尾部特征参数对气动阻力交互影响与全局优化研究

汽车尾部结构气动减阻优化时,各几何特征参数间往往存在此消彼长的现象,使得优化变得盲目而复杂.对此,为探明关键几何参数的交互影响规律,以Ahmed类车体为研究对象,在HD-2风洞试验对标验证基础上,对后背3个主要特征参数进行了CFD仿真研究,并在此基础上,为克服盲目性,应用集成优化平台对尾部特征参数进行优化设计.结果表明,后背倾角角度对减阻的贡献量最大,背部两侧圆角半径次之,后背顶部圆角半径最小;三者的改变对气动阻力的影响都具有非单调性;当后背倾角角度、后背顶部圆角半径和背部两侧圆角半径分别为13°、283 mm、58 mm时,能有效减小气动阻力,减阻率达到11.76%,为具体车型减阻优化研究提供借鉴.     

基于车轮的整车气动减阻的研究

针对国内某运动型多用途汽车(SUV),采用均匀设计方法,应用计算流体力学(CFD)技术,进行了车轮气动减阻研究.研究发现:使用均匀设计方法基于车轮的气动减阻能够有效地降低整车气动阻力系数,降幅可达15.9%,;前轮阻流板宽度对于针对车轮气动减阻的气动阻力系数的影响最大,前轮、后轮阻流板高度、宽度,轮辋面积对气动阻力系数存在不同的影响趋势.     

定常射流阵列控制地面车辆气动阻力

为了控制地面车辆气动阻力,通过风洞实验和大涡模拟仿真方法,研究定常射流对地面车辆流动控制的影响;研制由17只定常射流器构成的射流阵列装置,将其安装在车辆顶部和斜背交界处,进行流动控制实验;探讨射流倾角和动量系数等射流参数对三维地面车辆的非定常流动和气动力的控制机理。研究结果表明:数值仿真方法可有效模拟气动力变化趋势。动量系数不改变气动力变化趋势,仅影响变化幅值。射流倾角决定射流出口附近的速度分布,影响气流分离,导致气动力的差异。与无控制下相比,当射流倾角为-25°~65°时,可实现减阻;而当射流倾角为80°~115°时,对应的阻力未减小。     

仿生射流表面优化设计与减阻机理分析

针对不同射流表面参数减阻问题,建立仿生射流表面模型,利用SST k-ω湍流模型对其进行数值模拟,所得结果与实验数据吻合良好。运用正交试验设计法对影响射流表面摩擦阻力的因素进行分析,得到各因素对减阻效果和节能效果的影响规律:形状因子对减阻率和节能率的影响最大,流速比其次,流速比与减阻率和节能率呈抛物线关系,形状因子与减阻率呈线性关系,且随着形状因子增大减阻率增大,最大减阻率为15.06%,最大节能率为13.57%。由于射流流体的阻碍作用,在射流孔背流面形成逆流区,逆流区近壁面形成的剪应力方向与来流方向相反,局部摩擦因数为负值,并且由于射流流体对主流场的推力作用,使得边界层黏性底层厚度增大,速度梯度减小,摩擦阻力减小。     

25°Ahmed模型射流主动控制气动减阻策略

采用剪切应力输送(SST)κ-ω(湍动能-比耗散率)湍流模型对标准25°Ahmed模型进行基于计算流体力学(CFD)数值模拟的稳态射流减阻研究.在模型尾部设置射流孔,分别探究各位置处射流孔的孔径、到边线的距离、形状、射流速度和角度的最佳值,分析不同射流状态对流场结构、总阻力系数及局部阻力系数的影响.仿真的基本工况与风洞实验数据一致性很好,验证所采用数值方法的准确性和可靠性.研究结果表明,与未设置射流孔的模型相比,设置射流方案的模型尾流结构得以改善,纵向涡得以抑制,同时其阻力系数明显降低.单独位置布置射流孔方案中在斜面上方进行射流时,阻力系数最低,为0.252 2,减阻率为11.3%.通过正交试验获得最佳组合方案得到阻力系数0.246 7,减阻率达13.23%.     

基于等离子体流动控制的车辆减阻试验研究

在25°Ahmed汽车模型尾部斜面上端布置介质阻挡放电(DBD)等离子体激励器,通过风洞试验,研究了激励器频率为9 k Hz时不同激励电压对模型气动阻力系数的影响、10～25 m/s风速下的最大减阻率和此时对应的最佳激励电压. PIV测得的流场图以及PSI压力扫描系统测得的模型尾部斜面的压力值显示,在DBD开启时,激励器周围及尾部斜面近壁面区域流速提高,尾部分离区减小,尾部斜面上测压点处的压力升高;根据天平传感器测量结果,试验风速为15 m/s时获得最大减阻率,为7. 28%,对应的最佳激励电压为18. 5 k V. DBD激励器通过降低模型的压差阻力起到减阻效果.随着激励电压的提高,气动阻力系数呈现先下降后趋于平稳的趋势,且存在一个最佳激励电压;随着风速的增加,需要更高的激励强度才能起到较好的减阻效果.     

