Laboratory and Mathematical Modeling Aspects of Impurity Distribution in Permafrost Riverbeds

Power Technology and Engineering - The results of laboratory experiments on the distribution of impurity released by melting an ice plate placed in the coastal slope of a riverbed model in a...     

冰盖生长和消融的实验研究与数值模拟

为研究冰盖生长和消融的规律,在实验室内设计了水体结冰实验.通过实验得到冰盖厚度、水温和冰内温度随时间的变化过程.根据对水体结冰和融化物理过程的分析,建立水温与冰盖生长、消融相互作用的耦合模型.采用耦合模型来模拟水体结冰和融化过程,通过对模拟结果与实测结果的对比,发现冰厚和水温的计算值与实测值基本吻合.此结果为研究高海拔、高纬度地区封冻水库的结冰机制及冰盖下的水温时空分布提供重要理论基础.     

湖冰侧、底部融化现场观测与热力学分析

为深入了解湖冰在弱水动力条件下消融的热力学过程,在融冰期对乌梁素海湖开敞水域处冰层开展侧、底部消融的原位测量,并观测了太阳辐射、气/冰/水/泥温和风等气象及水文要素。观测结果表明冰层侧壁随深度增加逐渐向内侧倾斜融化,冰层厚度逐渐减薄;开敞水域处水温和冰温均呈分层变化,上层水温和冰温日变化幅度较大。通过分析冰层侧、底部融化速率与气象及水文要素之间的变化关系,建立了用净太阳辐照度和水温来表达融化速率的参数化模型。冰底热通量是一项重要的热力学参数,基于冰底薄层的能量平衡,利用观测数据确定了开敞水域处冰层的平均冰底热通量,为11.47~135.61W·m~(-2),表明冰下水体不断向冰层传递热量。     

冰下爆破预防冰坝的理论探索及实践

把冰、水、热动力学理论与爆破效果相结合,提出了在冰坝易发点沿深泓线实施冰下爆破形成温度场预防冰坝灾害的理论,包括:爆破时间的选择,爆破孔的布置,爆破效果的估计,温度场水温及下游冰盖下水温的影响长度和冰盖融化速率的计算。黑龙江开江期冰下爆破的实践表明,爆破坑平均直径随炸药量的增加而增加,但在炸药量超过18 kg时,爆破坑平均直径随炸药量的增加变化不大;根据实测单位炸药量破碎的冰盖体积的效果,建议冰下爆破预防冰坝的单孔炸药量应不超过9 kg,包括冰盖厚度超过1 m的情况。     

北大港水库水-土界面盐分释放规律研究

为了研究天津北大港水库水质咸化机理,采用野外取样与室内土柱试验相结合的方法,研究了北大港水库蓄水时底质与上覆水体之间盐分的释放规律。结果表明:底质向上覆水体释放盐分时水体中存在一个明显的盐分渐变区(扩散边界层),该层位于水-土界面以上10cm的范围,底质中释放出的盐分有60%集中在边界层,边界层以上水体盐分垂直变化较小;底质中盐分的累积释放量随时间的变化符合对数函数形式,试验运行前50天中盐分累积释放量占底质盐分总释放量的80%左右;水-土界面处盐分释放通量的变化趋势存在周期性,每个周期内均呈现先迅速增加后缓慢下降。     

A Modified Muskingum Flow Routing Model for Flood Wave Propagation during River Ice Thawing-Breakup Period

During the period of river ice thawing and breakup process (termed as “ice cover thawing-breakup”), vast amount of water stored in ice-covered river reach will be released comparing to that under open flow condition. The flow routing process during river ice thawing-breakup period will be different from that under open flow condition, since water stored in and channel from ice thawing-breakup process and flow routing process are very complicated. If the flow routing process during river ice thawing-breakup period can be predicted, it will very important for flood protection in the downstream river reach. In present study, water released from ice cover thawing process is considered as the lateral inflow to the channel flow during propagation process of flood wave from upstream to downstream. A model for the flood routing process during river ice thawing-breakup period has been developed based on the Muskingum hydrologic method. Using the modified Muskingum model, the routed outflow hydrograph has been determined along the Baotou Reach of the Yellow River during river ice thawing-breakup period. Results showed that the simulated hydrographs using developed model agree well with those of field measurements.

