THE DUAL NATURE OF HYDROPEAKING RIVERS: IS ECOPEAKING POSSIBLE?

Philosophically, the natural flow regime concept is tremendously appealing; however, its application can be challenging for many biologists without the expertise or resources to handle such approaches on their own. This is particularly true on hydropeaking rivers, where incorporating natural flow is sometimes challenging. Additional challenges include our limited understanding of how individual flow components relate to geomorphic and ecological processes. Supplementary to environmental flow approaches is understanding that many hydropeaking rivers are ecologically two different rivers in one: the low flow and high peaking flow. Taxa that require a narrow range of water velocities or cannot withstand rapid changes in discharge would likely be eliminated or competitively disadvantaged under such harsh environmental conditions. As the low and peak flows diverge, the two rivers become increasingly different ecologically, and there will likely be fewer taxa that can withstand such abiotic variability. Deviations from a natural flow regime may result in new constraints on certain fishes and invertebrates, but this does not necessarily mean a loss of productive fish habitat. Viewing hydropeaking rivers as two rivers in one and the risks associated with high to low flow ratios may serve as a more practical and useful perspective towards maintaining altered yet productive rivers while representing a step towards improving the management river ecosystems. © Her Majesty the Queen in Right of Canada 2013.     

CHARACTERIZATION OF GAS-LIQUID FLOWS IN RECTANGULAR BUBBLE COLUMNS USING CONDUCTIVITY PROBES

Unsteady gas-liquid flows in bubble columns are comprised of various flow processes occurring with varying length and time scales and govern mixing and transport processes. In the present work, we have characterized dynamic and time-averaged properties of gas-liquid flows in rectangular bubble columns using conductivity probes. The development of a single-tip conductivity probe, data processing methodology, and photographic validation procedure is discussed in detail. The effect of superficial gas velocity and aerated liquid height-to-width (H/W) ratio on voidage fluctuations and time-averaged gas holdup was investigated. The experimental data presented here can help in understanding the dynamics of various flow processes and validating computational fluid dynamics based models.     

黄登水电站泄洪消能试验研究

简述了黄登水电站可行性研究阶段枢纽泄洪消能防冲试验,水垫塘为定床和护岸不护底两种试验情况,对溢流表孔及左右岸放空底孔体型的优化。     

Evaluation of a single-capillary viscometer detector on line to a SEC system used with a new pulse-free pump

A single-capillary viscometer (SCV) used as an on-line viscosity-sensitive detector for size exclusion chromatography (SEC) presents considerable interest. Unfortunately, the commercially available version, which uses a traditional HPLC pump and a pulse dampener, presents serious problems and can give poor performance. Flow rate fluctuations are the main problems in the use of the on-line SCV detector. The pulse dampener resolves the flow fluctuations problems that are intrinsic to a reciprocating pump. Unfortunately, the pulse dampener introduces secondary, yet variable, flow fluctuations that make the SCV unreliable. In the past, several solutions to the problem have been described. Our proposal is to use the SCV on-line detector with a new commercial pulse-free pump without a pulse dampener. A detailed evaluation of this new SEC–SCV system has been performed using various polymers. Molar mass distribution, intrinsic viscosity distribution, and constants of the Mark–Houwink–Sakurada relationship have been determined. The used polymers were soluble both in organic solvent (PS, PMMA, PVAc, PVC, polyalkylthiofene) and in aqueous solvent (PEO, PEG, pullulan, and hyaluronan). The results obtained are encouraging. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1651–1659, 1998     

预报船体脉动压力的几种数值方法

研究螺旋桨空泡及其诱导的船体脉动压力的预报方法,对于减小其引起的船尾振动和辐射噪声是极其重要的.用螺旋桨非定常空泡的预报结果,在桨叶湿表面、空泡表面和尾涡面上布置强度已经求得的源和偶极子,用面元法计算得到无限流场中空泡螺旋桨诱导的速度势,进而求出船体表面的脉动压力.该方法还考虑了真实船体表面形状和自由液面条件,船体表面通过分布其上的奇点来模拟,通过映像法来考虑自由液面的影响.重点分析了船体表面上不同的奇点分布形式以及相应控制方程的区别,对几种方法的数值计算结果进行了比较,结果证明几种不同的数值方法计算得到的结果相差不大,可以任选一种计算公式进行计算.对一吊舱船的脉动压力进行了预报,并同模型试验结果进行了比较,两者有较好的一致性.     

