风力机叶片翼型气动特性数值模拟

为研究风力机转子叶片的翼型特征,通过Fluent软件对改进的NACA类风力机转子叶片翼型的绕流流动气动特性参数进行数值模拟分析.结果表明:对于改进的NACA类转子叶片,翼型特征的优化保留了叶片高升力,进一步降低了阻力,在多攻角范围内均获得了较好的升力系数和升阻比.当攻角较小时,叶片绕流流动即呈现较小的分离涡,随着攻角的上升,叶片正负压强差进一步增大,表面压力系数特征规律趋于稳定,尾部涡进一步扩大,表现出强烈的分离流动特性.翼型的优化设计可以直接提高风力机转子叶片的气动特征,进而提高风力机的工作性能.     

陆空平台旋翼叶型参数气动性能多目标优化研究

陆空平台兼具旋翼无人机和无人车的特点,对各种室内外复杂作业环境均有较佳的适应性,但不同作业环境对旋翼的升力、悬停效率等气动性能的需求并不一致,单一叶型难以满足这种差异化需求. 针对此问题,基于类函数/形函数方法,以伯恩斯坦多项式对翼型弦长、扭转角和旋翼前缘位置沿径向的分布进行了参数化表述,实现原旋翼叶型的三维参数建模重构,随后采用数值方法进行了关键叶型参数对气动性能的敏感性分析. 计算结果表明,翼尖附近的弦长和扭转角对气动性能影响较大,且弦长和扭转角间存在明显的交互效应. 据此以升力和品质因子为目标,对原旋翼叶型进行了多目标优化设计并进行了试验验证,试验结果表明,高升力叶型的旋翼升力系数提高了13.2%,高品质因子叶型的旋翼品质因子提高了37.8%,基于伯恩斯坦多项式与类函数/形函数方法结合的叶型三维参数化优化方法,能够有效提升旋翼升力或品质因子等气动性能指标.      

振荡射流控制翼型流动分离的数值模拟

为了研究大攻角下振荡射流控制翼型流动分离的机理,应用基于有限体积法和压力修正的SIMPLEC算法,数值模拟了表面施加振荡射流的翼型分离流动。结果表明振荡射流在给定条件下能够显著改善翼型的气动性能,提高翼型的升力系数,升力增幅高达18%。对振荡射流增升的流动机理分析表明,增升的机理是因为振荡射流产生的小扰动完全改变了翼型在大攻角粘性流动时产生的涡列结构,并且在翼型头部产生了非定常的分离涡。     

大攻角下开缝位置改变对风力机叶片影响研究

风力机叶片在大攻角条件下存在着严重的流动分离现象,降低风电机组的发电效率,文章采用计算流体力学方法研究开缝位置改变对风力机叶片性能的影响。研究结果表明:在一定攻角范围下,射流会改善流动状况,缩小涡旋结构影响区域;开缝位置位于分离点附近时,气动性能最好,随着射流位置后移,其控制效果减弱,即使射流位置位于回流区,仍可减弱回流区影响范围与强度;射流有利于提高叶片升力系数,改善大攻角下叶片气动性能及稳定性。     

升阻互补型垂直轴风力机气动性能分析

为了提高垂直轴风力机的风能转化率,提出了一种新型升阻互补型垂直轴风力机.对大厚度航空翼型进行切割得到了升阻型叶片翼型,基于CFD数值模拟技术,分析了改进后翼型以及利用该翼型制成的端部封闭和不封闭的两种垂直轴风力机的气动特性.计算结果表明,改进后的翼型具有较高的升力系数,但失速特性和阻力特性较差,两种垂直轴风力机在额定工况下均产生了较高的风能利用系数,而端部不封闭叶片由于叶梢部位产生湍动能较低,具有更好的动力输出,叶片在逆风运行时,充分发挥了翼型外表面的升力性能.     

