机载雷达在黄河稳封期冰厚测量中的应用

为提高稳封期河道冰厚的测量效率,利用机载雷达对黄河内蒙古什四份子弯道进行了冰厚测验,并与量冰尺实测冰厚进行了对比。结果表明,什四份子弯道稳封期凹岸一侧冰厚范围在50～90 cm左右,比凸岸一侧冰厚约厚10～30 cm;清沟两侧冰厚分布一致,平均约50 cm,离清沟越近冰厚越小。机载雷达的测冰效果,平封冰盖最好(绝对误差小于5 cm)、立封冰盖次之、堆积冰盖最差,雷达实测冰厚与量冰尺实测冰厚的标准差为0.039 4,随机不确定度为7.88%,满足冰厚观测规范要求。机载雷达能快速对较大尺度的冰厚区域进行连续测量,极大地提升了冰厚的测验效率,可应用于黄河稳封期的冰厚测验。     

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。     

黄河河道冰层雷达波特征图谱的现场实验研究

2013年-2014年冬季,利用RIS K2型探地雷达在内蒙古头道拐水文站黄河河道断面开展冰层厚度探测试验。试验使用不同频率天线探测冰厚,并与钻孔实测冰厚对比。结果显示200 MHz频率天线可探测到冰下更深部位的状况,并能够识别出冰花层。利用雷达探测图谱中电磁波传播时间和实测冰厚得到盛冰期雷达电磁波在冰内的实际传播速度为16.3cm/ns;而融化期雷达电磁波在冰内的实际传播速度小于15.0cm/ns。雷达探测结果还显示垂直于河道断面方向的冰层厚度分布不均匀。主流区是以热力学生长的颗粒冰和柱状冰为主,最大冰厚约为60cm;而非主流区是以冰花冰为主,最大冰厚约为70cm。另外,雷达图谱也可以确定冰层裂缝的具体位置、走向。     

Simulations of ice jam thickness distribution in the transverse direction

River ice often forms in the cold regions of northern hemisphere which can lead to ice jams(or ice dams). Water level can be significantly raised due to ice jams. As a consequence, disastrous ice flooding may be resulted, such as the ice jam flooding in the Nechako River in Prince George in winter 2007-2008. In the present study, the equations describing the ice jam thickness in the transverse direction are derived. The impact of the secondary vortex is considered while the cohesive force within ice cubes is neglected in the model. The relationship between the parameter β and the total water depth is established based on the assumption that all other variables except the velocities are kept constant on the same cross section. By using the parameter β and the developed equations, the ice jam thickness in the transverse direction can be predicted. The developed model is used to simulate the ice jam thickness in the transverse direction at the Hequ Reach of the Yellow River in China. The simulated ice jam thicknesses agree well with the field measurements on different cross sections.     

黄河头道拐站开河日期预测的LSSVM方法

根据实测冰情数据分析发现,可将冰盖厚度演变过程作为预测头道拐站的开河日期的主要依据,同时还应考虑封冻期气温、流量等对冰盖厚度的持续性和累积性影响。据此提出了一种应用数据挖掘技术和LSSVM进行头道拐站开河日期预测的新方法。应用LSSVM模型对头道拐站2010年、2011年和2012年开河日期的预测结果表明,可在封冻期内任一冰盖厚度测量日期利用上述方法对该站的开河日期进行预测,有效延长了预见期,且在3月6日前的预测值均满足许可误差合格率的要求。根据LSSVM模型预测误差呈波动性变化的特点,提出了预测开河日期的均值法,可使开河日期预测精度得到显著提高。     

大庆水库冰表面温度特征及其在冰工程实践应用方法探讨

根据冰面热平衡方程并以大庆红旗泡水库冰面观测的气温、太阳辐射、风速、相对湿度、冰厚数据以及水库附近安达气象站记录的云量、湿度和海平面气压数据,求解了2009/2010年度冬季的冰表面温度,并分析了冰表面温度特征及其同太阳辐射之间的关系、同气温、风速之间的响应关系。在此基础上,就传统考虑的抗冰工程设计所需的设计冰表面温度进行了评估;就日益增加的安全用冰工程设计所需冰表面温度取值也给予定量讨论;对气候变化下的冰内和冰下水体生态适应问题所需的冰面温度日内变化速率和开河期冰凌爆破所需冰表面温度的取值也进行探索。尽管受国际气象资料观测规定的限制,历史资料的应用存在利用接近观测时刻资料的事实,但仍然期望这些分析和讨论能够推动科学地、更广阔地应用冰表面温度。     

输水渠道冰盖增厚物理模型试验相似律研究

随着南水北调中线工程冰期输水相关问题研究的深入,理论研究成果亟需物理模型试验和原型观测数据的支持和验证,由于原型观测难度较大,且影响因素不可控,物理模型试验方法成为解决冰水力学问题的有效途径。现在国内外学者开展冰水力学模型试验的成果基础上,结合冰水力学理论研究成果,对以冻结模型冰为试验材料的输水渠道冰盖增厚物理模型试验相似律展开研究,并通过物理模型试验进行了验证。研究表明:冰凌下潜临界流速的比尺为λ0.5,水力加厚冰盖沉积厚度的比尺为λ,均遵循重力相似准则;对于力学加厚冰盖,由于冰凌黏结力不遵循重力相似准则,结冰期需设法控制黏结力;融冰期可按照重力相似准则设计,但需控制环境温度在结冰点以上,以减小冰凌间的黏结力;因此输水渠道冰盖增厚物理模型试验宜采用冻结模型冰为试验对象,试验应按照重力相似准则进行设计。     

