查询词典 turbulent flow

The simulation results of the cylinder-block model were given in the article, consistent with that of Middlemen"s. It was shown that the block part could improve the uniformity of the flow distribution. The analysis of the flow field of some materials with different power-law factor in the die designed by Mckelvey was close to that of Mckelvey"s. It was shown that the flow distribution was uniform in the die that can producesheets with 1200mm in width. During the analysis the flow channel was divided into several parts to get the details about the fluid flow in each area. A conclusion was drawn after analyzing the influence of the die pressure on the flow distribution, that the higher pressure is good for the output and bad for the uniformity of the distribution. Simulation of the die applying the cylindrical main runner showed the fact that when the cylinder replaced the cone the change of uniformity was trivial. The uniformity of the non-block flow channel was so poor that the block in the proper position of the die channel was necessary. The project of the die for the wider sheet was put forth, and the analysis of the fluid flow in the die was shown.

本文模拟了圆柱管缝隙流模型的三维流动场，得到了与Middlemen结论一致的流动均匀性，并通过模拟直观地展示了采用阻尼块可以改善挤出均匀性的现象；分析了多种幂率指数的流体在Mckelvey等人设计的流道模型中的流动分布，得到了与Mckelvey的分析结果接近的压力降和流量偏差；本文建立了1200mm幅宽机头流道的三维有限元模型，并逐个分析各个区域和多个截面的流动分布状况，由此揭示了1200mm幅宽L-型机头流道内的流北京化工大学硕士学位论文动分布基本均匀，并在分析了机头压力对于挤出流动分布的影响后得出结论：较高的机头压力可以获得较大的产量，但是不利于物料均匀分布；模拟了采用圆柱管主流道时机头流道内的流动分布，得出结论：主流道由圆锥管改为圆柱管时对流动均匀性影响不大，通过设置适当的阻尼仍然可以达到挤出平衡；模拟了两端进料式圆柱管无阻尼流道的流动均匀性后得到结论：两端进料式无阻尼结构的流动均匀性较差，宽机头中仍然有必要设置阻尼块；确定宽幅机头流道的基本方案，并设计了一种宽幅防水卷材挤出机头流道的结构，通过流动模拟表明该种结构的流动均匀性较好；考察了宽幅机头对于不同厚度片材的挤出适应性，得到结论：当生产不同厚度的片材时，阻尼块高度需要调整。

Flow regime and void fraction are important parameter in gas-liquid two-phase flow, the relation of differential pressure signal coming from Venturi tube and the flow regime of gas-liquid two-phase flow was studied in this paper, A kind of flow regime identification method of gas-liquid two-phase flow based on Hilbert-Huang Transform and fuzzy inference was put forward, the familiar flow regime identification of gas-oil and gas-water two-phase flow was achieved.

两相流动是一个十分复杂的过程，参数较多，检测相当困难。流型、空隙率是气液两相流中非常重要的参数，而且测量比较困难，还影响两相流其它参数的测量。

A nonlinear eddy-viscosity turbulent flow model, which adopted third-order correlation of stress tensor and strain tensor, was modified and applied to flow computing of turbulent flow of internal combustion engine.

把采用了应力张量和应变张量的三阶相关关系的一个非线性涡粘度湍流模型进行修正后应用于内燃机缸内湍流流动计算，用此模型对几种ω形凹坑燃烧室内燃机汽缸内的流动进行计算，特别考查不同结构燃烧室内各处的湍能的变化，给出了燃烧室结构对缸内湍能影响结果，结果表明，凹坑结构时内燃机缸内湍能的分布和平均湍能的大小影响很大，可适当调整燃烧室结构来改变缸内湍流结构。

The mean velocity distributions in turbulent boundary layers of smooth surface and two different riblet surfaces are measured with IFA300 constant-temperature anemometer in low-speed wind tunnel to validate the full development of turbulent boundary laye. Friction velocity and wall friction stress of turbulent boundary layer are obtained with the least-squares fitted curve of the sublayer velocity distribution based on Spalding formula, and virtual origin position of riblet surface can be acquired accurately.

