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1.
搭建了整备状态下的某高速列车动力车厢有限元模型,包括白车身、内饰件和牵引传动系统.提出了多物理场激励耦合作用下的高速列车车内结构辐射噪声分析方案,分别采用刚性多体动力学、边界元法和大涡模拟获取了二系悬挂力、轨道噪声和车体表面压力脉动,与车体模态耦合后得到车体结构的振动响应.完成了时速350,km/h下的列车搭载试验和车体结构响应计算,在地板上随机选取了一个振动测点,仿真与试验得到的振动速度级曲线趋势和幅值具有较高的一致性,验证了仿真模型与多物理场耦合激励的精度.最后采用耦合边界元分析了耦合激励下的车内结构辐射噪声.  相似文献   

2.
汽车前侧窗表面的压力激励是前侧窗区域非定常流动和气动噪声的重要体现指标.这一区域复杂的非定常流动产生更大尺度范围的涡结构,从而导致前侧窗表面复杂的非定常压力激励.本文通过基于声学扰动量方程组(APE)的混合计算气动声学(CAA)方法分别获得汽车前侧窗表面的湍流压力激励和声学压力激励.引入动力学模态分解(DMD)对前侧窗表面的压力激励进行分析,指出湍流压力激励基于频率的区域分布特征和声学压力激励辐射声场特征.讨论了湍流压力激励、声学压力激励以及不同的激励源对车内噪声的相对贡献量. DMD识别的前侧窗表面主要的湍流压力激励是由后视镜尾迹的脱落涡产生的,其特征频率为59 Hz,与试验测量结果一致,验证了湍流压力激励计算结果的有效性.通过对比前侧窗区域空间截面上相同频率的湍流压力和声学压力的DMD模态,识别出前侧窗区域主要的声源位置,一个位于后视镜基座处,由这一区域的后视镜基座涡的涡对流产生.另一个位于后视镜镜体的下缘,由这一区域的分离涡产生.后者由风洞试验中的传声器阵列识别出来,验证了声学场计算结果的有效性.  相似文献   

3.
为有效控制水下复合材料结构受湍流壁面脉动压力激励引起的结构自噪声,利用模态展开技术和高阶剪切形变理论,结合湍流壁面脉动压力功率谱建立了水下湍流壁面脉动压力激励复合材料板的Rayleigh-Ritz模型,并推导了结构振声响应的封闭解.利用该方法探讨了复合材料板的弹性模量、密度、阻尼等材料参数,以及铺层角度和厚度等参量对水下湍流激励引起结构振动和声辐射的影响.研究发现:通过增大结构阻尼是抑制水下湍流壁面脉动压力激励复合材料板的振声响应的最佳有效途径,同时提高结构抗弯刚度也能达到较好的减振降噪效果,尤其在抑制振动方面作用显著.  相似文献   

4.
汽车外部流场和脉动压力模拟计算   总被引:1,自引:0,他引:1  
为了解车辆在高速行驶时产生的气流噪声的规律,分析了产生气流噪声的机理,采用大涡模拟方法计算了某轿车模型的瞬态外流场和表面脉动压力,得到了表面脉动压力频谱特性、速度特性和分布特点.计算结果表明,汽车A 立柱后气流明显折转,在侧窗处产生气流分离区,分离区的漩涡不断生成和脱落,在侧窗玻璃上产生了压力波动,即形成了声学噪声源--脉动压力.车辆表面脉动压力在低频区较大,并随频率的增加而减小,在高频区较小,约与风速的4次方成正比,即风速每增加1倍,脉动压力级增加12 dB左右,计算结果与试验结果基本一致.  相似文献   

5.
为分析高速列车车内低频噪声主要来源,利用振动声辐射理论研究了车内声场特性与内饰板振动的关系.实验室半实物试验结果表明,内饰板振动和车内声场耦合响应特性在空气声和结构声传播过程中具有普遍适用性.应用该方法对某高速列车不同速度级、明线和隧道运行条件下的车内噪声特性进行分析.结果表明,列车运行速度越高,内饰板低频振动幅值增加越显著,这导致车内低频噪声的峰值更加突出.对于350km·h~(-1)速度工况,明线工况的低频噪声峰值主要来源于地板结构声辐射,而隧道环境下的噪声增加主要来源于侧墙和车顶结构的声辐射,并对各面板贡献度进行了定量化计算.最后,用工况噪声传递路径分析(OTPA)方法开展了噪声源贡献度定量化计算,结果表明,气动噪声所占比重最大,但振动激励的总和达60%,尤其是160Hz的峰值频率处,风机振动激励的贡献度最大.  相似文献   