Gurney襟翼对叶片流场影响的数值模拟

为了验证添加Gurney襟翼的一种风力机叶片在各种风速下的实际增升效果,用计算流体力学的方法计算NREL Phase VI风力机叶片以及加Gurney襟翼(3%的翼型弦长)后叶片的流场,比较不同来流风速下叶片表面的压强分布与流速分布.计算结果表明,加Gurney襟翼后叶片压力面的压力有所增加,吸力面压力降低,且各面压力分布趋于均匀,压力面和吸力面的压力差显著增大,提高了风力机叶片的升力.     

涡流发生器对垂直轴风力机翼型气动性能的影响

为推迟翼型的边界层分离,改善叶片的气动性能,提出一种在H型垂直轴风力机对称翼型NACA0012叶片表面上加装涡流发生器的设计方案。利用FLUENT软件对翼型进行三维流体力学仿真,采用正交试验设计法,研究涡流发生器的高度、安装角度和安装位置这3个设计参数对翼型气动性能的影响。研究结果表明:最佳的涡流发生器高度为6.5 mm、安装角度为18°、安装位置为0.1c(c为叶片弦长),过大或者过小的涡流发生器高度和安装角会降低翼型的升力系数和升阻比;安装位置靠近翼型前缘可增大翼型的临界攻角,但会给翼型带来较大阻力;加装涡流发生器后,对称翼型叶片失速区范围减小40.3%。     

多兆瓦级风力机叶片的优化设计与动力学特性分析

考虑实际气流流动过程中周向速度的变化情况,即采用Schmitz理论来设计2 MW风力机叶片的气动外形.将计算得到的叶片翼型参数进行坐标变换,获得各个截面上叶素的三维坐标,利用三维建模软件建立叶片的三维实体模型,并将其导入至有限元分析软件中,进行模态特性和气动弹性分析.讨论了不同铺层厚度和铺层角度对叶片模态特性和气动弹性的影响规律.仿真结果显示:在铺层厚度为0.6mm和铺层角为60°时,叶片具有较好的模态特性;叶片所受的气动集中载荷随着叶片弦长几乎成线性增长,且在弦长最大时集中载荷最大;当铺层角等于44°时,叶片在气动载荷作用下的最大集中应力最小,具有最佳的气动弹性特性.     

加装叶片涡流发生器对变桨距风力机功率的影响

以风力机专用厚翼型DU99-W-405LM为对象,采用CFD方法对洁净翼型段及安装涡流发生器后的翼型段进行数值模拟.研究结果表明:在一定攻角范围内涡流发生器可有效推迟流动分离,提高翼型升力,降低阻力,改善叶片气动性能,并揭示了涡流发生器控制流动分离的机理.通过甘肃西滩风场1.5 MW风机安装涡流发生器前后功率试验数据对比分析,表明在风速7～10 m/s风力机功率增量最大,最大值达到181.42 kW,比安装前功率提高了28.8%,试验数据表明安装涡流发生器改善叶片的气动特性是有效的,可以提高风力机机组发电功率.     

小型水平轴风机叶片实体建模研究

研究了小型水平轴风力机叶片的实体建模.首先,通过对比NACA4412和FX63-100两种翼型的气动性,选用更优的FX63-100翼型对风力机叶片进行外形建模设计,然后基于坐标变换原理,运用Excel软件得出翼型的数据,通过solidworks进行叶片的三维实体建模.沿叶片半径方向对翼型弦长和扭角进行三次多项式拟合修正,优化了风力机叶片外观且改善了其加工工艺,提高了生产效率并节约了成本.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

《Chinese Science Bulletin》SUBJECT INDEX TO VOLUME 59(2014)

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Achieving Unusual States of Matter Under High Pressure

The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to     

Exciton Seebeck in Molecular Systems

Various applications relevant to the exciton dynamics,such as the organic solar cell,the large-area organic light-emitting diodes and the thermoelectricity,are operating under temperature gradient.The potential abnormal behavior of the exicton dynamics driven by the temperature difference may affect the efficiency and performance of the corresponding devices.In the above situations,the exciton dynamics under temperature difference is mixed with