Ice-Tank and Numerical Study of Frazil Ingestion by Submerged Intakes

This paper addresses the problem of frazil ingestion by submerged water intakes located offshore in frigid water. It is well known that intakes under such conditions are prone to blockage by frazil, small ice crystals that commonly occur when water, agitated by wind or current, supercools. However, little quantitative information exists delineating how intake shape and size influence intake ingestion of frazil ice. Presented herein are insights and quantitative trends associated with those influences. The insights and trends were obtained from observations of frazil in a set of unique ice-tank experiments of a common intake configuration. The experiments were extended through numerical simulation. The essential intake layout considered herein comprises a conical inlet connected by pipe to an onshore pump station, and fitted with an elevated cap. The study’s findings show how either a cap or larger intake-rim diameter reduce the rate of frazil ingestion. Reducing the rate of frazil ingestion may enable an intake to operate longer during periods of water supercooling, and thereby reduce the possibility of blockage by frazil.     

Frazil Ice Blockage of Water Intakes in the Great Lakes

Each winter, municipal water supply and thermal power plants drawing water from the Great Lakes face the problem of their water intakes becoming blocked by frazil ice formed in the lakes. Little is known about the manner in which frazil forms, how it is drawn down to the depths at which the intakes are located, and how to prevent frazil from fully blocking intakes. This paper presents an overview of frazil formation and intake blockage in the Great Lakes. The paper first reviews the current understanding of the processes of frazil formation and intake blockage, and it adds new insight regarding the processes. It then describes the problem by way of case-study examples of frazil blockage of two intakes in Lake Michigan. Based on the case studies, and experiences with other intakes in the Great Lakes, the paper outlines methods for monitoring and mitigating frazil blockage. Two options are recommended: monitoring rate of water level drop in the pump forebay onshore from the intake, and rate of headloss increase between the intake and the forebay. Laboratory modeling of intake blockage is then presented.     

Field Investigation of Frazil Jam Evolution: A Case Study

Using field measurements of frazil jams from 1982 to 1989 in the Hequ Reach of the Yellow River, this paper discusses both the mechanism of evolution of a frazil jam, and the associated variation in water level. The variation in water level depends not only on the thickness of the frazil jam but also on the ice discharge. An empirical power-law relationship between the dimensionless ice thickness and Froude number is established. It has been found that the critical Froude number (under an ice cover condition) describing the transition from an ice jam to a hanging dam (overloaded ice jam) is about 0.075, with a dimensionless ice thickness of about 0.4. Interestingly, the results from the St. Lawrence River show a similar tendency with similar limits.     

Monitoring River Ice Conditions Using Web-Based Cameras

It is necessary to monitor river ice conditions at many northern locations where river ice can pose a risk. Web cameras have been used to monitor real-time ice conditions at hydropower plants, navigation reaches, or locations of ice-related flooding. This study demonstrates how Web cameras can also be used to investigate river ice processes. Hourly images taken over three winters at the confluence of the Allegheny River and Oil Creek in Oil City, Pa. were analyzed. Each image was manually reviewed and classified according to surface ice conditions: stationary ice cover, frazil ice, brash ice, or open lead formation in an ice cover. The percentage of the channel width in the image covered by each ice condition was recorded. The time series of ice data are presented along with the concurrent hydrological and meteorological data. The Web cameras were operational during the 2000–2001, 2001–2002, and 2002–2003 winter seasons and provided an effective and relatively inexpensive means of monitoring and analyzing the river ice conditions.     

Laboratory Study of Anchor Ice Growth

A counterrotating flume housed in a cold room was used to study anchor ice growth. The rate of anchor ice growth was monitored and quantified over time using a digital image processing system. The laboratory experiments were conducted over Froude numbers ranging from 0.18 to 0.76 using air temperatures of ?15 and ?20°C. The data suggest that the rate of anchor ice growth and the density of the resulting anchor ice have a dependence on the Froude number. The rate of anchor ice growth is observed to be a maximum at a Froude number of approximately 0.27. The qualitatively observed density of the anchor ice increases with increasing Froude number. The release of anchor ice is related to the Reynolds number; anchor ice was released for Reynolds number less than approximately 42,000, but remains attached for larger Reynolds numbers.     

Numerical Simulation of Supercooling Process and Frazil Ice Evolution

A mathematical model to simulate the supercooling process and frazil ice evolution is developed from previous models. It incorporates improvements for the physical process of initial seeding, ice particle growth, secondary nucleation, flocculation/breakup, and gravitational removal. A variable Nusselt number related to the flow turbulence is used. It has been found that two calibrated parameters, initial seeding, and a parameter that limits the secondary nucleation are correlated to the turbulence intensity, which is useful for the practical application of the model developed in this paper. Furthermore sensitivity analysis is carried out for these two parameters. The simulations results show good agreements with experimental data.     

