭转变形，并在已知弹性机翼飞行时总载荷保持不变的情况下，确定超临界机翼结构弹性在飞行中对载荷的影响。     

基于变形网格技术的翼型结冰数值模拟研究

翼型结冰的过程实质上是其外形随时间改变的过程。对于结冰的数值模拟,计算网格必须随着翼型外形的改变而相应的变化。文章利用非定常N-S方程模拟翼型结冰增长的过程,使用基于无限插值法(TFI)的变形网格技术生成非定常计算的网格。变形网格技术是在初始网格的基础上将物面的变化通过插值均匀分布到场内网格点,该方法能够最大限度地保留初始网格特征,而且生成过程与初始网格不相关。非定常计算利用上一次结冰的流场为初值,而不用从初场重新开始,而且变形网格技术生成网格也远远比求解椭圆型方程快,总的计算时间大幅减少。为了验证方法的有效性,文章对NACA0012进行了结冰数值模拟,计算结果与参考文献的实验和计算结果吻合。     

基于仿鸽子翼型的风力机叶片结构气动性能分析

对风力机轻风启动,有效利用风能进行研究。利用仿生耦合技术通过对鸽子翼型数据提取,建立仿生模型。基于NACA0015翼型及鸽子数据特征,将优缘凸起、后缘凸起及前后缘凸起三类翼型与NACA0015翼型进行对比,分析得到翼型上下表面压力分布、表面流场变化、剪切应力分布及增升减阻各气动系数,当失速攻角为16°、马赫数为0.073条件下,仿生翼型在提高升力方面比NACA0015提高了31.98%、降低阻力达到了10.62%,仿生翼型对表面流体起到了有效改善,改变结构的翼型对提高升力,降低阻力有了很大的提高。     

合成射流物理参数对控制翼型流动分离的影响

应用计算流体力学(CFD)技术数值模拟了合成射流对NACA0015翼型流动控制的影响.合成射流施加的位置分别距离翼型前缘12%c、30%c和70%c（c为翼型的弦长）,研究分析在不同位置施加合成射流,控制流动分离的效果随攻角和射流偏角的变化趋势,对组合射流的位置、相位角和动量系数进行研究.以二维不可压非定常Reynolds-averaged Navier-Stokes（RANS）方程模拟非定常分离流动,采用SST湍流模型,压力修正采用压力隐式算子分裂（PISO）算法,时间积分采用隐式处理方法,空间离散采用二阶迎风格式.通过对数值模拟结果的分析表明：1）12%c、30%c和70%c等对应的射流情形,采用切向射流均优于法向射流的控制效果; 2）对于组合射流和单一射流,射流位置应靠近分离点或在分离点之前,才能达到流动控制的目的,射流位置越靠近分离点流动控制效果越佳;3）组合射流选择合适的相位角,可以增强流动控制的效果.     

一种新型的垂直轴风力机聚风装置

为了提高垂直轴风力机的功率系数,设计一种能将任意方向的自然水平风转变成沿环形顺时针流动的风的环形聚风装置。分析了该装置将自然风转变为环形流时风的流场。计算有效进风面积,推导了半圆柱形叶片风轮和对称翼型的功率系数公式。研究表明,在不计装置对风的加速作用和忽略轮毂半径的情况下,半圆柱形叶片风轮功率系数最大值35.6%;在给定条件下对称翼型NACA0012的功率系数最高为41.5%;装置用于H型风力机,使得风力机具有确定的攻角及良好的启动性能。