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1.
载人列车车厢内空气流场温度场数值模拟   总被引:4,自引:0,他引:4  
采用稳态不可压缩雷诺时均N-S方程、k-ε湍流模型,计算了载人列车车厢内三维空气流场和温度场。将太阳辐射热和人体散热作为能量方程的附加源项,研究了在条缝送风条件下,乘客和太阳辐射对车厢内流场和温度场的影响。计算结果表明:现有的送风方式除车厢两端外,车厢内沿长度方向气流分布比较均匀;送风口的布置对车厢内流场温度场分布影响较大,送风气流在车厢两侧形成两股比较大的流动旋涡;人体散热和太阳辐射对车厢内流场温度场影响较大,非空载时车厢内流场分布与空载时有较大差别,太阳照射和人体产生的热气流使车厢内存在较大的温度梯度,靠窗处的温度较高,过道处温度较低。流场温度场的计算结果和实验数据吻合较好。  相似文献   

2.
长途旅行中的睡眠区气流组织设计对于人体热舒适和空气质量控制是极其重要的。为了给小空间睡眠区提供更加舒适和空气质量更佳的气流组织,本文首次针对置换通风、个性通风、混合通风三种通风方式,利用CFD(计算流体力学)对睡眠区速度场、温度场、污染物CO2的浓度分布进行了数值模拟分析。对利用CFD计算出的面部舒适速度比例(FSR)、吹风感(DR)、空气龄(MA)进行比较,得出:在睡眠区采用个性送风可以在最节能的情况下得到更好的面部舒适速度比例和空气质量,优于置换通风和混合通风;1.5m3/min为个性通风的最佳通风量;为了避免在睡眠区使用个性通风时产生吹风感,应该保证送风温度不能过低;增大个性送风口送风面积可以有效降低吹风感。  相似文献   

3.
环境热舒适是衡量建筑物等级的重要指标。据大量实验与现场研究表明,PMV热舒适模型存在一定的偏差,有待完善、改进。现有PMV计算模型计算的各散热项、热负荷、PMV值与实际存在偏差;适用于PMV评价模型“接近热中性”环境条件、人体热负荷定义及其计算方法还存在异议。通过理论分析,本研究提出了新的“接近热中性”环境条件、新的人体热负荷定义及其计算方法,提出了新的PMV计算模型,并经对比分析发现,新的模型修正了在偏热环境下的现有PMV预测偏差。另一方面,在新的热负荷计算方法下,PMV与热负荷之间的函数关系KM必须进行相应调整,要获得准确的KM函数关系,必须获得较准确的人体平均皮肤温度与环境参数间的关系。  相似文献   

4.
针对驾驶室热舒适性评估与优化的问题,采用基于Fluent二次开发的用户自定义函数对驾驶室热舒适性进行仿真分析。结合国际热舒适性通用指标预计平均热感觉指数和预计不满意率对驾驶室的热舒适性进行了定量分析,并探究了送风方式和送风温度对驾驶室环境热舒适性的影响规律。结果表明:顶部送风相比于前部送风可以更好地改善驾驶室环境的热舒适性,而且保证人体各部位及驾驶室整体热舒适感分布均匀,送风温度相较于送风方式对驾驶室热舒适性的影响更为显著。  相似文献   

5.
短脉冲激光加热引起材料内部复杂的传热过程及热变形,现有的以Fourier定律或Cattaneo-Vernotte松弛方程结合弹性理论为框架建立起来热应力理论在刻画其热物理过程存在严重缺陷. 本文基于分数阶微积分理论, 以半空间为研究对象, 建立了分数阶Cattaneo热传导方程和相应的热应力方程, 给出了问题的初始条件和边界条件, 采用拉普拉斯变换方法, 给出了非高斯时间分布激光热源辐射下温度场和热应力场的解析解, 研究了短脉冲激光加热的温度场及热应力场的热物理行为. 数值计算中, 首先对理论解进行数值验证, 然后取分数阶变量$p=0.5$研究温度场和热应力场的变化特点及激光参数对温度和热应力的影响,最后数值计算分数阶参数对温度和热应力场的影响. 计算结果表明, 分数阶Cattaneo传热方程和热应力方程描述的温度和热应力任然具有波动特性,与经典的Fourier传热模型和标准的Cattaneo传热模型相比, 分数阶阶次越大, 热波波速越小, 热波波动性越明显; 反之, 则热波波速越大, 热扩散性越强.激光加热和冷却的速度越快, 温度上升和下降的速度越快, 压应力和拉应力交替变化越快, 温度变化幅值越小, 热应力幅值影响不明显.   相似文献   

