共查询到20条相似文献，搜索用时 968 毫秒
1.
Scaling properties of Navier-Stokes turbulence 总被引：1，自引：0，他引：1
Zhao-cun Liu 《浙江大学学报(A卷英文版)》2009,10(3):392-397
2.
Computational fluid dynamics (CFD) simulations were carried out on the gas flow patterns of twintangential annular deflector gas distributor in the absence of liquid flow in a packed column (6.4 m in diameter) , and the gas flow field in the column was presented close to reality on the whole. Furthermore, after amelioration of this gas distributor frame, turbulence energy and turbulence energy dissipation rate were both decreased greatly. Simulation results showed that the flow pattern and the distribution of gas flow were strongly affected by the column bottom frame ; the proper column bottom frame could decrease the flow pressure drop greatly. Multifold factors, such as the column bottom geometry structure and distributor structure which affects the distribution capacity, must be considered. 相似文献
3.
In the present study, considering the transport and transformation processes of variables, a threedimensional water quality model for the river system was established, which coupled the volume of fluid(VOF) method with the k-ε turbulence mathematical model. Then, the water hydrodynamic characteristics and transport processes for BOD_5, NH_(3~-)N and TP were analyzed. The results showed that the water surface of convex bank was a little lower than that of concave bank due to the centrifugal force near the bend, and most concentrations were inferior to the type Ⅴ standard indexes of surface water environmental quality. The model validation indicated that the errors between the simulated and monitored values were comparatively small, satisfying the application demands and providing scientific basis and decision support for the restoration and protection of water quality. 相似文献
4.
《福建教育学院学报》2014,(1):128-128
On the Identification of College and University Students withFinancial Difficulties
LIAO Shen-ji LINZi-hong LI Yan-li （Fujian Normal University, Fuzhou 350117, China）
Abstract： The scientific identification of college and universitiy students with financial difficulties is the precondition and foundation for providing them with proper subsidies. This study points out that the present problems existing in the process of identifying those college and universitiy students with financial difficulties include the comparatively simple method of identification, the unscientific criteria for identification, the nonstandard procedures of identification, and the inadequate supervision during the identification process. And it also puts forward some strategies for further improving the identification system of college and universitiy students with financial difficulties. Key words： college and universitiy; students with financial difficulties; identification 相似文献
LIAO Shen-ji LINZi-hong LI Yan-li （Fujian Normal University, Fuzhou 350117, China）
Abstract： The scientific identification of college and universitiy students with financial difficulties is the precondition and foundation for providing them with proper subsidies. This study points out that the present problems existing in the process of identifying those college and universitiy students with financial difficulties include the comparatively simple method of identification, the unscientific criteria for identification, the nonstandard procedures of identification, and the inadequate supervision during the identification process. And it also puts forward some strategies for further improving the identification system of college and universitiy students with financial difficulties. Key words： college and universitiy; students with financial difficulties; identification 相似文献
5.
Characteristics of strong winds at the Runyang Suspension Bridge based on field tests from 2005 to 2008 总被引：1，自引：0，他引：1
Field measurement of strong wind characteristics is of great significance for the development of bridge wind engineering. Located in east China, the Runyang Suspension Bridge （RSB） with a main span of 1490 m is the longest bridge in China and the third longest in the world. During the last four years, the RSB has suffered from typhoons and strong northern winds on more than ten occasions. To determine the strong wind characteristics of the RSB, wind measurement data obtained from field tests during strong winds and data from the wind environment monitoring subsystem of the structural health monitoring system （SHMS） of the RSB were combined to analyze the wind speed and direction, variation in wind speed with height, turbulence intensity, turbulence integral length, wind friction speed and the power spectrum. Comparative studies on the characteristics of these different strong winds were carried out based on the current wind-resistant design specification for highway bridges. Results showed that some regularity in wind characteristics can be found in these different typhoons passing through the RSB. The difference between a strong northern wind and a typhoon is relatively clear, and in summer the typhoon is the dominant wind load acting on the RSB. In addition, there were some differences between the measured strong wind characteristics and the values suggested by the specification, especially in respect to turbulence intensity and turbulence integral length. Results provide measurement data for establishing a strong wind characteristic database for the RSB and for determining the strong wind characteristic parameter values of this coastal area in east China. 相似文献
6.