柔性飘带长度对Ahmed模型气动阻力的影响

为降低汽车行驶过程中的气动阻力,以尾部倾角为25°的Ahmed类车体模型为研究对象,提出在其尾部垂直面下边缘添加不同长度柔性飘带的控制方法,采用格子玻尔兹曼方法与有限元分析相结合的流固耦合计算方法,探讨了柔性飘带长度对汽车气动阻力的影响。首先对汽车模型进行格子尺度优化,得到模型的空气阻力系数;然后研究了柔性飘带对汽车气动阻力的影响;最后对模型尾部流场、柔性飘带附近流场以及模型尾部表面压力系数进行了分析。仿真结果表明：在模型尾部添加适当长度的柔性飘带,改善了尾流结构,提升了尾部表面压力,减小了车体的压差阻力,减阻率最高为12.25%。     

定常喷/吸流动主动控制方法减阻研究

针对Ahmed类车体,在车身斜面选定位置处设置控制槽,采用证明为有效的大涡模拟数值方法,研究喷/吸流动主动控制方法的气动减阻机理及效果.基于流场数据分析发现喷射控制致使车体斜面上流动大分离发生,拖曳涡对得以消除,但尾迹区尺度增大,气动阻力上升;抽吸控制方法抑制和消除展向涡结构的产生及发展,但拖曳涡对未受显著影响,气动阻力下降.     

基于等离子体的GTS模型气动减阻研究

为探究等离子体对类厢式货车的气动减阻效果,以GTS模型为研究对象,采用数值仿真的方法,分别研究了当来流风速为20 m/s时,3个位置处等离子体布置角度、激励电压对GTS模型的气动减阻效果并分析其减阻机理,然后进行组合工况的分析.研究结果表明,等离子体是通过诱导近壁面气体定向流动使流动分离点后移、推迟流动的分离,从而减小GTS模型前后压差阻力、降低整车气动阻力系数,等离子体布置的位置在流动分离点后方并且靠近流动分离点.单个位置激励时,等离子体布置在GTS尾部两侧时气动减阻效果最好,最大减阻率为5.09%;组合工况时最大减阻率可达6.01%.当来流风速一定时,等离子体存在最佳布置角度与激励电压.     

环量控制对翼型气动特性的作用机理

环量控制能够显著提高升力,改善飞行器短距起降性能。首先从机理上分析了环量控制的作用原理,然后通过CFD数值仿真方法研究环量控制对翼型气动特性的影响规律,采用雷诺平均N-S方程,SST湍流模型,将射流口边界条件设为反映动量系数的速度入口,分别模拟了动量系数和迎角对升阻特性和附面层分离特性的影响规律。结果表明:在α=0°,Cμ=0.05时,升力增加327%,效费比ΔCy/ΔCμ为21.97;随着动量系数增加,前缘分离导致失速迎角提前,在中等动量系数和小迎角状态能够获得优良的升阻特性。     

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.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

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.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

橡胶颗粒沥青混合料低温抗裂性试验研究

以AC-13级配为基础,将橡胶颗粒代替部分集料掺入混合料中,以低温弯曲试验为评价方法对不同橡胶颗粒掺量下沥青混合料的低温抗裂性进行研究,并引入应变能密度值对混合料的低温抗裂性进行综合评价.试验结果表明:橡胶颗粒沥青混合料试件的破坏微应变均超过2 300,满足冬寒区的技术指标;无论是否掺加橡胶颗粒,随着温度的下降,沥青混合料破坏时的最大弯拉强度增大,弯拉应变降低,劲度模量增大;弯曲应变能密度在胶粒掺量为1%左右时具有较大的弯曲应变能密度值,此时橡胶颗粒沥青混合料具有较好的低温抗裂性.     

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。     

Quantitative trait loci （QTLs） for quality traits related to protein and starch in wheat

Quality traits in wheat （Triticum aestirum L.） were studied by quantitative trait locus （QTL） analysis in a recombinant inbred line （RIL） population, a set of 131 lines derived from Chuan 35050 × Shannong 483 cross （ChSh）. Grains from RILs were assayed for 21 quality traits related to protein and starch. A total of 35 putative QTLs for 19 traits with a single QTL explaining 7.99-40.52% of phenotypic variations were detected on 10 chromosomes, 1D, 2A, 2D, 3B, 3D, 5A, 6A, 6B, 6D, and 7B. The additive effects of 30 QTLs were positive, contributed by Chuan 35050, the remaining 5 QTLs were negative with the additive effect contributed by Shannong 483. For protein traits, 15 QTLs were obtained and most of them were located on chromosomes 1 D, 3B and 6D, while 20 QTLs for starch traits were detected and most of them were located on chromosomes 3D, 6B and 7B. Only 7 QTLs for protein and starch traits were co-located in three regions on chromosomes 1D, 2A and 2D. These protein and starch trait QTLs showed a distinct distribution pattern in certain regions and chromosomes. Twenty-two QTLs were clustered in 6 regions of 5 chromosomes. Two QTL clusters for protein traits were located on chromosomes 1D and 3B, respectively, three clusters for starch traits on chromosomes 3D, 6B and 7B, and one cluster including protein and starch traits on chromosome 1D.     

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.