6.
试件端面效应直接影响试件内的应力分布、试件破坏形式和剪切带图案。采用FLAC - 3D模拟了端面效应对岩石试件剪切带图案、速度场和位移场的影响。试样端部的缚束作用较强时 ,仅在试样中部出现X形的剪切带 ;反之 ,在试样端部出现了倾斜的剪切带。压头刚性越大 ,剪切带倾角越大。块体具有整体平移的特性 ,剪切带边缘位移梯度却较大 ,反映了块体沿剪切带发生滑动的剪切破坏本质。数值模拟结果可在众多的试验结果中找到佐证。  相似文献   

7.
吴迪  赵宝生 《应用力学学报》2012,29(4):349-352,481
为了得到精确的应力场、位移场、温度场,将扭转圆轴的精化理论研究方法推广到轴对称横观各向同性热弹性圆柱。利用Bessel函数以及轴对称横观各向同性热弹性圆柱的通解,给出了轴对称横观各向同性热弹性圆柱的分解定理。根据柱面齐次边界条件获得了精确的精化方程,精化方程可以分解为一阶方程、超越方程、温度方程,从而将横观各向同性热弹性圆柱的轴对称问题分解为轴向拉压问题、超越问题、热-应力耦合问题。超越部分对应端部自平衡情况,可以清晰地了解到端部应力分布对内部应力场的影响,热-应力耦合部分对应无外加应力场时圆柱内部因温度变化引起的热应力。  相似文献   

8.
黄鹏  莫军  符春渝  魏晓贞 《实验力学》2005,20(Z1):60-64
研究含切口部件的应力集中现象具有一定的工程价值,本文采用基于电子散斑干涉(ESPI)技术的Q100系统测试板材切口端部的位移场和应变场,同时采用弹塑性有限元方法予以分析;应变场ESPI试验结果反映了切口端部的应变局域化现象,横向和轴向应变的ESPI测试结果和计算结果变化规律一致,但有限元计算的切口端部应变分量变化梯度更大.  相似文献   

9.
在试验研究的基础上,对Q460高强钢螺栓横排和纵排连接接头的应力分布、破坏模式、螺栓受力及承载性能进行了有限元模拟,并与EC3规范关于孔壁承压、螺栓抗剪、净截面破坏及板件撕裂的理论计算值进行了对比。研究结果表明:有限元分析的荷载位移曲线规律及连接接头的极限承载力与试验结果基本吻合。当螺栓横向布置时,两孔受力较均匀,应力云图及塑性区域呈对称分布,拟合曲线点分布较离散,采用EC3规范理论计算值富裕度较大;当螺栓纵向布置时,两孔受力不均,端部螺栓孔变形较大,EC3规范计算端部螺栓和中部螺栓承载力均比较准确。本研究可为高强钢螺栓连接设计方法提供数据参考。  相似文献   

10.
基于Laplace变换及特征值法,推导并给出了分数阶广义热弹性理论下中空柱内表面作用有热冲击情况的解析解,通过Laplace数值逆变换法求解得到了位移场、温度场、应力场的分布规律。结果表明:特征值法能准确给出Laplace域内方程组的解;分数阶参数对温度场和应力场有较大影响,对位移场影响较小。作为广义热弹性理论的一种推广,在处理热传导问题时,通过分数阶广义热弹性理论进行研究更科学、全面。  相似文献   

11.
鼻腔加温功能特征及其与气流场关系的研究   总被引:1,自引:0,他引:1  
为研究鼻腔加温功能特征及其与气流场之间的关系, 选用1例健康国人的鼻腔进行CT扫描. 据CT数据对鼻腔气道进行表面三维重建, 运用计算流体动力学方法分析通气量为12L/min时吸气相0.15s, 0.45s, 0.75s的鼻腔气流场与温度场. 结果显示吸气相0.15s, 0.45s, 0.75s鼻腔气流场主要表现为双侧气流量分布不对称, 其中气流主要流经左侧; 双侧均为总鼻道中、下部气流量较多, 嗅裂、中鼻道和下鼻道气流量少. 吸气相0.15s, 0.45s, 0.75s温度场均表现为温度自鼻腔前端至鼻咽部逐渐增高, 其中温度主要上升区域为鼻内孔-下鼻甲前端-中鼻甲前端对应气道, 且在吸气速度和流量增大后, 这一主要加温区域无明显向后延长征象; 双侧鼻腔及单侧鼻腔不同部位气道气流分布差别较大, 但双侧温度场基本对称, 单侧鼻腔不同气道部位温度差值亦较小, 幅度均小于1℃.  相似文献   