Flow visualization and hot-wire measurement techniques were combined to investigate the influence of the size and number of tabs on jet flow field and vortex structure generation mechanism. Streamwise vortices generated by the tabs of different sizes and numbers were ob- served from the flow visualization images. Combined with flow visualization, hot-wire measurement gave a quantitative insight of the effect of various tabbed jet flows. Instantaneous two-component velocity signals （longitudinal and transverse velocity components） at different cross sections along radius direction and streamwise direction with different tabbed jet nozzles were measured using hot-wire anemometer. Average flow field parameters of tabbed jet flow such as mean velocity, turbulence intensity, vorticity were analyzed and the effects of tabs with different sizes and numbers were compared with that of circular no-tab jet flow. It is revealed that the generation of a series of counter-rotating quasi-streamwise vortices, azimuthal vortices and double-row azi-muthal vortex are the reasons for mixing enhancement of tabbed turbulent jet flow. 相似文献
7.
Mechanism of Breakdown in Laminar-Turbulent Transition of Incompressible Boundary Layer on a Flat Plate 总被引：2，自引：0，他引：2
Temporal mode direct numerical simulation was done for the process of laminar-turbulent transition in an incompressible boundary layer on a flat plate. The analysis of the results showed that during the breakdown process of laminar-turbulent transition, the modification of the mean flow profile by the disturbances led to a remarkable change in its stability characteristics, manifested in the significant enlargement of the linear unstable zone and the maximum amplification rate, and led to that many more disturbances were excited and enhanced rapidly, correspondingly the turbulent energy also increased rapidly, and the mean flow profiles evolved swiftly from laminar to turbulent. It was also found that if the oblique waves in the initial disturbances did not form symmetrical pairs, the subsequent span-wise mean velocities would, in general, be nonzero due to nonlinear interaction, which would have a great effect on the stability characteristics and also implied that the turbulence obtained by direct numerical simulation might not be fully a random process. 相似文献
8.
In this paper the modern electron-optical equipment is used to translate the clear image of speed-moving bubbles in bubbling liquid on a sieve tray into the digital information stored in computer,and the computeraided image-processing technique is utillized to measure the bubble size distributions and interfacial areas under various operating condtions.And the dynamic behavior of bubbles in trubulent liquid is analyzed theoretically; the mechnaism of bubble deformation and breakage is explored on the basis of Kolmogorff‘s isotropic turbulence hypothesis;the mathematical model for predicting the gas-liquid interfacial area is proposed ,The comparison between the simulated results and the experimental data show that the model is higher in accuracy ,simple in form and convenient in use. 相似文献
9.
The characteristics of acoustic emission(AE)signals given off in the course of the failure of a concrete structure is explored based on the laboratory experiments with concrete specimens.It is observed that the failure of a concrete structure experiences three stages divided by two inflexion points on the AE event curve,which are sequentially no damage,damage initiation and propagation,and major failure stages.In the first stage,existing micro cracks and defects are compacted by loading. but no damage propagated,hence few AE signals are detected,and it appears that there exists a nearly linear relationship between the relative stress and relative strain.In the second stage,the AE event frequency increases implying that micro cracks begin to emerge inside the concrete structure,which is consistent with the damage mechanics.When the load is over 80% of that breaks the structure,i.e.the maximum load,there is a vertical jump on the AE event count curve,which suggests that the failure propagation speeds up.After the second inflexion point,the AE event density increases faster than before,and there is another jump just before breaking,which indicates a quick propagation stage.These findings are valuable for evaluating the damage situations,and for studying and monitoring the dynamic process of the failure behaviors of a concrete structure. 相似文献
10.