冷轧带钢表面自动监测系统的研究

介绍一种新的基于图像处理的冷轧带钢表面自动监测系统。该系统采用面阵ＣＣＤ摄像头来采集带钢表面的图像,并且配备两种不同的照明方式,以检测不同类型的缺陷。系统在硬件结构和软件流程上进行了特殊的设计,以保证能够对带钢表面进行实时在线监测。同时,讨论了系统中采用的图像处理和模式识别方面的一些有效算法。用实际的样本对该系统进行试验,结果表明：该系统能识别六种常见的表面缺陷,识别率接近９０％。     

Experimental Study of Ice Jam Formation Dynamics

Ice jams pose a significant threat to human safety and property and represent one of the most dynamic of river ice processes. A key limitation in the advancement of knowledge of ice jam formation is the lack of quantitative data describing these dynamics, which is essential also for validation of advanced computational models. In this study, an experimental investigation of ice jam formation under steady carrier discharge was undertaken. Thus, unsteady effects were entirely due to the ice jam formation process itself. Quantitative data describing the variation in discharge, ice jam thickness, water level variation, and ice cover progression provides unprecedented data describing the dynamics of ice jam formation. While the processes of ice jam formation are indeed dynamic, the results of this investigation suggest that the analysis of ice jams formed under steady carrier flow conditions may be adequately handled by the usual steady flow ice jam stability relationships. The applicability of the popularly applied wide jam theory approach to modeling ice jams is further supported by this investigation.     

Musical imagery: Generation of tones and chords.

Four experiments are reported that examine Ss' ability to form and use images of tones and chords. In Exps 1 and 3, Ss heard a cue tone or chord and formed an image of a tone or chord one whole step in pitch above the cue. This image was then compared to a probe tone or chord that was either the same as the image in pitch, different from the image in pitch and harmonically closely related, or different and harmonically distantly related. In Exp 3, a random-tone mask was used to control for possible contributions of the cue in echoic memory. In both experiments tone images were formed faster than chord images, a result consistent with the idea of structural complexity as a determinant of image formation time. Response times and accuracy rates were found to parallel results found in music perception studies, results consistent with the idea of shared mechanisms in the processing of musical images and percepts. Exps 2 and 4 were control experiments examining the possible influence of demand characteristics and Ss' knowledge. Findings rule out the possibility that demand characteristics and Ss' knowledge were solely responsible for the results of Exps 1 and 3 and support the role of imagery. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Review of Alluvial-channel Responses to River Ice

The extent to which alluvial channels respond to ice-cover formation, presence, and breakup is not well understood. Some responses are well known and observed, such as increased flow stage or localized scour beneath the toe of an ice jam. Other responses are known in concept, such as altered bedform geometry, but are not well documented. Some potential responses are barely recognized, such as channel-thalweg adjustment. Many responses are temporal, such as the channel readjusting itself once ice is gone. A few responses may have a more enduring impact, such as a meander-loop cutoff. Most responses have not been investigated rigorously. The responses affect the full gamut of relationships between flow discharge and stage, macroturbulence structures, sediment-transport and mixing processes, and alluvial-channel stability. Of importance are the relative scales of length and time associated with ice-cover formation, presence and breakup, and a channel’s facility to respond to ice. This paper reviews alluvial-channel responses to ice formation, and raises practical engineering issues stemming from them.     

Bohai Sea Ice Monitoring Using Satellite Images

Sea ice monitoring and forecasting in the Bohai Sea is an operational task of the National Research Center for Marine Forecasts (NRCMEF), China. An overview of current satellite image receiving and processing systems at NRCMEF in relation to the Bohai Sea ice monitoring, including the use of NOAA-AVHRR, GMS, SAR of ERS-1, Radarsat, and SeaWiFS data, is presented.     

Flexibility in scanning described images.

Two experiments investigated why past research has shown that described images lead to the typical increase in reaction time (RT) with increasing memory set size (m), but undescribed images do not. Experiment 1 used ms 6 through 8. A described image group showed a linear relation between m and RT up to a m of 6, and no increase in RT thereafter. A story group (which was asked to tell a brief story for words in a memory set) and a repetition group showed a linear relation between m and RT throughout the range of ms, whereas an image group showed no relation between m and RT. Experiment 2 essentially replicated the first experiment but manipulated memory strategy as a within subject variable. Similar results were found. The apparent change from "serial" to "parallel" processing by the described image groups in both studies reinforces the notion of flexibility in processing, particularly when multiple representations are formed or when multiple encoding strategies are used. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

In situ Sea Ice Experiments in McMurdo Sound: Cyclic Loading, Fracture, and Acoustic Emissions

The breakup of first-year sea ice plays an important role in the dynamics and thermodynamics of polar ice covers. A recent research program has studied the in situ mechanical properties of the annual ice in Antarctica to support the development of physically based models of the breakup process. As part of this effort, two field trips were conducted to McMurdo Sound, and the present paper describes the experimental work and presents selected results. The in situ experiments investigated the constitutive and fracture behavior of edge-notched, square plate specimens of first-year ice and involved a detailed characterization of the physical properties and thermal state of the ice. Acoustic emissions, which are generated by microcracking, were monitored in the crack tip vicinity and provide insight regarding the size of the process zone. The paper describes the physical properties and microstructure of the sheet, the cyclic-loading response, and the acoustic emissions activity from an extensive series of experiments conducted on one of the in situ specimens. Varying the cyclic-loading frequency and amplitude provided a means to examine rate effects on the anelastic and viscous components of strain and the extent of microcracking near the crack tip. The viscous deformation rate estimated from the experiments exhibited an increasing power-law exponent with values between one and three. Acoustic emissions monitoring indicated that microcracking occurred in a process zone near the crack tip, and the size of the process zone increased with decreasing cyclic loading frequency. Practical aspects of the experiments are considered, and the results are put into context with the overall modeling goals of the project.     