     

寒区水库冰盖形成与消融机理分析

根据对黑龙江省胜利水库冬季冰盖十余年资料的研究，考虑冰盖与大气、水的热交换过程及水库水温变化对冰盖厚度的影响等因素，建立了寒区水库冰盖生长的一维数值模型并给出了求解方法。与传统经验法相比，此模型考虑因素多，计算结果更符合实际，精度较高。同时还探讨了水库冰盖消融阶段冰压力沿深度分布规律、累积日平均气温与冰厚的关系和水库开库方式与累积气温的关系等。     

Ice accumulation and thickness distribution before inverted siphon

In winter, the safe operation and the water transfer efficiency of an inverted siphon are big concerns for water diversion projects in a high latitude area. This paper takes the Tanghe inverted siphon of the Middle Route of the South-to-North Water Diversion Project in China as an example, and carries out experimental studies under the real ice condition with different water levels, flow discharges and submerged depths. The ice accumulation process and the ice jam thickness distribution before the inverted siphon are tested and measured. The characteristics of the ice jam distribution and the relationship between /i t H(ratio of ice jam thickness i t to total water level H) and i Fr(Froude number under ice jam) are analyzed. An equation for the ice jam thickness calculation before the inverted siphon is put forward. Analysis results might help the thickness prediction and the ice jam prevention of similar water diversion projects during ice period.     

Detailed observation and measurement of sewer sediment erosion under aerobic and anaerobic conditions.

A greater understanding of the erosion behaviour of sewer sediments is necessary in order to reliably estimate the amount and nature of the sewer sediments released from deposits in sewers and transported either to waste water treatment plants or discharged into the environment. Research has indicated that microbial activity in sediment can influence the physical release of sediment from in-pipe deposits. This paper reports on a series of erosion tests in which sewer sediments from different sewer networks are kept under different environmental conditions and their resistance to erosion is examined. The erosion tests are carried out under aerobic and anaerobic conditions and two temperatures, one representing ambient sewer temperatures and a lower temperature that significantly suppresses bacterial activity.     

NUMERICAL TECHNIQUE FOR TURBULENT TIDAL FLOW FIELD WITH ICE COVERS

A numerical modelling technique for ice flowing and melting field in coastal tidal currents for the purpose of cooling water engineering design and research is presented based on k-ε turbulence mathematical model and the discretized moving-boun-dary-fitted coordinate system.Special attention is given to treat the complicate geometric,topographic and hydraulic conditions in natural estuarine water for the numerical simulation.The model therefore shows practical and efficient to cooling water engineering research.An engineering application has been conducted using the prediction on ice reduction and melting process by heated water discharges.     

Analysis of Polychlorinated Biphenyl (PCB) Loading Trends in Lake Michigan

PCB concentrations in coregonid fishes (bloater chubs) collected from Lake Michigan between 1972 and 1980 are used to infer an historical loading trend for polychlorinated biphenyls (PCBs). A mass balance model was developed to describe the dynamics of PCBs by assuming that historical fish concentrations are proportional to concurrent water column concentrations of PCB. The validity of this assumption is strengthened, since the data represent a single species of fish (a pelagic feeder), a specific age class of that species, and a single laboratory performing the collections and analysis of the data. The results of model analysis indicate that PCB loading to Lake Michigan during the period of observation can be described by a linearly decreasing trend. The calibrated model also forecasts the response of selected fish species to various loading scenarios. Forecast results indicate that a continuously decreasing load will result in compliance with U.S. and Canadian guideline value for human consumption by 1987. However, should PCB loadings not continue to decrease, compliance with the proposed U.S. and extant Canadian guideline of 2.0 mg/kg is doubtful. Forecast accuracy may be improved by the availability of precise measurements of water:fish distribution coefficients.     

