Rainfall – runoff modelling in the urban catchment of El Batan,Quito, Ecuador

ABSTRACT

Filling and emptying processes are common maneuvers while operating, controlling and managing water pipeline systems. Currently, these operations are executed following recommendations from technical manuals and pipe manufacturers; however, these recommendations have a lack of understanding about the behavior of these processes. The application of mathematical models considering transient flows with entrapped air pockets is necessary because a rapid filling operation can cause pressure surges due to air pocket compressions, while an uncontrolled emptying operation can generate troughs of sub-atmospheric pressure caused by air pocket expansion. Depending on pipe and installation conditions, either situation can produce a rupture of pipe systems. Recently, reliable mathematical models have been developed by different researchers. This paper reviews and compares various mathematical models to simulate these processes. Water columns can be analyzed using a rigid water column model, an elastic water model, or 2D/3D CFD models; air–water interfaces using a piston-flow model or more complex models; air pockets through a polytropic model; and air valves using an isentropic nozzle flow or similar approaches. This work can be used as a starting point for planning filling and emptying operations in pressurized pipelines. Uncertainties of mathematical models of two-phases flow concerning to a non-variable friction factor, a polytropic coefficient, an air pocket sizes and an air valve behavior are identified.     

基于百分位数法的中国不同强度小时降雨频次空间分异格局及其变化模态研究(1961-2013)

高分辨率的降水数据有助于科学认识全球增暖背景下不同强度降雨事件的空间分异特征。采用1961—2013年中国545个气象观测站的小时降水数据,基于50%和90%分位数,将小时降水事件分为弱降雨、中等强度降雨、强降雨和总降雨四类事件,从气候态特征、波动特征、变化趋势和时空变化模态四个方面诊断了上述四类小时降雨频次的空间演变特征。结果表明:(1)基于50%和90%分位数阈值的方法表明中国小时降雨阈值具有明显的东高、西低,沿海高、内陆低的空间分异特征。(2)中国不同强度小时降雨频次在1961—2013年呈现出东南高、西北低的空间分异特征,其中从东北至西南存在一个介于东南和西北之间的过渡带,其不同降雨频次介于东南和西北之间。(3)中国不同强度小时降雨频次波动特征首先呈现出东南波动小,西北波动大;其次呈现出南方波动小,北方波动大的空间分异特征。中国不同强度小时降雨频次均在长江流域呈现出增加趋势,强降雨和总降雨频次在京津冀地区也明显趋于增加。(4)基于EOF分析的结果表明中国不同强度小时降雨频次在长江流域趋于增加是最主要的模态特征,该模态小时弱降雨、中等强度降雨、强降雨和总降雨频次的方差解释率分别达62.49%、59.41%、46.26%和67.20%。     

A large‐scale experimentation of the smart sewage system

This paper presents a large‐scale experimentation of the smart sewage system, which is conducted at the Campus of Lille University. The campus stands for a town of about 25 000 users with 150 buildings and 100 km urban networks. The experimentation is carried out within a large‐scale demonstrator of the Smart City, which includes a smart monitoring of the drinking water, sewage, electrical and district heating networks. The originality of this paper lies in the integrated approach, which includes smart monitoring as well as data collection and analysis. The monitoring of the drinking water and sewage networks allows the use of numerical modelling of and the detection of eventual connection between the sewage and storm water systems. The paper shows how the smart technology could be implemented and used to enhance our understanding of the sewage system and to improve its management.     

基于成灾信息的山洪灾害临界雨量综合检验复核方法

山丘区小流域山洪灾害临界雨量计算时受到众多因素影响,有必要结合近期实际成灾暴雨洪水信息对临界雨量理论值进行检验复核。临界雨量检验复核通常针对某一防灾对象,而同一防灾对象通常有多个预警时段,为了判别防灾对象整体临界雨量的可靠度,利用近期成灾暴雨洪水信息计算各预警时段合理性判别因子,采用层次分析法(AHP)确定各预警时段合理性权重,计算合理性综合检验指标,检验防灾对象整体临界雨量的合理性。实例计算表明,合理性综合检验指标能有效判别防灾对象整体临界雨量的可靠度,完善了临界雨量合理性检验复核理论体系,且为小流域临界雨量检验复核提供了新的思路。     

Areal rainfall intensity distribution over an urban area and its effect on a combined sewerage system

The application of 21 pluviometers over the whole area of ?ód?, Poland, enabled an examination of areal distribution of intense rainfalls during 2010–2011. On the basis of collected data the distribution of rainfall intensity was analysed and a circular zone model with exponential shape in all directions has been proposed for describing rain storms. Also, the velocity of storm zone movement between 2 and 30 km/h was determined. Using the SWMM 5.0 software, adapted for non-standard use, runoff from three real catchments and combined storm overflow discharge was examined for selected measured rainfalls. An effect of storm zone range and movement was also studied for the same catchments using model storms. It was confirmed that using data from the city pluviometric network enables significantly better simulation results for CSO overflows to be obtained compared to an option based on a single pluviometric station, especially for large catchments greater than 200 hectares.     

Probabilistic runoff volume forecasting in risk-based optimization for RTC of urban drainage systems

This article demonstrates the incorporation of stochastic grey-box models for urban runoff forecasting into a full-scale, system-wide control setup where setpoints are dynamically optimized considering forecast uncertainty and sensitivity of overflow locations in order to reduce combined sewer overflow risk. The stochastic control framework and the performance of the runoff forecasting models are tested in a case study in Copenhagen (76 km² with 6 sub-catchments and 7 control points) using 2-h radar rainfall forecasts and inlet flows to control points computed from a variety of noisy/oscillating in-sewer measurements. Radar rainfall forecasts as model inputs yield considerably lower runoff forecast skills than “perfect” gauge-based rainfall observations (ex-post hindcasting). Nevertheless, the stochastic grey-box models clearly outperform benchmark forecast models based on exponential smoothing. Simulations demonstrate notable improvements of the control efficiency when considering forecast information and additionally when considering forecast uncertainty, compared with optimization based on current basin fillings only.     

East Asian-North Indian Ocean thermal contrast and variation in the East Asian summer monsoon for the past 2650 years

Using observational data,the East Asian-North Indian Ocean index(IEANI),which reflects a tropospheric thermal contrast,is found to correlate well with the East Asian summer monsoon(EASM) and associated rainfall over eastern China.Corresponding to a higher(lower) IEANI,the EASM at mid-latitudes is stronger(weaker),and there is more(less) rainfall in North China and less(more) rainfall near the Yangtze River valley.To investigate long-term variation in the EASM,we reconstructed the BC 665-AD 1985 IEANI based ...     

雨滴在船舶大气激光通信中的遮挡作用

虽然气候因素和大气本身对船舶大气激光通信系统的性能影响极大,但现有的研究多集中于讨论大气对激光束造成的散射衰减。本文指出在雨中的自由空间光通信主要受雨滴直接遮挡的影响,尤其是雨滴形成的投影间的重叠效应,该效应能够很好地解释大雨甚至暴雨中激光仍能通过的现象。文中结合雨滴尺寸分布模型,建立了船舶大气激光通信中雨滴遮挡作用的数理模型,对光在雨中的最大传输距离及其光强的衰减做了初步计算与实验。结果证明,该衰减模型是合理的,理论模型基本符合实验结果。该项研究为进一步探索船舶大气激光通信系统的性能奠定了基础。