12.
In this paper, we analyze an improved suspension system with the incorporated inerter device of the quarter-car model to obtain optimal design parameters for maximum comfort level for a driver and passengers. That is achieved by finding the analytical solution for the system of ordinary differential equations, which enables us to generate an optimization problem whose objective function is based on the international standards of admissible acceleration levels (ISO 2631-1, Mechanical Vibration and Shock—Evaluation of Human Exposure to Whole-Body Vibration–Part 1, 1997). The considered approach ensures the highest level of comfort for the driver and passengers due to a favorable reduction in body vibrations. Numerical examples, based on actually measured road profiles, are presented at the end of the paper to prove the validity of the proposed approach and its suitability for the problem at hand.  相似文献   

13.
A numerical solution of the unsteady free convection on an isothermal horizontal circular cylinder whose temperature is suddenly increased is presented at large Grashof number. Solutions for simultaneous development of the momentum and thermal boundary-layers are obtained by using the local non-similarity solutions method, together with the difference-differential procedure. The transient approach of velocity and thermal fields to the ultimate steady state and the variations in time of wall shear and heat transfer coefficients were found. The results at the lower stagnation point of the cylinder for Prandtl number Pr=1.0 are seen to improve the previous study of Hermann [1].  相似文献   

14.
Numerical and experimental methods were used to explore temperature and pressure distributions inside an irregularly-shaped cavity of a novel three-dimensional space environment simulator (SES) system. In order to obtain better temperature and pressure distributions, a plenum chamber and airflow diffusion perforated plate were adopted. Three-dimensional heat and mass transfer characteristics were analyzed using the Standard kε turbulence model. Simulation results revealed that the temperature and pressure distributions were greatly improved with improved diffusion configuration design, the temperature gradient decreased from 5 K to 1 K, and the pressure gradient decreased to 0.5% of the former value. Based on the simulation results, an improved experimental system for simulating space environment was set up. This experiment system could supply airflow with temperature ranging from 193 K to 353 K for simulating the real space environment. Experimental results showed that the temperature and pressure fields had smaller gradients across the surface and the inner cavity, which agreed considerably with the numerical results. The results of this study present useful information for the design of similar cavity structure.  相似文献   

15.
To investigate the effect of near-wall heat-source shape on particulate motion, the particulate distribution and deposition in a ventilated chamber with different heat-source configurations were numerically modeled. Using the discrete random walk model of the Lagrangian method, the trajectories of 3200 mono-disperse particulates ranging from 1 to 10 μm with a density of 1400 kg/m3 were tracked. Airflow pattern, temperature fields, the distribution of particulate concentrations, and deposition patterns are calculated and presented. The results show that the shape of a near-wall heat source has an influence on the airflow as well as the temperature field in the chamber and hence affects the particulate distribution and deposition.  相似文献   

16.
This study considers numerical simulation of the combustion of hydrogen with air, including oxygen and nitrogen, in a burner and the numerical solution of local entropy generation rate due to the high temperature and velocity gradients in the combustion chamber. The effects of equivalence ratio (ϕ) and oxygen percentage (γ) on the combustion and entropy generation rate are investigated for different ϕs (from 0.5 to 1.0) and γs (from 10 to 30%). The combustion is simulated for the fuel mass flow rate providing the same heat transfer rate to the combustion chamber in the each case. The numerical calculation of combustion is performed individually for all cases with the help of the Fluent CFD code. Furthermore, a computer program has been developed to calculate numerically the volumetric entropy generation rate distributions and the other thermodynamic parameters by using the results of the calculations performed with the FLUENT code. The calculations bring out that the increase of ϕ (or the decrease of λ) reduces significantly the reaction rate levels. The average temperatures in the combustion chamber increase about 70 and 23% with the increases of γ (from 10 to 30%) and ϕ (from 0.5 to 1.0), respectively. With the increase of γ from 10 to 30%, the volumetric local entropy generation rates decrease about 9 and 4% in the cases of ϕ=0.5 and 1.0, respectively, and while the total entropy generation rates decrease exponentially, the merit numbers increase. The useful energy transfer rate to irreversibility rate therefore improves as the oxygen percentage increases.  相似文献   