Himalayan glaciers as a sustainable water resource

The Himalayan glaciers, which number around 15 000, cover an area of 33 000 km² and are nursed in the steepest and highest valleys in the world. Runoff from the seasonal melting of snow and ice contributes to the streamflows of the Indus, Ganga and Brahamputra river systems of the Indian subcontinent. The annual contribution from snowmelt and runoff from non‐glacierized areas during the early part of summer (April to June) amounts to 20%. As summer proceeds (July to September) the contributions from melting glacier ice and water stored within the glaciers reach 50%. In this paper the pattern of water release by melting and its chemical characteristics are described for a glacier in the Lahul‐Spiti valley of Himachal Pradesh, India.     

利用探地雷达探测黄河弯道及桥墩周围冰层厚度

黄河河道冻结结冰过程是黄河防凌汛研究的一个重点,进行弯道和桥墩周围冰层厚度的探测对防治冰凌灾害具有重要的意义。探地雷达对冰厚探测具有便携、高效、连续、快速、实时等优势。雷达天线的频率决定雷达波的穿透深度和分辨率。从雷达图像上可以清楚的识别空气-冰界面和冰-水界面。通过现场打孔测量冰厚数据反算雷达波在冰层中的传播速度进一步提高了测量结果的准确性。测量结果清楚的显示了弯道及桥墩处冰厚分布不均匀。桥墩北侧冰层较厚,弯道主河道处冰层较厚。200 MHz天线的探地雷达可以穿透黄河冰层,雷达图像可以清楚地显示冰-水界面。冰层厚度测量为分析黄河冰的冻结、融化过程以及冬春开河期冰塞、冰坝的治理提供了基础数据。     

水塘静水冰生消原型研究与数值模拟

为研究静水冰生长消融规律,2014年11月中旬至2015年3月中旬在内蒙古托克托县南湖水塘进行不同时段、不同水深静水冰生消的原型试验,通过试验观测得到冰盖厚度、水温和冰温随时间及气温变化过程。根据对水塘静水水体结冰和融化物理过程的分析,建立水温及冰盖生长、消融相互作用的耦合模型。结果表明:气温是静水冰盖生消的主要影响因素;在冰盖演变过程中,水深对其影响较小,仅对结冰后期冰厚及冰盖完全消融时间有所影响;表层水温受气温影响明显,深层水温受影响较小;冰面温度与气温变化同步。基于已有的数学模型,加入野外观测边界条件及气-冰-水三态热交换公式,模拟水温及冰盖生长和消融过程,发现冰厚和水温的计算值与实测值基本吻合,差值在波动允许范围内,此结果深化了对静态水域冰盖生效机理的认识。     

水塘静水冰生消过程及冰盖演变的原型试验

为研究静水冰生消过程及冰盖演变规律,于2014年11月中旬至2015年3月中旬对内蒙古自治区托克托县南湖水塘的冰情变化进行原型试验,研究不同时段气温、不同水深对静水冰生消过程、冰盖演变及水温分布、冰面温度的影响。试验结果表明:气温是影响静水冰情的主要因素,在冰盖增长期,冰厚与累积日均负气温线性相关;冰盖不稳定变化期和消融后期,冰厚及冰盖增长率主要受时段气温影响;水深对最大冰厚和冰融化消失时间有影响,对冰盖演变过程的影响不明显;气温变化对表层水温的影响较大,对深层水温的影响相对较小;冰面温度与气温变化同步。     

Research and application of in-situ control technology for sediment rehabilitation in eutrophic water bodies

Phosphorus (P) is often the limiting nutrient for algal growth, and P in sediments can be released under suitable conditions. To control P release, in-situ control technology with lanthanum (La) modified bentonite clay (Phoslock(?)) was proposed and its effectiveness was tested and evaluated both in laboratory and field trials. The results of static and dynamic simulation experiments under different environmental conditions showed that with the application rate of Phoslock(?) at 0.5 kg/m(2), the orthophosphate (PO(4)-P) concentration of the overlying water decreased to a low level (≤0.02 mg/L) within 10 days. Even under anaerobic and high pH (pH = 9.0) conditions, the phosphate release suppression efficiency reached 98.3%, and the P-release rate was -8.20 mg/m(2) d (negative value indicates P adsorption by Phoslock(?)). The monitoring data of the field sediments rehabilitation project were consistent with the results achieved in laboratory experiments, thus showing that the application of Phoslock(?) could inhibit the internal P release effectively.     

