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关键词： classifications   Moran effect   population synchrony   Salmo trutta   spatiotemporal scales  

摘要： Investigating the variables driving synchrony in populations and the spatial scales at which they operate is worthwhile for both a basic understanding of population dynamics and for management. Various environmental classifications have been developed to group sites according to predefined similarities in abiotic variables (with spatial and/or temporal components) and to explain population dynamics in running waters. These classifications may be useful to managers and decision makers, as studies have shown relationships between time-dependent population variability and environmental classifications on different spatial scales. We investigated whether synchrony among brown trout (Salmo trutta) populations could be explained by three regional (hydro-ecoregions, hydrological units, and natural flow regime classification) and one local environmental classification and their associated variables. We first analysed whether densities of two size classes (0+ and >0+ fish) varied over a large spatial scale (i.e. 112 sites spread throughout France sampled for >11years). We then determined whether the degree of synchrony matched the spatial patterns defined by the environmental classifications. Finally, we investigated whether variables such as river distance between sites, hydrology, and temperature were associated with patterns of synchrony. Overall, relationships observed between synchronies in environmental variables and trout population densities were weak. Synchrony was best explained by the classification based on hydrological units, defined as discrete physical units that provided boundaries with real biological significance for river assemblages (12% for 0+ density and 9% for >0+ density and total densities). However, when considering environmental variables alone, synchrony in trout populations was mainly associated (from 11% to 23%) with seasonal flow variables such as high flows during reproductive and emergence periods. Temperature and river distance did not expla

关键词： Turbomachinery   Low-pressure turbine   Laminar-to-turbulence transition   Separation-induced transition   Secondary flow   Algebraic transition model  

摘要： The predictive qualities of a recently developed algebraic intermittency model for laminar-to-turbulent transition are analysed for the flow through a linear cascade of low-pressure turbine blades with an endwall. Both steady RANS (Reynolds-averaged Navier-Stokes) and time-accurate RANS (URANS) simulations are performed. The results are compared with reference LES (Large Eddy Simulation) by Cui et al. (2017, Numerical investigation of secondary flows in a high-lift low pressure turbine, Int. J. of Heat and Fluid Flow, vol. 63) and results by the local correlation-based intermittency transport model (LCTM) by Menter et al. (2015, A one-equation local correlation-based transition model. Flow Turbul. Combust., vol. 95) for laminar and turbulent endwall boundary layers at the cascade entrance. Good agreement is obtained with the reference LES and with results by the LCTM for the evolution through the cascade of the mass-averaged total pressure loss coefficient and for profiles of pitchwise-averaged total pressure loss coefficient at the cascade exit.

关键词： Two-phase flow loss   Solid rocket motor   Aluminized propellant   Particle size effect  

摘要： This study investigates the two-phase flow loss in aluminized solid rocket motor (SRM) by addressing the effects of particle size. A simplified axisymmetric 2D numerical simulation model is developed to simulate the flow field of the SRM, in which the two-phase flow consists of seeded inert Al2O3 particles and burned gas. The numerical model is verified by lab-scale SRM tests. The results show that the numerical simulation predicts SRM performance accurately when quantitatively capture the true particle size. Based on numerical simulations over a broad range of particle diameters, the effects of particle size on the gaseous phase and particle velocity distributions, particulate trajectories, and the thrust coefficient are systematically examined. It is found that with the same mass content of inert particles the two-phase flow loss decreases with increasing particle size.

关键词： Circulating fluidized bed   Two-phase flow   Discrete element method   Parallel cyclones   Numerical simulation  

摘要： The design and operation of circulating fluidized bed (CFB), which offers excellent heat and mass transfer, remain challenging because of the lack of a comprehensive understanding. CFD-DEM is used here for the high-fidelity simulation of the three-dimensional full-loop CFB with six parallel cyclones. Detailed information on the particle-scale information (i.e., solid dispersion, particle rotational speed, fluid and collision forces, mass distribution, and backing-mixing intensity) throughout the CFB are presented for the first time. Interesting results include: (i) the solid dispersion behavior is significantly different among the three directions;(ii) the solid loading in the middle cyclone on one side of the riser is twice that of the two adjacent ones, and this non-uniform distribution underscores the need for full-loop simulation for the CFB with multiple cyclones;(iii) the solid dispersion coefficients in all three directions, fluid force, collision force and particle rotational speed are similar among the six cyclones and correspondingly the standpipes;and (iv) approximately 50% and 48% of the total material are distributed respectively in the riser and standpipes. The results obtained provide valuable insights regarding the mass loading, particle-scale characteristics and non-uniform distribution of the solid phase throughout the entire CFB.