寒冷地区供水工程引水明渠结冰问题数值模拟

以宁夏吴忠金积供水工程为例,对在冬季寒冷地区利用引水明渠从河流或水库引水时遇到的结冰问题进行研究。利用一维非恒定水力热力耦合数学模型对3种典型工况下引水明渠水温分布进行数值模拟,得出不同水深、不同风速时的初始结冰位置。利用冰盖厚度发展数学模型对10 a来冰盖发展情况进行数值模拟,并与经验公式计算结果进行对比,得到了较为一致的结果。根据数值模拟结果,得出寒冷地区引水明渠冬季供水时渠水温度的分布规律,总结出影响水温分布及初始结冰位置的因素。     

Comprehensive two-dimensional river ice model based on boundary-fitted coordinate transformation method简

River ice is a natural phenomenon in cold regions, influenced by meteorology, geomorphology, and hydraulic conditions. River ice processes involve complex interactions between hydrodynamic, mechanical, and thermal processes, and they are also influenced by weather and hydrologic conditions. Because natural rivers are serpentine, with bends, narrows, and straight reaches, the commonly-used one-dimensional river ice models and two-dimensional models based on the rectangular Cartesian coordinates are incapable of simulating the physical phenomena accurately. In order to accurately simulate the complicated river geometry and overcome the difficulties of numerical simulation resulting from both complex boundaries and differences between length and width scales, a two-dimensional river ice numerical model based on a boundary-fitted coordinate transformation method was developed. The presented model considers the influence of the frazil ice accumulation under ice cover and the shape of the leading edge of ice cover during the freezing process. The model is capable of determining the velocity field, the distribution of water temperature, the concentration distribution of frazil ice, the transport of floating ice, the progression, stability, and thawing of ice cover, and the transport, accumulation, and erosion of ice under ice cover. A MacCormack scheme was used to solve the equations numerically. The model was validated with field observations from the Hequ Reach of the Yellow River. Comparison of simulation results with field data indicates that the model is capable of simulating the river ice process with high accuracy.     

太阳辐射和地温对冰盖下水温的影响

太阳辐射可以透射穿过雪盖和冰盖与地温一起影响冰下水温的变化,加剧冰盖底部的融解和冲蚀,使得冰盖更易于崩溃开河。基于现有理论和原型观测研究成果,建立了描述太阳辐射在雪盖、冰盖和水体中的透射和吸收规律的数学模型;利用观测数据回归分析的方法,提出了太阳辐射可见光在水体中消光系数的参数化模型;然后研究了冰下水温的变化与太阳辐射和地温的函数关系。研究证实,冰下水温随太阳净辐射和地温的增加而升高,随雪厚和冰厚的增加而下降,并且与水体与冰盖的热交换系数成反比。此外,太阳辐射的透射可能使得开河期冰盖糙率不是减小,而是增大。     

用气温和冰厚修正黄河冰内雷达波速的物理机理和参数化

黄河平封冰和立封冰中冰晶体间以水膜形式存在有未冻结的自由水和非自由水,其含量随冰温变化。理论上冰内雷达波速取决于冰体自身的晶体结构和组分,但冰内未冻水含量可对其产生明显的影响;冰内未冻水含量取决于冰温,冰温又受控于气温、辐射和冰厚。分析了黄河什四份子2020—2021年冬季气温和雷达探测冰厚数据,发现气温主导的未冻水含量变化是影响雷达准确探测平封冰厚度的首要因子。通过确定黄河冰-水界面热通量,并引入含有气温、辐射、风速、云量的一维冰热力学模型,结合13个钻孔实测冰厚,计算了与雷达探测冰厚时刻一致的1251个热力学模拟冰厚。在此基础上,分别获得了气温升高过程和降低过程中粒状冰、柱状冰内雷达波速受气温影响以及受气温和冰厚联合影响的统计关系。最终确定将气温和冰厚对雷达波速联合影响的统计关系作为平封冰雷达波速动态修正的参数化方案,依此将固定式雷达冰内雷达波速由常数更换为函数,从而提高了平封冰雷达冰厚探测的精度。根据黄河存在非冻结冰花和堆积碎冰块,建议开展不同类型冰厚探测研究。     

封冻期冰塞堆积演变的试验研究

冬季北方河流中经常出现冰塞现象,极易诱发凌洪灾害。冰塞厚度是冰情预测工作的重要组成内容,不同冰塞演变过程中的冰厚研究成果尚不完善。借助水槽试验,通过改变水流与冰流量条件,对冰塞的堆积演变过程进行了试验研究。结果表明:冰塞堆积演变存在两种不同的顺序,不同的顺序对应不同的厚度变化过程,形成的冰塞分别是以水力增厚为主和以力学增厚为主。这一研究发现可为冰厚计算公式的选取提供有效的技术支撑。     

寒区抽水蓄能电站冰冻库容设计方法探讨

基于二重积分定义给出了抽水蓄能电站冰冻库容计算公式,其中的冰厚计算在分析水库冰情影响因素的基础上,考虑电站运行的影响,采用多元回归方法得到了我国北方寒区抽水蓄能电站最大冰厚计算方法.在总结我国北方已建抽水蓄能电站水库冰情分布特性的基础上,采用离散化方法将库面结冰区域分为厚冰区和薄冰区,提出一种实用的冰冻库容设计计算方法...     