在低速风洞中来流速度一定的情况下使用IFA300恒温热线风速仪测量了光滑表面和两种不同尺寸的脊状表面湍流边界层平均速度分布剖面，并验证了试验段湍流发展的充分性；通过应用Spalding壁面公式使用最小二乘法精准拟合了实验测量的边界层内层速度分布曲线，得到了湍流边界层壁面摩擦速度并进一步求得湍流壁面摩擦应力，较准确地计算出脊状表面的虚拟原点位置，并通过与对数律公式拟合结果比较分析，证实了该方法更加准确有效。

Therelationship between the turbulent kinetic energy and its dissipation rate,whichis widely used to parameterize the dissipation rate in turbulence closure models,is found to hold well for both reversing and rotating flows,but with differentcoefficients.Microstructure profiling measurements at two comparative stations (a deepercentral basin and a local shelf break) in the stratified Yellow Sea are analyzed,with emphasis on tidal and internal-wave induced turbulence near the bottomand in the pyenocline.The water column has a distinct three-layer thermohaline structure,consisting of weakly stratified surface and bottom boundary layers anda narrow sharp pycnocline.Turbulence in the surface layer is controlled by thediurnal cycle of buoyancy flux and wind forcing at the sea surface.while thebottom stress induced by barotropic tidal eurrents dominates turbulence in thebottom boundary layer.The maximum level at which the tidally enhanced mixingcan affect generally depends on the magnitude of the tidal current,and it canbe up to 10-15 m in the Yellow Sea.This suggests that,in the deeper regionsof the shelf seas,turbulent dissipation and mixing are very weak at the levelsbetween the near-bottom tidally enhanced layer and the pycnocline.Therefore,these levels provide a significant bottle neck for the vertical exchanges.In theshallow regions,however,the tidally-induced turbulence can occupy the wholewater colum below the pycnocline.A quarter-diurnal periodicities of the turbulentdissipation rate and eddy diffusivity are found at different heights with evidenttime lag.In the relatively flat central basin,the pycnocline is essentially non-turbulent and internal-wave activity is very weak.Therefore,vertical fluxes acrossthe pycnocline decreased to molecular levels.In contrast,internal waves of variousperiods can be always found near the local shelf break.

对强层化季节黄海两对比性站位(分别位于中央海盆区与局地陆坡区)处层化、内波以及湍流混合特征的研究结果表明：1、强层化季节的陆架海水体一般呈现显著的三层热盐结构，在水体近乎混合均匀的上混合层与潮流底边界层之间为强跃层；2、近表层水体的湍流混合强度主要由海表浮力通量的日变化与海表风强迫控制，而在潮流底边界层内，潮混合是水体热量、物质、动量与能量垂直交换的主要机制；3、潮混合影响的深度由潮流大小决定，在黄海，一般可达10-15 m，因此，在水深较深的区域，在跃层与潮混合所至深度范围的上界之间存在湍流混合非常弱的区域，这显著抑制水体内物质的垂直通量，为物质垂直交换的瓶颈，而在水深较浅的区域，潮混合影响范围可至跃层底部，因此物质在跃层以下整个水体中混合非常均匀，当跃层内间歇性强混合发生时，可以产生显著的跨跃层物质输运；4、近底潮致强湍流耗散缓慢地向上传播，底上不同深度处垂直湍扩散系数也具有显著的位相差异，且二者均随时间呈现四分之一周日周期的变化；5、在地形较为平坦的中央海盆区，内波活动非常微弱，因此跃层内湍流混合非常弱，垂直扩散系数为分子扩散水平，跨跃层物质通量受到显著抑制，而在地形变化较为显著的局地陆坡区，内波活动非常活跃，除内潮的影响外，高频内波与内孤立波的影响也很显著，因此跃层内存在很强的间歇性强混合，内孤立波存在的区域，水体湍流混合显著增强。

Results of simulation indicate that a series of "second-vortex" are produced in the riblets structure, turbulent kinetic energy and turbulent burst intensities are debased, which reveals reasonably turbulent drag reduction mechanism.

数值仿真结果则发现，在脊状结构内形成了稳定的&二次涡&，边界层内湍动能和湍流猝发强度降低，很好地揭示了减阻机理。

Constant Flow Valve and the constant flow regulating valve are different: there is only one fixed flow valve valve from the valve directly feel before and after the differential pressure valve, the implementation of change in valve resistance action can be "direct action type variable resistance valve "It should not regulate the flow line, so the use of Constant Flow Valve can not be implemented to change the total flow of energy to run, and this set the flow valve as there are no imports of expensive, in the past, domestic heating systems seldom used, and only at some central air conditioning system to see.

