INLET CONCENTRATION TIME NOMOGRAM FOR URBAN BASINS1

ABSTRACT: A physically-based nomogram to determine inlet concentration times for composite developed basins is presented. This nomogram is constructed from previously derived kinematic wave formulations of both catchment and gutter flow components of surface runoff. With specified physical properties of a basin and rainfall intensity-duration relationships, the inlet time can be obtained from the nomogram directly.     

A GIS‐ASSISTED DISTRIBUTED WATERSHED MODEL FOR SIMULATING FLOODING AND INUNDATION1

ABSTRACT: A distributed watershed model combining kinematic wave routing, 1‐D dynamic channel‐flow routing, and 2‐D diffusive overland‐flow routing has been developed to simulate flooding and inundation levels of large watersheds. The study watershed was linked to a GIS database and was divided into an upstream mountainous area and a downstream alluvial plain. A kinematic wave routing was adopted at the mountainous area to compute the discharge flowing into the alluvial plain. A 1‐D dynamic channel routing solving the St. Venant equations by the Preissmann method was performed for the main channel of the alluvial plain, whereas a 2‐D overland‐flow routing solving the diffusion wave equation with the Alternating Direction Explicit scheme was used for floodplains. The above two routings were connected by weir‐link discharge formula. The parameters in the model were calibrated and independently verified by single‐event storms. An example application of flooding/inundation analysis was conducted for the Taichung station and the Woozi depot (Taiwan High Speed Rail). Suggested inundation‐proofing measures ‐ including raising ground surface elevation of the station and depot and building a waterproofing exterior wall and their combination ‐ were investigated. It was concluded that building the waterproofing exterior wall had a strong tendency to decrease peak inundation depth.     

EFFECT OF RAINFALL-EXCESS DETERMINATION ON RUNOFF COMPUTATION1

ABSTRACT: Four methods of determining rainfall-excess are considered. They include Ø-index and equations of Horton, Kostyakov and Philip. These methods are utilized in a nonlinear kinematic wave model to predict surface runoff from two natural agricultural watersheds. The effect of determining rainfall-excess on surface runoff response is then examined. It is observed that errors in rainfall-excess constitute a major source of error in runoff prediction. The choice of a method of determining rainfall-excess is thus crucial to runoff computation.     

ESTIMATING PEAK RUNOFF FROM FIELD-SIZE WATERSHEDS1

ABSTRACT: A simple nonlinear runoff model was developed and tested for use on field-size agricultural watersheds. A Wooding idealization of the watershed topography was used. Kinematic wave equations were used with an assumed, instead of computed, overland flow, watersurface profile in order to simplify the numerical computations. The approach was used to synthesize runoff hydrographs for an agricultural watershed in Iowa. The accuracy of the synthesized hydro-graphs was judged by comparing the estimated and observed peak discharges and by comparing estimated and observed stages at the measuring weir. The mean errors were 0.01 in/hr and 0.05 ft, respectively. A qualitative comparison was also made with a detailed kinematic wave study. The largest variability occurred during the seedbed period for both models, which was attributed to changes in surface roughness. The roughness was more constant and the results more consistent for the canopy and ground residue periods.     