考虑冰盖生消和冰-结构-冻土协同作用的渠道弹性地基梁模型

冰-冻破坏是寒区冬季输水渠道结构破坏的主要原因,而目前尚缺乏准确的分析方法和评价准则。本文从冰盖生消过程中结冰初期、流冰期和封冻期3个阶段衬砌结构冰冻破坏机理出发,考虑在冰-结构-冻土协同作用下,基于弹性地基梁Winkler理论推导了衬砌结构的挠曲线微分方程,分别建立了3个阶段衬砌结构的冰冻破坏力学模型,并结合相应荷载组合和边界条件对模型求解获得了衬砌结构的挠度、内力和应力的解析表达。应用该模型对南水北调京石段某输水渠道进行冰冻破坏分析计算,结果表明:结冰初期、流冰期和封冻期3个阶段衬砌结构的法向冻胀位移最大值分别为10.62、13.89和5.05 cm,对应3个阶段衬砌结构的截面最大拉应力分别为3.63、 4.11和2.05 MPa,且破坏位置均在冻结区坡板的中下部,与现场监测渠道冰冻破坏分布规律吻合。据此,建议寒区冬季输水渠道控制运用中应尽量缩短结冰初期、流冰期时间,延长第3阶段稳定封冻期时间,同时应合理控制地下水位和冰盖厚度。研究结果可为寒区冬季输水渠道抗冰冻设计提供理论依据和分析方法。     

伊丹河输水河道封冻期冰情演变数值模拟

根据水动力学、热力学、河冰水力学及固体力学等基本理论,针对吉林省伊丹河输水河段具体特征,建立了伊丹河的河冰数值模型,并应用1958—1988共30年的水文、气象资料对该输水河段进行了数值模拟及分析。结果表明,伊丹河输水河段冰期封冻形式为平封,可形成稳定冰盖从而实现冰期冰盖下输水,且满足冰期正常输水的要求。     

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。     

Thermal variability and stream flow permanency in an alpine river system

Despite the importance of thermal conditions in influencing biodiversity of alpine river systems, knowledge of year round stream temperature variability is very limited. This paper advances understanding of alpine stream temperature dynamics using hourly resolution data collected over two consecutive years at five sites within a glacierized basin in the French Pyrénées. The potential utility of temperature for understanding river flow patterns at ungauged sites (most notably during winter) is explored. The results indicated marked heterogeneity in water column temperatures; groundwater streams were typically warmer and more thermally stable than those draining snow and ice. Based upon stream temperature patterns, it appears possible to differentiate between river flow conditions including: free‐flowing, surface freezing, dewatering and snow cover. Notably, groundwater‐fed streams appeared to exhibit greater flow permanency than meltwater‐fed streams, the latter freezing for extended periods. These new insights into long‐term alpine stream thermal conditions have major implications for understanding the strategies adopted by benthic macroinvertebrate taxa when overwintering, particularly where streams freeze. Copyright © 2006 John Wiley & Sons, Ltd.     

Modelling Ice Dissipation in Eastern Lake Erie

A previously developed mathematical model, which considered both the heat exchange processes at the air-ice interface and the ice transport rate via the Niagara River Was used to simulate the ice dissipation process in eastern Lake Erie. The model, which assumed the ice thickness to be constant over the lake, has been further developed to take into account variable ice thickness. Buffalo meteorological data were used for the computation of the net heat exchange at the air-ice interface. Results of the model application illustrate the relative importance ofin-lake ice melt to ice transport via the Niagara River during the dissipation period. Model results were found to give reasonably good agreement with the limited ice information available for the 1976 dissipation period.     

Integrated simulation of runoff and groundwater in forest wetland watersheds

A Distributed Forest Wetland Hydrologic Model （DFWHM） was constructed and used to examine water dynamics in the different climates of three different watersheds （a cold region, a sub-tropic region, and a large-scale watershed）. A phenological index was used to represent the seasonal and species changes of the tree canopy while processes of snow packing, soil freezing, and snow and ice thawing were also included in the simulation. In the cold region, the simulated fall of the groundwater level in winter due to soil f~eezing and rise in spring due to snow and ice melting compare well with the observed data. Because the evapotranspiration and interaction of surface water and groundwater are included in the model, the modeled seasonal trend of the groundwater level in the sub-tropic region is in agreement with observations. The comparison between modeled and observed hydrographs indicates that the simulations in the large-scale watershed managed to capture the water dynamics in unsaturated and saturatedzones.