6.
基于随机理论,采用半解析半数值方法,以单双层圆柱壳模型为例,计算了湍流激励下单双层圆柱壳的输入功率谱密度和振动速度功率谱密度,对比分析了单双层圆柱壳的振动特性.结果表明:随着航速增高,湍流脉动压力激起壳体表面振动速度的自功率谱密度幅值变大,趋势基本相同;同一航速下,湍流脉动压力作为面分布力作用在壳体外表面上,由于双壳体的外壳较薄,因此双壳体振动速度响应大于单壳体的.  相似文献   

7.
多类振动噪声源下舰船水下噪声的耦合声场计算方法   总被引:1,自引:0,他引:1  
针对具有DTMB 5415船型的某护卫舰,提出水动力、机械和螺旋桨等3类典型振动噪声源共同作用下舰船低中频水下噪声的耦合声场计算方法.基于URANS方法采用SST k-ω湍流模型,数值模拟了该舰在某航速下的非定常流场,并将其作为该舰的水动力噪声源;以某型螺旋桨的脉动压力与实测噪声数据作为机械振动源和螺旋桨噪声源.建立了该舰结构有限元-流体声学间接边界元(FEM-IBEM)声振耦合计算模型,以船体结构前40 000阶干模态作为声振耦合求解声学响应的模态基,计算了该舰在上述3类噪声源共同作用下0~500 Hz水下辐射声功率级,分析了各类噪声源辐射噪声的指向特性和频谱特性.比较了工程中常用的各噪声源辐射声级直接线性叠加方法与耦合声场计算方法的差异.研究表明,耦合声场计算方法的计算效率和精度更高,是多类振动噪声源激励下舰船低中频水下辐射噪声预报的优选数值计算方法.  相似文献   

8.
针对高速列车的头车进行全尺寸三维模型和流场流域的创建,并通过k-ε湍流模型计算稳态流场;在稳态流场的基础上,采用宽频带噪声模型计算头车表面的气动噪声源;利用大涡模拟(LES)方法计算瞬态流场,进而获取车身外表面的脉动压力;再基于瞬态流场,采用Lighthill声类比理论研究头车远场气动噪声的计算.最后,比较气动噪声的仿真分析结果与实地试验结果,验证了仿真结果的正确性.  相似文献   

9.
为了研究加环肋轴对称壳的声振特性,建立了计算两端带半球帽圆柱壳水中声辐射的有限元与边界元三维模型,分析了加肋高度、宽度、数量对轴对称壳表面平均振动速度、辐射功率、辐射效率、激励点法向声强、声场指向性的影响.应用有限元软件Ansys建模及模态分析方法,将数据导入边界元软件Sysnoise中计算,从而分析结构耦合状态下的辐射声场特性.结果表明,随着环肋高度、宽度及数量的增大,激励点法向声强、表面平均振动速度以及辐射效率和辐射声功率随频率变化曲线的峰彼此错开;环肋高度、宽度、数量增大时激励点法向声强以及辐射声功率均有增加,表面平均振动速度减小,因而导致声辐射效率增加;在0~800Hz频率范围内,环肋高度和宽度变化对声场指向性影响差别较小.  相似文献   

10.
基于设计灵敏度分析的圆柱壳声辐射优化   总被引:2,自引:0,他引:2  
采用有限元法计算结构振动,边界元法求解结构振动引起的辐射声场问题.在此基础上提出了圆柱壳结构声辐射优化模型,重点推导了结构振动声辐射灵敏度计算公式.优化模型中,声辐射功率作为目标函数,约束函数中不仅有内部场点平均声压作为声场设计指标,而且包含了质量和自振频率的结构设计指标,圆柱壳的厚度作为设计变量.通过与用差分法计算的...  相似文献   

11.
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.  相似文献   

12.
何延凌 《科技信息》2008,(4):258-258
Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women's language from these perspectives: pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women's language, more attention should be paid to language use in social context. What's more, the linguistic phenomena in a speaking community can be understood more thoroughly.  相似文献   

13.
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.  相似文献   

14.
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。  相似文献   

15.
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.  相似文献   

16.
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.  相似文献   

17.
王慧 《科技信息》2008,(10):240-240
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.  相似文献   

18.
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.  相似文献   

19.
In the 19th century the society was controlled by men, and women were just appendants of them, they had not any rights and freedom. But Jane was an exception, she showed some characteristics of early feminist. Jane showed her characteristics of feminism in three aspects: rebellion, equality, and independence. These characteristics were helpful to her success, and feminism is the only way out for women of that time.  相似文献   

20.
AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…  相似文献   

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