COMPUTATION OF STAGE-DISCHARGE RELATIONSHIPS AFFECTED BY UNSTEADY FLOW1

ABSTRACT: The dynamic relationship between stage and discharge which is unique to a particular flood for a selected station along the river can be determined via a mathematical model based on the complete one-dimensional equations of unsteady flow, i.e., the equations for the conservation of mass and momentum of the flood wave, and the Manning equation which accounts for energy losses. By assuming the bulk of the flood wave moves as a kinematic wave, the need for spatial resolution of the flood can be eliminated, and only the time variation of either the discharge or stage at the selected station is necessary for the computation of the other. The mathematical model can be used in river forecasting to convert the forecast discharge hydrograph into a stage hydrograph which properly reflects the unique dynamic stage-discharge relationship produced by the variable energy slope of the flood discharge. The model can be used also in stream gaging to convert a recorded stage hydrograph into a discharge hydrograph which properly accounts for the effects of unsteady flow. The model is applied to several observed floods at selected stations along the Lower Mississippi, Red, and Atchafalaya Rivers. The root mean square errors between observed and computed discharges are in the range of 3 to 7 percent, values well within the accuracy of the observations. A simple, easily-applied graphical procedure is also provided for estimating the magnitude of the effect of the unsteady flow on stage-discharge ratings. As a general rule, the dynamic effect may be significant if the channel bottom slope is less than 0.001 ft/ft (about 5 ft/mi) when the rate of change of stage is greater than about 0.10 ft/hr.     

ESTIMATION OF SURFACE WATER LAG TIME FROM THE KINEMATIC WAVE EQUATIONS1

ABSTRACT Numerous concepts of surface water lag time have been developed and applied in the past. In this report, hydraulic solutions of a lag time derived by Overton [1970] are presented for several idealistic surfaces using the kinematic wave equations. These surfaces are: (1) a uniform plane; (2) hillslope as a cascade of planes; (3) V-shaped watershed; (4) V-shaped watershed with hill-slopes; (5) converging surface; (6) concave surface. The lag times are shown to be related to roughness, length and catchment slope, and the input rate. These relations may be used immediately in predicting lag time as the parameter in a unit response function. A lag relation has been developed for a nonuniform catchment in terms of the lag of a uniform plane and a convergence factor. A numerical procedure is shown whereby the convergence factor can be evaluated for any nonuniform catchment from observed input and output data.     

Quantized control settings based tuning of a heaving wave energy converter in irregular seas

The increasing awareness of environmental issues attracts more attention on environmentally friendly energy sources. This leads to increasing research on effective use of renewable energy sources. Among them, wave energy offers a high potential. The wave energy converter systems used for transforming the wave energy into electrical energy have been a main research topic for decades. However, only a few of these systems has been successfully implemented. There seems to be some technical problems one of which is on their control applications. It has been reported that by means of appropriate control implementation, the performance of the wave energy converter system could be improved considerably. In literature, many different control techniques are reported. They appear to be weak due to implementation related restrictions. The present study proposes a novel control technique that is far more practical based on quantization of control settings. Various quantization levels and their effect on system power capture performance are studied. The technique assumes use of realistic off-the-shelf components with realistic features. The proposed method utilizes time-series-analysis technique with online parameter estimation feature. This new method does not require any knowledge of previous or future states of any of the system or sea state parameters, but only the currently available and measurable ones. The approach of the new control technique sets it apart from most of the previously reported ones. Therefore, the proposed technique is not only very much practical but also very much useful in improvement of the system power performance relative to passive techniques.     

Numerical modeling of diazinon transport through inter-row vegetative filter strips

A numerical simulation model of pesticide runoff through vegetative filer strips (PRVFS) was developed as a tool for investigating the effects of pesticide transport mechanisms on VFS design in dormant-sprayed orchard. The PRVFS model was developed applying existing theories such as kinematic wave theory and mixing zone theory for pesticide transport in the bare soil area. For VFS area, the model performs flow routing by simple mass accounting in sequential segments and the pesticide mass balance by considering pesticide washoff and adsorption processes on the leaf, vegetative litter, root zone and soil. Model sensitivity analysis indicated that pesticide transfer from surface soil to overland flow and pesticide washoff from the VFS were important mechanisms affecting diazinon transport. The VFS cover ratio and rainfall intensity can be important design parameters for controlling diazinon runoff using inter-row VFS in orchard. The PRVFS model was validated using micro-ecosystem simulation of diazinon transport for 0, 50 and 100% VFS cover conditions. The PRVFS model is shown to be a beneficial tool for evaluating and analyzing possible best management practices for controlling offsite runoff of dormant-sprayed diazinon in orchards during the rainy season.     