17.
During the machining of metals, plastic deformation and friction lead to the generation of heat in the workpiece, which results in thermomechanically coupled deformation. Recently, several numerical models of this highly coupled process have been produced in response to increased interest in high speed machining. It is important to characterize the thermal field in the cutting zone in order to completely verify these models of high speed machining and to direct further advancement in this area. In this work, HgCdTe infrared detectors are used to experimentally measure the temperature distribution at the surface of a workpiece during orthogonal cutting. From these temperature measurements, the heat generated in the primary shear zone and the friction zone can be examined and characterized. A modified Hopkinson bar technique has been developed to perform orthogonal machining at speeds ranging from 10 to 100 m/s. In the present work, a cutting velocity of 15 m/s is employed in all the tests in order to demonstrate the capability of the apparatus and characterize thermal fields during low speed machining. Temperature fields are obtained during the orthogonal cutting of aluminum as a function of depth of cut. It is seen that depth of cut can vary both the maximum temperature as well as the distribution of the temperature field in the aluminum workpiece. the maximum temperature increased with depth of cut (238°C for 1.5 mm cut, 207°C for 1.0 mm cut and 138°C for 0.5 mm cut) and the temperature field extended further beneath the cut surface with decreasing depth of cut.  相似文献   

18.
Ultrasound thermometry in transparent and opaque fluids   总被引:1,自引:0,他引:1  
We have exploited the temperature dependence of sound velocity to measure the thermal fields in transparent and opaque fluids. A chamber containing glycerol undergoing Rayleigh–Bénard convection was probed with an ultrasound transducer operating in the pulse-echo mode. The times-of-flight for the ultrasound pulse to traverse the fluid at several transducer locations were converted into a temperature profile that is in qualitative agreement with simultaneous thermochromic liquid crystal visualization of the flow pattern. Temperature profiles in a mercury-filled stainless steel chamber have also been obtained, both for quiescent and turbulent flows, thereby validating the ultrasound thermometry concept for opaque fluids as well.  相似文献   

19.
甘振鹏  杨东 《力学学报》2022,54(3):577-587
亥姆霍兹共振器(HR)作为典型的被动消声装置, 常被安装于航空发动机和燃气轮机的燃烧室上用以吸收噪声进而抑制燃烧热声振荡. 在实际应用中, 为防止燃烧室内高温气体损坏HR, 常引入冷却气流从HR的背部空腔通过其颈部流入燃烧室, 以保护HR. 该冷却气流的温度一般显著低于燃烧室内的燃气温度. 将这样的HR安装到燃烧室上时, 该温差可能影响燃烧室中HR上、下游的声波与熵波关系, 并进而影响HR的吸声性能. 然而, 在以往研究HR对燃烧室内热声振荡的影响的模型中, 该温差的影响一般被忽略. 本文基于声类比的思想, 建立了一个可预测当带有冷却气流的HR被安装于一个一维声学管道中时的消声性能的理论模型. 该模型基于一维质量、动量和能量守恒方程, 在无黏性耗散作用, 忽略体积力、所有的外来热源和热扩散的假设下, 首次推导出了侧壁安装有带冷却气流的亥姆霍兹共振器的一维燃烧室中的带源项的波动方程. 该方程右侧的源项能体现出共振器对燃烧室内一维声场的影响, 通过该方程可以看到共振器所带来的声源/声耗散是由熵扰动与质量扰动项组成. 由此可以进一步看出由共振器温差所产生的熵扰动会以声源的形式进入燃烧室内的一维声波方程, 并显著地改变HR在其共振频率附近对燃烧室内声场的影响. 通过与已有的阶跃条件模型对比, 验证了该模型预测HR温差对管道内声场的影响的准确性.   相似文献   

20.
有限长滚子线接触热弹流润滑分析   总被引:8,自引:2,他引:6  
应用多重网格解法 ,求出了有限长滚子线接触热弹流润滑的完全数值解 .结果表明 :在滚子的中部 ,油膜压力、温度和最小膜厚与无限长线接触热弹流润滑的解几乎一致 ;在滚子端部的圆角处 ,油膜压力、温度和最小膜厚与中部均显著不同 ,且最大油膜压力、最大油膜温度和最小油膜厚度均发生在此处 ,端部圆角半径对弹流润滑性能有显著影响 .同时 ,将有限长线接触热解与有限长线接触等温解进行了比较 .  相似文献   

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