Non-darcy free convection inside a wavy enclosure

Buoyancy induced flow and thermal fields characteristics inside a porous wavy walled enclosure have been numerically solved and analyzed. The enclosure consists of two isothermal wavy walls. The two parallel straight walls at the top and the bottom are flat and kept adiabatic. Governing equations are discretized using the Finite Element Method. Simulation was carried out for a range of surface waviness ratios, a = 0–0.5; aspect ratio, A = 2; inverse Darcy number, Da = 0.01–∞; and Rayleigh numbers, Ra = 10°–10⁷ for a fluid having Prandtl number equal to 1.0. Results are presented in the form of streamlines and isothermal lines for different values of surface waviness and porosity.     

高层建筑深基坑支护逆作法

以护坡墙与护坡桩组合，分段开挖，逐层推进，最后完成深基坑的围护，谓之“逆作法”。     

成朱联圩护岸中抛石固脚的设计与应用

结合工程实例对险段险情进行了成因分析,并从经济上和护坡机理上对抛投四面体透水框架的护坡方法做了简要分析,从而证明了“四面体透水框架抛投护岸方法”在边坡防护中有一定的使用价值．     

土石围堰高喷技术在龙滩水电站中的应用

为了论证龙滩水电站土石围堰采用高喷防渗在技术上的可靠性,工期上的可行性,施工方通过模拟土石围堰的地质条件进行了高喷试验,并取得高喷试验参数。详细论述了高喷试验方法、施工工艺及所取得的高喷成果。     

Experimental study of natural convection heat transfer in a semicircular enclosure

An experimental study of natural convection heat transfer in a differentially heated semicircular enclosure was carried out. The flat surface was heated and the radial surface was cooled isothermally. The effects of angle of enclosure inclination on the heat transfer across semicircular regions of several radii were measured for Rayleigh numbers Ra_R ranging from 6.72 × 10⁶ to 2.33 × 10⁸, using water as the working fluid. The angle of inclination varied from −90 degrees to 90 degrees with radii R of 50, 40, and 30 mm. The flow patterns were sketched from the results of a visualization experiment using aluminum powder. The temperature measurements in the enclosure were carried out using liquid crystals and thermocouples. The results indicate that different flow patterns were encountered as the angle of inclination varied, and the heat transfer rate was largely dependent on the flow pattern. In particular, enhanced heat transfer rates can be obtained when plume-like flow occurs along both hot and cold walls in the case of an upward-facing hot wall. Heat transfer for the inclined enclosure can be predicted using the equation for a vertical enclosure presented in this paper. © 1998 Scripta Technica, Inc. Heat Trans Jpn Res, 26(2): 131–142, 1997     

高原环境室内小型池火顶棚烟气质量浓度变化规律

运用燃烧相似分析中的辐射相似模型理论,在合理简化的前提下,推导了高原低压地区室内小型池火顶棚烟气质量浓度变化与常压地区的关系.理论分析表明,顶棚烟气质量浓度增长速率与气压的6次方成正比.结合国内外研究人员不同海拔地区的池火实验结果,在海拔高度范围40 ～3700m内(环境气压0.066～0.1 MPa)对理论关系式进行...     

Variations in microbial community during nitrogen removal by in situ oxygen-enhanced indigenous nitrogen-removal bacteria

In this study, the enclosure system exhibited perfect nitrogen removal performance with in situ oxygen-enhanced indigenous aerobic denitrifying bacteria in an enclosure experiment. We explored changes in the microbial community during the nitrogen removal process using the MiSeq high-throughput sequencing technology. The results revealed a total of 7974 and 33653 operational taxonomic units (OTUs) for water and sediment systems, respectively, with 97% similarity. The OTUs were found to be affiliated with eight main phyla (Proteobacteria, Actinobacteria, Cyanobacteria, Bacteroidetes, Planctomycetes, Chloroflexi, Firmicutes, and Actinobacteria). The diversity of the enhanced system was found to be higher than that of the control system. Principal component analysis (PCA) revealed that significant spatial and temporal differences were exhibited in the microbial community during nitrogen removal in the enclosure experiment. Redundancy analysis (RDA) indicated that physical parameters (temperature, dissolved oxygen, and pH), nitrogen (total nitrogen and nitrate), functional genes (nirK and nirS), and dissolved organic carbon (DOC) were the most important factors affecting bacterial community function and composition. Lastly, the results suggested that the variation in the microbial community could be analyzed through the MiSeq high-throughput sequencing technology, which may provide technical support for future field tests.     

Model for predicting performance of cooling fans for thermal design of electronic equipment (Modeling and evaluation of effects from electronic enclosure and inlet sizes)

This study describes the performance of cooling fans in terms of the P–Q curve and the maximum flow rate under various environmental conditions. It focuses on the relationship between fan performance and configuration factors such as the electronic enclosure. The presence of an enclosure wall increased the pressure characteristic of the fan performance. The presence of a narrow inlet decreased the flow rate. When the inlet area of the enclosure became smaller than twice the fan flow area, the flow rate was decreased. The maximum flow rate depended on the ratio of the inlet area to the fan flow area. A model for predicting pressure rise and flow rates in the enclosure is proposed. The model is used in a thermal analysis of a PCB model set in an enclosure. © 2011 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.20347     

The impact of various nanofluid types on triangular microchannels heat sink cooling performance

This paper discusses the impact of using various types of nanofluids on heat transfer and fluid flow characteristics in triangular shaped microchannel heat sink (MCHS). In this study, an aluminum MCHS performance is examined using water as a base fluid with different types of nanofluids such as Al₂O₃, Ag, CuO, diamond, SiO₂, and TiO₂ as the coolants with nanoparticle volume fraction of 2%. The three-dimensional steady, laminar flow and heat transfer governing equations are solved using the finite volume method. It is inferred that diamond-H₂O nanofluid has the lowest temperature and the highest heat transfer coefficient, while Al₂O₃-H₂O nanofluid has the highest temperature and the lowest heat transfer coefficient. SiO₂-H₂O nanofluid has the highest pressure drop and wall shear stress while Ag-H₂O nanofluid has the lowest pressure drop and wall shear stress among other nanofluid types. Based on the presented results, diamond-H₂O and Ag-H₂O nanofluids are recommended to achieve overall heat transfer enhancement and low pressure drop, respectively, compared with pure water.     

野外现场生态围隔实验研究进展

由于长江上游大量水电工程建设引起了很多河流水生态环境问题,河流型水华多次发生。介绍了一种在研究海洋或湖泊水华问题中常用的生态围隔实验方法,根据不同研究角度对围隔实验进行归纳分类,结合近几十年的研究文献分析其在水生态研究中应用的优缺点,并对围隔实验用于研究河流水华问题的可行性进行了展望。研究可为在长江河道开展生态围隔实验提供指导性建议。