HYDROLOGIC MODELING OF A BIOINFILTRATION BEST MANAGEMENT PRACTICE1

ABSTRACT: The goal of this research was to develop a methodology for modeling a bioinfiltration best management practice (BMP) built in a dormitory area on the campus of Villanova University in Pennsylvania. The objectives were to quantify the behavior of the BMP through the different seasons and rainfall events; better understand the physical processes governing the system's behavior; and develop design criteria. The BMP was constructed in 2001 by excavating within an existing traffic island, backfilling with a sand/soil mixture, and planting with salt tolerant grasses and shrubs native to the Atlantic shore. It receives runoff from the asphalt (0.26 hectare) and turf (0.27 hectare) surfaces of the watershed. Monitoring supported by the hydrologic model shows that the facility infiltrates a significant fraction of the annual precipitation, substantially reducing the delivery of nonpoint source pollution and erosive surges downstream. A hydrologic model was developed using HEC‐HMS to represent the site and the BMP using Green‐Ampt and kinematic wave methods. Instruments allow comparison of the modeled and measured water budget parameters. The model, incorporating seasonally variable parameters, predicts the volumes infiltrated and bypassed by the BMP, confirming the applicability of the selected methods for the analysis of bioinfiltration BMPs.     

Road Erosion and Delivery Index (READI): A Model for Evaluating Unpaved Road Erosion and Stream Sediment Delivery

The Road Erosion and Delivery Index (READI) is a new geographic information system–based model to assess erosion and delivery of water and sediment from unpaved road networks to streams. READI quantifies the effectiveness of existing road surfacing and drain placements in reducing road sediment delivery and guides upgrades to optimize future reductions. Roads are draped on a digital elevation model and parsed into hydrologically distinct segments. Segments are further divided by engineered drainage structures. For each segment, a kinematic wave approximation generates runoff hydrographs for specified storms, with discharge directly to streams at road–stream crossings and onto overland‐flow plumes at other discharge points. Plumes are attenuated by soil infiltration, which limits their length, with delivery occurring if plumes intersect streams. Sediment production and sediment delivery can be calculated as a relative dimensionless index. READI predicts only a small proportion of new drains and new surfacing results in the majority of sediment delivery reductions. The model illustrates how the spatial relationships between road and stream networks, controlled by topography and network geometries, influence patterns of road–stream connectivity. READI was applied in seven northern California basins. The model was also applied in a recent burn area to examine how reduced hillslope infiltration can result in increased hydrologic connectivity and sediment delivery.     

CHANGES IN HYDROLOGIC RESPONSE DUE TO STREAM NETWORK EXTENSION VIA LAND DRAINAGE ACTIVITIES1

ABSTRACT: The objective of this work is to determine the effects of extension of a stream network through land drainage activities during the late 1800s on the hydrologic response of a watershed. The Mackinaw River Basin in Central Illinois was chosen as the focus and the pre‐land and post‐land drainage activity hydrologic responses were obtained through convolution of the hill slope and channel responses and compared. The hill slope response was computed using the kinematic wave model and the channel response was determined using the geomorphologic instantaneous unit hydrograph method. Our hypothesis was that the hydrologic response of the basin would exhibit the characteristic effects of settlement (i.e., increases in peak discharges and decreases in times to peak). This, indeed, is what occurred; however, the increase in peak discharges diminishes as scale increases, leaving only the decrease in times to peak. At larger scales, the dispersive effects of the longer hill slope lengths in the pre‐settlement scenario seem to balance the depressive effects of the longer path lengths in the post‐settlement scenario, thus the pre‐settlement and post‐settlement peak discharges are approximately equivalent. At small scales, the dispersion caused by the hill slope is larger in the pre‐settlement case; thus, the post‐settlement peak discharges are greater than the pre‐settlement.     