The shelf life of pure amorphous sucrose systems, such as cotton candy, can be very short. Previous studies have shown that amorphous sucrose systems held above the glass transition temperature will collapse and crystallize. One study, however, showed that adding a small percent of another type of sugar, such as trehalose, to sucrose can extend the shelf life of the amorphous system by slowing crystallization. This study explores the hypothesis that raffinose increases the stability of an amorphous sucrose system. Cotton candy at 5 wt% raffinose and 95 wt% sucrose was made and stored at room temperature and three different relative humidities （%RH） 11%RH, 33%RH, and 43%RH. XRD patterns, and glass transition temperatures were obtained to determine the stability as a function of%RH. The data collected showed that raffinose slows sucrose crystallization in a low moisture amorphous state above the glass transition temperature and therefore improves the stability of amorphous sucrose systems. 相似文献
11.
武浩浩 《荆门职业技术学院学报》2011,(5):18-21
针对NACA4412翼型风力发电机扰流流动特点,建立了二维和三维不可压缩湍流模型,并对基于流体连续性方程和N-S方程及k-ε湍流模型的二维流场进行数值模拟计算。采用多参考系计算（MRF）模型,用FLUENT模拟了流场内翼型截面的受力情况和速度分布情况,得到了NACA4412翼型风机的气动特性。 相似文献
12.
针对变化风场尤其是大气紊流严重影响无人机飞行安全的问题,通过构建大气紊流数学模型并分析其对飞行的影响,为非线性无人机建立了六自由度模型,设计了一种模糊自整定PID控制器并进行了Matlab仿真。仿真结果表明,该控制器可提高无人机在变化风场中的稳定性和稳态精度。 相似文献
13.
在非标准扩大模型下,讨论了模糊拓扑空间中Q-紧集的非标准刻画．首先,将模糊集合扩张为非标准模糊集合,借助模糊点的重域定义了模糊点的单子．其次,以模糊点的单子为工具,给出了Q-紧集的非标准刻画,并在此基础上得到了Q-紧空间的非标准刻画．最后,证明了Q-紧空间的Tychonoff乘积定理． 相似文献
14.
在非标准模型下,讨论了集合标准部分的闭性.首先给出了非标准扩大模型和饱和模型这两大重要模型,以及拓扑空间中集合τ-邻域系的定义及有关命题.在此基础上给出了集合τ-单子和集合τ-标准部分的定义以及相关结论.最后证明了在非标准扩大模型和饱和模型下集合τ-标准部分是闭集的充分条件. 相似文献
15.
尹小帆 《泰州职业技术学院学报》2004,4(5):51-54
各类不规范的票据管理成为社会的一大问题，不规范的票据入账给企业管理和国家对票据的控制带来了很大难度，致使票据市场混乱，挥霍公款，偷税漏税现象严重。解决这些问题，一是加强内部控制，建立内部电算化管理体系，费用报销的薪酬制，内部员工监督机制。二是强化外部监督机制，统一票据管理数据化，控制费用列支环节，加大检查力度及对造假处罚力度。 相似文献
16.
论俗字 总被引：1，自引：0，他引：1
石云孙 《安庆师范学院学报(社会科学版)》2000,(1)
俗字是世俗所行之字。古字少 ,后世大众出于记录、表达需要造了大量的俗字 ,是中华汉字的新生代。历代相承 ,蔚为大观。因字书收录 ,保存了汉字资源。俗字不俗 ,通俗而不浅陋 ,利在便俗 ,亦难违俗。对俗字应宽容 ,少非难 相似文献
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为天津地铁改建、扩建所需 ,采用数学模拟方法对原有站台通风系统的气流组织效果进行评价 ,在此基础上提出通风系统的改建方案 ,并对新方案的速度场、温度场进行优化 .借助实际流场的测试数据判断紊流模型的适用性 ,并通过现场测试获得了所需边界条件值 .模拟结果与实测数据相符 ,证明了双方程紊流模型用于模拟站台的复杂流场是可行的 .模拟时将列车进站过程的瞬时流简化为稳定流 ,并对此假设前提下模拟结果的有效性给予认证 . 相似文献
20.
颜景和 《扬州职业大学学报》2012,16(4):20-22
针对某气体流量非标准节流装置测量方案,提出一种非标准节流装置特性参数间接检测方法,实现了一种非标准孔板气体流量的测量,并使该方案产品化。提出的非标节流装置特性参数间接检测方法易于工程实现,具有较好的实用价值。 相似文献