定流量阀和恒流量调节阀不同的是：定流量阀只有一个阀瓣，由这个阀瓣直接感受阀门的前后差压，执行改变阀门阻力的动作，可成为"直动式变阻力阀"，它不能在线调节流量，因此使用定流量阀无法实施改变总流量的节能运行，而且这种定流量阀国内没有，进口的价格昂贵，以往国内的供暖系统很少采用，只有在一些中央空调系统中见到。

Constant Flow Valve and the constant flow regulating valve are different:there is only one fixed flow valve valve from the valve directly feel before and after the differential pressure valve,the implementation of change in valve resistance action can be"direct action type variable resistance valve",闸阀;It should not regulate the flow line,so the use of Constant Flow Valve can not be implemented to change the total flow of energy to run,and this set the flow valve as there are no imports of expensive,in the past,domestic heating systems seldom used,and only at some central air conditioning system to see.

订流量阀和恒流量调节阀不同的是：定流量阀只需一个阀瓣，由这个阀瓣直接感受阀门的后后佳压，执行转变阀门阻力的动做，否成为"直动式变阻力阀"，facebook外白板，它没有能在线调节流量，研建课，因己运用定淌量阀无法实施改变合流量的节能运行，而且这种定流量阀海外不，入口的价钱昂贵，以来国内的供暖体系很少采用，只需在一些中央空调系统内见到。

Correctional checking formula of melt flow ratio in injection molding was obtained by introducing a correction coefficient β which reflected the complexity degree of mold cavity. The results show that, the maximum flow ratio of 486 can be obtained when injection pressure ranges from 150 MPa to 160 MPa in Archimedes spiral mold for PP, while maximum flow ratio of 419 can be obtained when injection pressure ranges from 160 MPa to 170 MPa for PE. There is a local fluctuation phenomenon for flow ratio and corresponding injection rate in square spiral mold when injection pressure of 100, 120 and 150 MPa for PP and 130, 140 MPa for PE are reached respectively,and this phenomenon is more serious for good fluidity of melt. The average flow ratio in Archimedes spiral mold is 6% larger than that in square spiral mold for PP, and 4% for PE, the average flow ratio of PP is 19% bigger than PE in Archimedes spiral mold, and 15% in square spiral mold. The influence of the cavity profiles on the melt flow ratio is more significant for good fluidity of melt.

研究结果表明：在阿基米德螺旋线模具中，PP在注射压力为150~160 MPa时取得最大流动比485，PE在注射压力为160~170 MPa时取得最大流动比419；在方形螺旋线模具中，PP在注射压力为100，120和150 MPa，PE在注射压力为130和140 MPa时流动比及所对应的注射速率出现波动，且流动性好的熔体波动更为严重；PP在阿基米德螺旋线模具中的流动比均值较其在方形螺旋线模具中大6%，而PE大4%；在阿基米德螺旋线模具中流动比均值PP比PE的流动比均值大19%，而在方形螺旋线模具中PP的流动比均值比PE的大15%；流动性好的熔体受模具型腔轮廓特征影响大。

The stratified flow, slug flow and asymmetry annular flow upstream become symmetry annular flow with uniform film thickness after the spin generating element. The liquid extraction ratio is only determined by the diameter and number of the sampling holes and independent of gas and liquid flow rate of the main pipe, and the gas extraction ratio is mainly controlled by the liquid flow rate of the main flow loop.

分析表明，取样流体中的液相质量流量与主流体液相质量流量的比值主要取决于取样孔的数目和大小，而取样流体中的气相质量流量与主流体气相质量流量的比值则与主管路液相流量有关。

She said that it would be a cold day in hell before she befriended the former jailbird.

她表示要是和希尔顿这个蹲过监狱的人做朋友的话，简直就是和下地狱一样。

As usual, when his parents don't like what he wears, they start to bugging him.

像往常一样，当他的父母不喜欢他的穿着时，便开始唠叨他。