共查询到19条相似文献,搜索用时 687 毫秒
1.
2.
3.
4.
5.
6.
环形通道内空气湍流正在发展流与壁面辐射的耦合换热研究 总被引:1,自引:0,他引:1
对内环壁面加热、外环壁面绝热的圆环型通道,数值研究了空气湍流正在发展流与壁面辐射的稳态耦合换热。采用低雷诺数k-ε模型与SIMPLEC算法求解气流的湍流流动与对流换热,采用蒙特卡罗法求解壁面间的辐射换热,对流换热与表面间辐射换热通过绝热壁面边界条件进行耦合。通过模拟计算,分析了相关参数及物性变化的影响。研究结果表明,入口Re数与壁面发射率均对通道内的换热有重要影响;考虑空气物性变化与否所预测到的对流热流分布形态相差非常大,常物性下的模拟结果会导致对通道内热输运特性的不正确认识。 相似文献
7.
8.
9.
10.
11.
Yoichi KINOUE Toshiaki SETOGUCHI Mohammad MAMUN Norimasa SHIOMI Kenji KANEKO 《热科学学报(英文版)》2005,14(4):341-345
An experimental investigation was made into three-dimensional separated flow and the vortices within the flow separation in a decelerating channel flow generated by the suction from a porous side wall. The flows along the side and bottom walls were visualized by the surface tuft method. The turbulent internal flow was measured by the split-film probe to investigate the turbulent flow including the reverse flow. In the flow visualization for the strong decelerating flow (the suction flow ratio:0.8), two typical flow patterns appear alternatively. One is that the flow near the bottom wall separates more upstream than the flow near the top wall and a clockwise vortex can be seen in the separation region. Another is the reversal flow pattern with a counterclockwise vortex. By the turbulent flow measurement using the split-film probe, two peaks of turbulence level are observed for the strong decelerating flow case. These peaks can be related with two flow patterns mentioned above. 相似文献
12.
大机组轴承越来越多运行于紊流工况下,采用不同的紊流模型计算分析机组轴承的性能存在差异。该文目的是分析采用不同的紊流模型计算结果之间的差异,为选择紊流下轴承性能分析提供依据。该文对比了采用四种紊流模型对椭圆轴承性能的分析结果,包括最小膜厚、温升,流量、刚度阻尼等,并采用单元盘弹性转子一轴承模型讨论轴承的稳定性。分析结果显示,应该以分析目的和分析范围的不同来选择紊流模型。在稳定性分析中,采用青木弘模型计算结果比其他三种模型更趋保守;在轴承流量分析,对于纯紊流下分析可采用青木弘模型,对于层紊流过渡区可采用Ng-Pan模型。 相似文献
13.
G.A. Rivas E.C. Garcia M. Assato 《International Communications in Heat and Mass Transfer》2011,38(7):844-851
In the present work, the numerical simulation to calculate the problem of the turbulent convection with non-uniform wall temperature in a square cross-section duct was adopted. To solve this problem some assumptions for the flow, such as: the condition of fully developed turbulence and incompressible flow have been assumed. The methodology of the dimensionless energy equation was used to calculate the fluid temperature field in the square cross-section in function of the non-uniform wall temperatures prescribed. Numerical simulations were done using two different turbulent models to resolve the momentum equations and two more models to resolve the energy equation. The models of turbulence k-ε Nonlinear Eddy Viscosity Model (NLEVM) and the Reynolds Stress Model (RSM) were used to determine the turbulent intensities as well as the profiles of axial and secondary mean velocities. The turbulence model RSM was simulated using a commercial software. The thermal field was determined from other two models: Simple Eddy Diffusivity (SED), based in the hypothesis of the constant turbulent Prandtl number; and Generalized Gradient Diffusion Hypothesis (GGDH). In this last model, as the turbulent heat transfer depends on the shear tensions, the anisotropy is considered. These two last equation models of the energy equation of the fluid have been implemented in FORTRAN, a code of programming. The performances of the models were evaluated by validating them based in the experimental and numerical results published in the literature. Two important parameters of great interest in engineering are presented: the friction factor and the Nusselt number. The results of this investigation allow the evaluation of the behavior of the turbulent flow and convective heat fluxes for different square cross-sectional sections throughout the direction of the main flow, which is mainly influenced by the temperature distribution in the wall. 相似文献
14.
15.
为了研究两种体型齿墩式内消能工对管道内部水力特性的影响,采用FLUENT软件中的κ-ε数学模型模拟分析了齿墩内表面为平面(体型Ⅰ)和齿墩内表面为圆曲面(体型Ⅱ)两种体型消能工的流场、压力场、紊动能及水力参数等。结果表明,相同流速下齿墩内表面由曲面变为平面会扩大压强变化段长度和减小消能工出口处低压区的压强,且在大流速时体型Ⅰ在该区出现负压;消能工出口管壁附近会出现漩涡区,齿墩内表面由平面变为曲面,旋涡区域减小;紊动能的突变区域出现在消能工出口后,齿墩内表面由平面变为曲面会减小该区域的紊动能及其范围;齿墩内表面由平面变为曲面,消能工的消能率减小,流量系数加大,与其水力半径密切相关,为齿墩式内消能工的体型优化提供了依据。 相似文献
16.
17.
应用三维颗粒动态分析仪(3D-PDA)对方形下排气旋风分离器内气固两相流场进行了实验研究,并对流场、脉动速度、颗粒浓度、湍动能、湍流强度等的分布做了讨论。方形旋风分离器的流动具有Rankine涡 的特点,即中心部分为强制涡区,边壁附近是准自由涡区。边角处因颗粒与壁面间的相互碰撞引起的准层流运动,并使得颗粒湍流脉动强烈,湍流动能和局部湍流强度在边角附近取得较大值,表明此时两相流耗了气流的能量较多,是造成分离器压力损失的主要区域之一。边角有利于颗粒分离。研究结果为结构优化提供了基础数据,并为今后的数值模拟研究提供了实验对比。 相似文献
18.
通过修改发动机多维CFD计算程序KIVA-3V,建立了内燃机压缩过程冷态流场的大涡模拟(LES)计算模型.利用此模型对内燃机压缩过程中缸内流场的水平速度及湍流动能进行分析,同时,分析了网格密度对内燃机缸内流场大涡模拟的影响.结果表明,当采用k-ε模型计算时,网格的精细程度对流场结构影响不大;在相同的计算网格下,与采用k-ε模型计算相比,采用LES计算显示了更为复杂的湍流结构,而且LES所能捕捉到的涡团结构范围要大于k-ε模型,计算得到的湍流动能也要低于k-ε模型;同时,网格越精细,这种效应越明显. 相似文献
19.
JUNLI CHENG-KANGWU 《热科学学报(英文版)》1993,2(4):275-281
Flame stabilization in attachment jet combustors is based on the existence of the high temperature recirculation zone, provided
by the Coanda effect of an attachment jet. The single attachment jet in a rectangular channel is a fundamental form of this
type of flow. In this paper, the detailed characteristics of turbulent flow of a single attachment jet were experimentally
studied by using a 2-D LDV. The flowfield consists of a forward flow and two reverse flows. The forward one is composed of
a curved and a straight section. The curved section resembles a bent turbulent free jet, and the straight part is basically
a section of turbulent wall jet. A turbulent counter-gradient transport region exists at the curved section. According to
the results, this kind of combustor should have a large sudden enlargement ratio and not too narrow in width.
Project supported by the National Natural Science Foundation of China. 相似文献