关键词： gas-solid fluidized bed   biomass mixture   concentration profile   mixing dynamics   bubble movement  

摘要： Aiming to better understand the biomass pyrolysis and gasification processes, a detailed experimental study of the mixing characteristics is conducted in a fluidized bed with binary mixtures. Rapeseed is used as biomass, and silica sand or resin as inert material. The effect of mixture composition, initial packing manner, and superficial gas velocity on the concentration distribution is investigated in a rectangular fluidized bed by means of photography and sampling methods. The results show that the mixture composition plays an important role in the axial solids profile of binary mixtures. The mixing behavior of binary mixture is dominated by the bubble movement. The axial distribution of binary mixtures becomes uniform with increasing superficial gas velocity, whilst no obvious effect of initial packing manner is observed in this study.

关键词： 水轮发电机   铁心过热   通风试验   故障排查  

摘要： 自一里水电站于2004年投产发电,2016年在对1号机组A修时发现发电机定子铁心端部有过热现象,为彻底查找铁心过热根源,对1号发电机进行了通风试验。文中介绍了采用传统风速仪检测和皮托管检测2种试验方法,从试验数据的准确性和可靠性方面,阐述了采用皮托管试验法得出的数据更符合发电机实际风场分布,为发电机定子铁心端部过热故障原因分析和后期发电机技改提供了有力的数据支撑。

关键词： 斑岩型铜矿   岩浆活动   流体特征   南秦岭  

摘要： 池沟地区小斑岩体广泛发育,岩体多呈北东向展布的串珠状小岩株或岩枝产出,属燕山期高钾钙碱性系列I型花岗岩。池沟斑岩型铜钼矿(化)体产于燕山期中酸性岩体内外接触带中,池沟区内岩体锆石UPb年龄为140~148 Ma,与矿石辉钼矿的Re-Os年龄一致,成岩与成矿年龄一致,均形成于侏罗纪晚期。池沟矿区成矿物质主要来源于侵入岩浆,铜矿体主要赋存于斑岩体及其与围岩接触带上,远离岩体,矿化减弱,矿体产状多受岩体与围岩接触面控制。近年来,通过对区内池沟岩体的研究,应进一步查明成矿主岩体的分布形态以及矿化富集规律,同时开展新的地质找矿方法,为柞-山盆地寻找铜矿提供新的思路。通过钻孔深部工程,在岩体内外接触带上寻找矿化富集部位应有较好的找矿前景。

关键词： 岩石分类   神经网络   FZI   指数   流动单元  

摘要： 储层流动单元划分对认识油藏的非均质性、注水开发效果和剩余油分布规律研究提供了有效手段。EP-A油田处于开发初期,存在两个问题有待解决:一是没有明确的孔渗关系,如果使用单一的孔渗关系计算渗透率,储层非均质性会被忽略,开发过程中历史拟合和开发指标预测也会受到影响;二是如何将岩石分类结果运用在三维地质模型中。本次研究运用岩心观察和实验数据进行岩石类型精细划分,共分为三类,每一类岩石类型给予相应的孔渗关系,并运用相应的孔渗关系计算渗透率,解决了储层非均质性无法准确表征渗透率的难题。在取心井上建立岩石类型与电性特征的关系,采用神经网络方法运用到非取心井中,进而运用到三维地质模型中,通过流动带指数(FZI指数)进行流动单元划分,从而有利于动态历史拟合,使下一步调整井的开发指标预测更加合理,降低了潜在开发风险。