Index for Estimating Physical and Mechanical Parameters of Model Ice

A series of experiments on the physical and mechanical properties of ethanol model ice were conducted to determine the basis for quality control of fine grain model ice. The measured physical parameters of the model ice included the ethanol solution freezing point, air temperature profiles in an ice basin, ice temperature profiles, solution temperature profiles, unfrozen liquid in ice, and ice density. The measured mechanical parameters of the model ice were compressive strength, flexural strength, and characteristic length and strain modulus. Based on these measurements, the dominating factor influencing the physical and mechanical parameters of model ice is found to be the amount of unfrozen liquid in ice. Therefore, a new index of quality control for the physical and mechanical parameters of ice is developed. The statistical relationships of these measured physical and mechanical parameters with the new index are shown.     

基于LED光源的热轧带钢表面质量在线检测系统的开发与应用

针对热轧带钢表面缺陷检测需求,采用机器视觉技术自主开发了热轧带钢表面检测系统。该系统采用高速线阵CCD摄像机获取高质量的带钢图像,配以自主研发的超高亮度LED光源,解决了高温带钢成像中远距离均匀照明的问题。系统中采用高效的图像处理和目标识别算法,保证了实时处理图像并准确识别表面缺陷种类。上线8个多月的运行结果证明：系统具有良好的缺陷检出与分类准确率,兼具实时性和可靠性。     

长图记录的数字图象识别与拼接

本文提出了一种基于数字图象处理和模式识别技术的方法，用于对无数值显示的长图记录曲线的数据提取、自动识别、区分每日记载，并直接形成月报表输出。     

Unsteady Effluent Dispersion in a Round Jet Interacting with an Oscillating Cross-Flow

Dispersion of a vertical round jet issuing into an unsteady cross-flow is investigated by laboratory and numerical experiments. An experimental technique has previously been devised to simulate a sinusoidally oscillating cross-flow situation with a nonzero mean flow velocity. The parameters of the cross-flow can be selected with ease. With this experimental technique, 12 cross-flow situations with systematic varying flow parameters are produced. The dispersion pattern of a jet in each cross-flow situation is studied by phase-locked dye visualizations and the dilution level of jet effluent is estimated using image processing. It is found that in a cross-flow of a large unsteadiness parameter, the jet dispersion pattern is significantly different from that of the same jet in a steady cross-flow. The jet effluent is organized into successive large-scale effluent clouds which are connected on the inner side by a bent-over effluent fetch. Specially designed experiments using time-controlled dye ejection are performed to investigate the formation mechanism of the effluent structures. Computational fluid dynamics (CFD) studies are carried out to supplement the experimental concentration data. In addition, the CFD results help to support the formation mechanism of the effluent flow structures and to explore their dynamics. In the time-averaged sense, unsteadiness in the oscillating cross-flow leads to a two- to threefold increase in jet width. The reduction in time-averaged concentration level of jet effluent is not as dramatic because there still remains high concentration of effluent inside the effluent clouds.     

低冰粘附强度表面设计与制备研究进展

表面结冰给通讯、电力等工业领域带来巨大损失,电加热和喷洒乙二醇等主动除冰方法虽然在一定程度上可以解决上述问题,但在能源、人力、环境方面需付出较高代价。为解决这一问题,低成本、低能耗的被动式防/除冰表面被寄予厚望。防/除冰表面主要分为延长结冰时间的防冰表面和低冰粘附强度的除冰表面。由于实际工况的复杂性,除冰表面比防冰表面更具有可实现性。除冰表面主要与低表面能、界面滑动和裂纹产生相关,低冰粘附强度表面按实现机理可分为化学改性低表面能表面、润滑表面、界面滑动表面和裂纹源表面。本文对不同类型低冰粘附表面的低冰粘附强度产生的原因和表面的制备方法进行总结。同时,对冰粘附强度的测量标准进行了说明和讨论,以解释不同的测试方法对防/除冰性能测试结果造成的差异。      

Numerical Study of Ice Jam Dynamics in Upper Niagara River

A two-dimensional numerical model for the dynamics of surface ice transport and ice jam in rivers was developed and applied to the upper Niagara River. The model treats river ice dynamics as a two-layer system consisting of a layer of surface ice coupled with the underlying water flow. A Lagrangian discrete-parcel method was used to model the ice dynamics, and a finite-element method to model the hydrodynamics. These two components are coupled through the interaction at the interface between the ice layer and the flowing water. The model was validated using recorded data and observations of ice runs and ice jams. Subsequently, the model was used to evaluate possible measures for mitigating ice jams that adversely affect hydropower operations on the upper Niagara River.