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71.
Indoor airflow pattern is strongly influenced by turbulent shear and turbulent normal stresses that are responsible for entrainment effects and turbulence‐driven secondary motion. Therefore, an accurate prediction of room airflows requires reliable modeling of these turbulent quantities. The most widely used turbulence models include RANS‐based models that provide quick solutions but are known to fail in turbulent free shear and wall‐affected flows. In order to cope with this deficiency, this study presents a nonlinear k‐ε turbulence model and evaluates it along with linear k‐ε models for an indoor isothermal linear diffuser jet flow measured in two model rooms using PIV. The results show that the flow contains a free jet near the inlet region and a wall‐affected region downstream where the jet is pushed toward the ceiling by entrainment through the well‐known Coanda effect. The CFD results show that an accurate prediction of the entrainment process is very important and that the nonlinear eddy viscosity model is able to predict the turbulence‐driven secondary motions. Furthermore, turbulence models that are calibrated for high Reynolds free shear layer flows were not able to reproduce the measured velocity distributions, and it is suggested that the model constants of turbulence models should be adjusted before they are used for room airflow simulations. 相似文献
72.
计量供热系统变流量运行节能分析 总被引:4,自引:0,他引:4
阐述了循环水泵变频调速的节能原理,提出离心水泵相似定律的适用性和等效率曲线概念.通过提出输配管压损曲线概念,从理论上分析了计量供热变流量系统循环水泵常用的恒扬程控制和恒定最不利环路压降控制两种方案,认为恒定最不利用户资用压力方案节能效果较好. 相似文献
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通过四根后张预应力混凝土靠船桩的试验,并结合有限元分析计算,研究了张拉控制应力、混凝土强度、配筋率等对靠船桩的裂缝形态、裂缝闭合性能的影响。结果表明,采用高强度材料的预应力混凝土靠船桩作为码头的防冲设施是经济可行的,良好的裂缝闭合性能有助于提高靠船桩的耐久性。在试验和理论分析计算的基础上,对预应力混凝土靠船桩的张拉控制应力、混凝土强度等提出了设计建议。 相似文献
76.
X.B. Tu B. Jian S.J. Wang H.Y. Bian J. Wang S.G. Li 《Tunnelling and Underground Space Technology incorporating Trenchless Technology Research》2005,20(4):1106
Granite is commonly recognized as an ideal medium for underground construction. However, in the site investigation for Heimifeng Pumped Storage Power Station project, it was found that there are swelling behaviors induced by alteration in granite and eventually causing slaking and disintegration of rock blocks. The study shows that hydrothermal alteration in granite is primarily due to the intrusion of multi-phase igneous magma. The clay minerals, such as montmorillonite, chlorite, kaolinite, are the main causes for the swelling behavior of granite. In the exploratory adits, alteration was observed to occur mainly along faults or fractures in the rock masses and resulted in roof caving if water is present. Some of the highly altered borehole cores swell and crack within 24 h in water and eventually disintegrate completely. From the testing results on the samples, the maximum axial free swelling strain is about 1.2%, while the maximum axial confined swelling strain is around 0.1% with swelling stress less than 25 kPa. Under free swelling tests, 80% of swelling is completed within 24 hours. Under confined swelling condition, swelling process is completed within 1 h for some samples, with 80% of maximum swelling strain finished within around 22 h for most of the samples. Contraction of samples occurs after swelling completed. The strength of granite, reflected by deformation and elastic moduli, shear strength, decreases due to alteration. The deformation and elastic moduli are even lower compared to highly weathered rock. The shear strength is between that for highly weathered and slightly weathered rocks. The swelling characteristics of the altered rock present great challenges for support or lining during construction and operation stages. Support or lining shall be in place immediately after excavation. Since the rock may swell when encountering water, the shotcrete shall be designed accordingly. During the construction of access tunnel and caverns, water shall be drained in time. Drainage directly from surface shall be avoided so as to prevent floor heave. 相似文献
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仿古建筑要达到“古色古香”的艺术效果,外装饰工程质量是关键,为了很好地体现“浦东钦赐仰殿道观藏经楼”建筑的历史风格,通过对木制品、油漆和屋顶的质量控制,确保了该工程的艺术美感,重现了明清建筑风貌。 相似文献
79.
1临港新城盐渍土概况上海临港新城位于长江与东海交汇处的南汇嘴地区,于21世纪初围海造地33km2,用于建设洋山国际集装枢纽港的陆域服务区。临港地区的土不是“土壤”,它只是“成土母质”。从2002年起,临港新城先后委托上海交大农学院、上海市园林科研所和上海岩土所等作了土壤调查。从化验分析结果得知:该地区的pH值大,盐份组成以硫化钠为主,氯离子占阴离子总量的86.32%;EC值高;地下水埋深115~147cm,矿化度6.39~6.82g/l;土壤密度高,通气孔隙度低;土壤有机质平均含量低(见表1),非常不利于植物生长。临港新城主城区G1、X1道路绿化工程,于2… 相似文献
80.
本文根据作者最近所参与“北大附中重庆实验学校”的工程项目中的所见所闻,结合国内建筑市场的实际情况,探讨了中国建筑师在理想实现过程中,所面临的各种困难及其背后深刻的社会原因,希望借此启发一些正在为自己的理想而在日夜奋斗着的年轻建筑师们。为了形象地说明这些因素对一项优秀建筑项目的产生所起的作用,文中采用了量化的百分比评价体系。 相似文献