Analysis of causes of erosion-corrosion wear of the metal of internal surfaces of watered regions of tubes of heat-exchange devices

Causes of the appearance of erosion-corrosion wear (ECW) on inlet regions of tubes of heat-exchange devices are considered. Experimental data are used for determining the mechanism of the ECW process and suggesting measures for its prevention. __________ Translated from élektricheskie Stantsii, No. 11, November 2005, pp. 56–62.     

城市中心区空间波动拓展及周期理论探析

通过测算南京等城市中心区发展过程,发现了城市中心区用地规模与用地强度指标增长的空间波动拓展现象。从形态学的角度对城市中心区空间形态波动拓展的深层次规律进行研究,提出中心区"规模-强度"交替拓展模型,即在市场经济的环境下,中心区通过自组织形成了其空间发展机制,使中心区交替处于外部扩张期与内部填充期,并表现为用地规模、用地强度两项指标的周期性交替增长。新街口中心区1978-2013年形态发展数据的量化实证研究证明,中心区空间规模的波动拓展与社会投资存在明显的互动规律。该拓展模型的运作可以解释为"溢出-回波"空间博弈、"收益-成本"经济博弈与"市场-政策"政策博弈三方面综合影响的结果,据此可为把握城市中心区的形态演化规律提供有益的参考。     

EVALUATION OF MINIMUM FLUIDIZING VELOCITY IN GAS FLUIDIZED BED FROM PRESSURE FLUCTUATIONS*

A new experimental method for the evaluation of minimum fluidizing velocity in gas fluidized beds is proposed based on the pressure fluctuations measurements. The minimum fluidizing velocity is determined solely from the measurements in the fluidized bed regime, unlike the traditional method, where experiments in the fixed bed regime are also necessary. Using the proposed method the on-line evaluation and prediction of the minimum fluidizing velocity is possible which is important for the control of industrial fluidized bed reactors.     

双尺度二阶矩颗粒湍流模型和提升管内稠密两相流动的模拟

稠密气固两相流动是当前国际上的研究热点,常常采用将颗粒湍流模型和反映颗粒碰撞作用的动力学模型叠加的办法来构造稠密两相流动的湍流模型。但是，对颗粒湍流模型，国内外尚没有进行双尺度湍流模型的研究。该文基于将颗粒脉动分成湍流引起的大尺度脉动和颗粒间碰撞产生的小尺度脉动的概念，建立了一种新的双尺度二阶矩颗粒湍流模型，并对提升管内的稠密气固两相流动进行了模拟。所得颗粒浓度及速度分布和实验数据吻合较好，能揭示出提升管内的环-核流动结构。该模型的结果比单尺度二阶矩两相湍流模型的结果有所改进。     

Characterization of gas fluidized beds of group C,A and B particles based on pressure fluctuations

Pressure fluctuation data were obtained with a quick response transducer at a sampling frequency of 100 Hz for periods of 100 s (i.e. 10,000 points) in order to characterize the gas-solid flow behaviour of fluidized beds of six powders. For beds of Geldart group B and group A particles, the occurrence and movement of bubbles caused vigourous pressure fluctuations of relatively large scale and weak dominant frequency. For beds of group C particles, on the other hand, pressure fluctuations were significantly smaller in scale and exhibited large dominant frequencies, with no clear formation of bubbles. The standard deviation of pressure fluctuations was markedly higher for the group A particles than for the group C powders. Group C particles could be characterized by gas voids and channels which exhibit periodic behavior, while beds of group A and B particles behaved in a less periodic manner and were dominated by more random and intensive bubble motion. Chaotic time series analysis was carried out for the six different species of particles. The Hurst exponent demonstrated differences between the three different powder groups. The two-phase character of gas-solids flow was more distinguishable for the group B and A powders than for the group C powders.