FLOOD ROUTING THROUGH A FLAT,COMPLEX FLOODPLAIN USING A ONE-DIMENSIONAL UNSTEADY FLOW COMPUTER PROGRAM1

ABSTRACT: The routing of flood waves through the Central Basin of the Passaic River in New Jersey is complex because of flat gradients and flow reversals. The one-dimensional unsteady flow program DWOPER, developed by the National Weather Service, was used to simulate flood wave movement through the Basin. A historical event was used for calibration and two synthetic events were simulated. Boundary conditions consisted of discharge hydrographs at inflow points to the study area, local flow hydrographs at interior points, and a stage discharge relation for flow over the crest of a diversion dam at the basin outlet. Manning's n values were adjusted based on stage and discharge data for the historical event; however, verification data were not available for events comparable in magnitude to the synthetic events. Aspects of the investigation reported include techniques for characterizing the flow system, model calibration, techniques for representing a tunnel diversion, and simulation results.     

Biodiesel synthesis and characterization using welted thistle plant (Carduus acanthoides) as source of new non-edible seed oil

In this work we applied base catalyzed transesterification to convert non-edible welted thistle oil (Carduus acanthoides) as new non-edible feedstock into biodiesel (Fatty acid methyl esters). The highest biodiesel yield of 88% was obtained using optimized reaction conditions of 70°C and 5:1 molar ratio (methanol:oil). The synthesized esters were characterize and confirmed by the application of NMR and FT-IR techniques. Gas chromatography and mass spectroscopy identified different fatty acids as palmatic acid (C16:0), oleic acid (C18:1), linoleic acid (18:2), arachidic acid (C20:0), eicosanic acid (C20:1), and erucic acid (C22:1) in the oil of welted thistle. Six corresponding methyl esters reported in welted thistle oil biodiesel includes 9-hexadecenoic acid, hexadecanoic acid, 9-octadecadienoic acid, 11-eicosanoic acid, eicosanoic acid and 13-docosenoicacid. Fuel properties, such as density @40°C Kg/L (0.8470), kinematic viscosity @ 40°C c St (4.37), flash point (95°C), cloud point (+4°C), pour point (?5°C), and sulfur contents (0.0112% wt) of the biodiesel produced were compatible with American Society for Testing and Materials D 6751 specifications.     

废轮胎多孔隙消波结构物特性之初期研究

基于废旧轮胎再利用及研发简易且低廉的施工方法与维护成本,本研究以规则波水工模型试验研究提出应用于港口码头的多孔隙弹性帷幕的初步理念。利用模型车轮胎以模块化方式组装成弹性帷幕后安装于码头前壁,研究多种周期波浪作用及不同消波室纵深对波浪反射率的影响。实验结果表明,简单的单一消波室多孔隙弹性帷幕对短周期波浪的消波效果较显著,消波室纵深较大者反射率较低,但可能引致水体振荡,后续可再强化消波室的消能效果。未来如能妥善研究废旧轮胎应用于多孔隙弹性帷幕消波结构物的施工与维修方法,除可缓解废旧轮胎处理给环境带来的压力外,也提供一种可用于简易渔港的施工简单、维修容易且资源再利用的消能结构物,该工程技术亦可输出至发展中国家,符合可持续发展观。     

碟形越浪式波能发电装置的三维数值模拟

基于计算流体力学软件的三维数值模拟技术,分析了碟形越浪式波能发电装置的越浪性能,通过构建基于水气两相VOF(Volume of Fluid)模型的三维数值波浪水槽对该装置进行三维数值模拟研究,数值计算结果与物理试验结果相互对比验证较为吻合,验证了所构建的三维数值波浪水槽的可靠性,通过考察装置的坡度、导流叶片个数、干舷高度对越浪性能的影响确定装置的最优结构参数。结果表明,在装置的斜坡面边缘增加回流板可减少波浪的反射,提高装置的越浪性能。在数值模拟中将装置的斜坡面边缘处安装回流板对碟形越浪式波能发电装置参数进行优化,通过分析回流板的长度对装置越浪性能的影响来探索最优回流板长度。     