PCBs in Lake Superior, 1978–1980

Polychlorinated biphenyls (PCBs) were measured in the water column of Lake Superior during the summers of 1978 to 1980. The total PCB water concentrations were relatively uniform areally and vertically within any one year: 1978, 1.3 ± 1.3 ng/L; 1979, 3.8 ±1.9 ng/L; 1980, 0.9 ±0.4 ng/L. The volume-weighted abiotic PCB burden in the water column fluctuated with climatic conditions between ～10,000 and 40,000 kg, but would be in the range of 10,000 to 20,000 kg most of the time. Analysis of 24 large volume, filtered samples from 1980 showed that 27±12% of the PCBs were in the paniculate phase. The distribution coefficient for PCBs, defined by use of a glass-fiber filter, ranged from 10⁴ to 10⁷ L/kg, exhibiting a strong, inverse log relationship to the suspended solids concentration. This behavior is partially attributed to the differences in the organic carbon content of the sampled particles in different regions of the lake and to artifacts of the filtration process. The elevated total PCB concentrations in the summer of 1979 in conjunction with the previous winter's severe weather conditions are evidence of seasonal fluctuations of PCBs in the water column resulting mostly from sediment resuspension.     

PIV技术在冰盖下复式断面渠道流速测量中的运用

在测定冰盖下复式断面流场、流速的模型试验中,水体中的运动粒子是重点研究对象。粒子图像测速(Particle Image Velocimetry,PIV)技术已在水力学研究领域得到普遍应用,但该技术在冰盖下复式断面渠道模型试验的应用为国内首次。基于试验特点,设计砖砌混凝土的循环水箱,采用变频器配合水泵、流量计实现对流量的定量控制,对不同流量下不同断面的流场、流速进行测定,采用PIV技术对水体中运动的粒子的位移场进行具体分析。试验结果表明,PIV分析结果能够直观反映流场中的状态,且可以避免测量盲区,其所测的流速与多普勒超声测速仪测得值吻合较好,并给出了横向流速分布图,弥补了传统方法无法获得冰盖下的流场分布的难题。     

寒区均质土坝混凝土面板冰冻胀破坏的力学分析

为了研究寒区均质土坝混凝土面板在冰盖和土体冻胀共同作用下的受力和破坏问题,对北疆奎屯河流域和玛纳斯河流域几个大中型水库进行了野外实地调查。在此基础上,以柳沟水库均质土坝混凝土面板为研究对象,通过合理假设,运用力学基本理论对冰盖作用处混凝土面板的内力分布情况进行了分析。在力学分析的基础上,提出了面板发生冰冻胀破坏的判断准则。研究结果表明:库水面线附近弯矩最大,混凝土面板在该处容易发生断裂,裂缝往往是贯穿性的,并平行于库水面线。在冰盖作用处混凝土面板上部的接缝填充材料容易发生剪切强度破坏。     

2000年以来黄河宁蒙河段开河期冰凌洪水特点分析

黄河宁蒙河段开河期冰凌洪水主要集中在3月中下旬,一般由融冰洪水与冰坝洪水组成,其特点主要表现在:凌峰、洪量年际变化大,沿程增加明显,头道拐站易形成多峰,峰型系数较夏汛小,洪水历时较夏汛短,水位表现较夏汛同流量水位高,流速在涨水段慢于落水段。这些特点主要与宁蒙河道形态、水利工程、封河期上游来水及开河期气温、开河形势、封冻期形成的槽蓄水增量大小、沿程分布及其释放程度有关。