查询词典 turbulent

For the turbulent developing flow of absorbing and isotropic scattering medium in a circular tube, the steady state heat flux of the coupled heat transfer of turbulent convection and thermal radiation under constant wall heat flux was investigated numerically.

对圆管内物性随温度变化的吸收-各向同性散射介质的湍流入口段，数值研究了定热流加热下辐射与湍流正在发展流耦合换热的稳态热流特征。

The experimental setup for the turbulent jets in crossflow is designed, and the hot wire anemometry IFA 300 is used to measure the velocity field and the turbulent kinetic energy, and the computational result matches experimental measurement reasonably well. The experimental result is very important in the analysis of the flow field, deduction of the equation of the jet trajectory, check of the turbulence model and validation of the numerical method.

首先，建立了用于测量横向紊动射流的实验台，并利用IFA 300型热膜风速仪系统测量了多种工况下的流场，并将速度、湍动能结果与数值计算结果进行了比较，实验结果与数值模拟结果吻合较好，从而为分析流场特性、确定射流轨迹、比较湍流模型以及验证数值计算方法提供了依据。

Firstly, the two parts are solved separately, and the results are then coupled together. Because the thickness of the combustion reaction zone at high Re and Da numbers is less than the turbulent diffusion scale in diesel engines, the flame is extremely thin, its micro-structure keeps the laminar structure, so the turbulent flame can be regard as the ensemble of locally one dimensional, thin laminar flamelet embedded within the turbulent flow field.

由于柴油机中在高雷诺数和高Damkoeler数的情况下，燃烧反应区厚度小于湍流耗散尺度，火焰极薄，其微元保持层流结构，因此，湍流火焰可视为嵌入湍流流场内局部具有一维结构的薄的层流小火焰的系综，这便构成了层流小火焰模型主导思想，同时也使层流小火焰模型模拟柴油机湍流燃烧过程成为可能。

Main creative points of the thesis are as following:1. It is the first time to apply 2-D and 3-D turbulent model of the air-water two phases flow to the study on hydraulic properties of groyne. It makes description of the turbulent flow field to be possible precisely. This offers a more accurate method to determine the water surface in channel improvement.2. Based on the results of experiment and simulation for 3-D turbulent model of air-water two phases flow, a new formula to compute the height of damming is built.3. Based on the 2-D mode and the formula to compute the height of damming, the subdivision method of 2-D computation for water surface at upstream and downstream.

本文的创新工作主要是：首次将三维水气两相流紊流数学模型应用于丁坝水动力学特性研究，使丁坝附近流场和紊动场的精细描述成为可能，为航道整治中水面线确定提供了一个更为准确的方法；(2)基于水槽实验和三维水气两相流紊流数学模型数值模拟结果，建立了新的丁坝前奎水高度计算公式；(3)基于上述奎水高度计算公式和本文二维水面计算数学模型，首次提出了丁坝上下游二维水面分段计算方法。

Three turbulent models used recently have been analyzed. On the basis of turbulent random theory, the k-εtwo equations turbulent model has been modified by nonisotropic hypothesis, to accommodate the nonisotropic property of flow field.

重新推导了雷诺应力表达式，将湍动粘性系数用一个二阶张量形式表示，以适应流场的各向异性性质，并对ε输运方程的生成项做了修正。

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。

In order to reduce the skin friction efficiently,more research works should be done on the characteristics of turbulent boundary layer,turbulent coherent structures and the mechanism of turbulent drag reduction for flow over riblets surfaces.

为更有效地减少表面摩阻，必须深入开展对沟槽面湍流边界层特性、湍流拟序结构及湍流减阻机理等方面的研究。

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。

In the future, some issues need to be investigated further, which include: establish and study the low-dimensional dynamical system of turbulent jet, with the POD bases, the control of turbulent jet based on the low-dimensional dynamical system of turbulent jet, investigate the physics mechanism of intermittence shed-off of the vortex ring in turbulent jets in crossflow.

有待进一步研究的问题是：建立基于POD模的湍流射流低维动力系统，并对其进行分析；研究基于湍流射流低维动力系统的湍流射流控制；探讨湍流横向射流中涡环间歇脱落的物理机制。

It has been put forward that there exists single Ball point and double Ball points on the symmetrical connecting-rod curves of equilateral mechanisms.

从鲍尔点的形成原理出发，分析对称连杆曲线上鲍尔点的产生条件，提出等边机构的对称连杆曲线上有单鲍尔点和双鲍尔点。

The factory affiliated to the Group primarily manufactures multiple-purpose pincers, baking kits, knives, scissors, kitchenware, gardening tools and beauty care kits as well as other hardware tools, the annual production value of which reaches US$ 30 million dollars.

集团所属工厂主要生产多用钳、烤具、刀具、剪刀、厨具、花园工具、美容套等五金产品，年生产总值3000万美元，产品价廉物美、选料上乘、质量保证，深受国内外客户的青睐