Wave energy vs. other energy sources: A reassessment of the economics

The large scatter in the predictions of wave energy costs, which is caused in part by the simplifications assumed by existing models, is a hindrance for the development of this promising renewable. In this context, the main objective of this paper is to reassess the cost of wave energy taking into account a number of elements that are usually overlooked, or not considered simultaneously. This analysis has been performed in relation to the European context. The direct and indirect costs of a wave farm are examined, and a value for each is presented. The levelized cost (€/MWh) of wave energy is then calculated for different scenarios in order to compare the profitability of wave energy with that of other energy sources. After that, a sensitivity analysis is carried out to identify the main parameters affecting the total cost, considering in particular the effect on the levelized cost of considering: (i) the cost reductions arising from economies of scale and technological effects; (ii) an O&M cost variable throughout the useful life of the farm; and (iii) the externalities. In sum, this work sets the basis for a thorough economic comparison of wave energy with other sources of energy.     

KINEMATIC FLOW ON LONG IMPERMEABLE PLANES1

An analysis of more than 200 overland flow hydrographs generated by simulated rainfall on long impermeable planes showed that kinematic waves prevailed over dynamic waves. Although laminar flow appears to occur at low flows, most flows appear to be either in the transition from the laminar to the turbulent state or in a fully developed turbulent state. Location of the laminar-turbulent transition could not be explained in terms of Reynolds number alone. The transition was significantly affected by rainfall intensity-a factor which rendered quantification of the transition indeterminate. However, the error involved in treating all flows as turbulent would be small with the resulting analysis made considerably less complex.     

含硫化亚铁颗粒的乳化原油净化处理方法

采用超声波和离心法在室内进行了从被硫化亚铁颗粒污染的乳化原油中回收原油的试验,试验结果表明:超声波-离心-溶剂稀释-离心处理工艺中,超声波处理工序主要用于乳化原油中游离水和部分乳化水的脱除,以降低后续离心处理工序的负荷。用超声波-离心处理工序分离出的沉渣和油、水过渡层经溶剂稀释后进行第二次离心处理。两次离心处理中所得到的净化油混合可作为商品原油外输,第二次离心处理中分离出的沉渣和油、水过渡层经进一步除油后可作为固体废物处理。     

海上溢油下潜过程特征的实验考察

海上溢油行为的研究是预测其归宿、控制其危害的关键所在。由于目前对溢油下潜于水时所受多因素影响、经历多个子过程的综合效应不清,文章用挡板烧瓶模拟波浪,考察其行为特征。结果表明:波浪类型对下潜率影响最大,破碎波和规则波下油的下潜率差异可达79.8%;上浮过程的影响可使得下潜率随时间出现最大值,随分散剂含量的增加有最大值。对比静置中下潜率的变化规律,可认为波浪通过夹带和破碎作用使油下潜,分散剂则增加了下潜稳定性。实验结果可对海面溢油下潜过程的预测提供理论依据和实验数据。     

WIND GENERATED WAVES IN LAKE OKEECHOBEE1

ABSTRACT: The study of wind generated waves is important because waves affect sediment resuspension in lakes. Measurements of wind velocity and wave elevation were made at three different stations in Lake Okeechobee. Significant wave heights were computed using a direct count from the recorded data, and verified by the root-mean-square value approach. The correlation between wind stress and significant wave height also was analyzed. The data revealed a strong correlation. In addition to field measurements, a Boussinesq-type wind-wave model was developed to simulate wind-generated, long-propagating waves. This model included the effects of wind stress and bottom viscous dissipation. Wave elevation and velocity field were evaluated numerically. A six-day simulation using 1996 wind data was conducted. Simulated significant wave heights were found to agree reasonably well with measured values. A predictive wind-wave model provides information about wind generated waves, which is used to compute bottom shear stresses required for sediment resuspension studies.