广州市地铁一号线振动传播对环境影响的测定与分析

通过对广州地铁一号线沿线地上66个截面，地下10个截面的振动测试，对不同的隧道截面形状给出不同的地表面振动传播公式，公式表明地面振动Z振级由振源振动，地质条件，列车运行速度，轨道平面曲率半径及测点至隧道侧壁距离等因素决定。     

THE LODGING VELOCITY FOR EMERGENT AQUATIC PLANTS IN OPEN CHANNELS1

ABSTRACT: The growth of aquatic plants in open‐channels has many adverse environmental effects including, but not limited to, impeding the transport of water, hindering navigation, increasing flood elevations, increasing sediment deposition, and degrading water quality. Existing control strategies include physical removal and chemical treatment. Physical removal is only a temporary solution and chemical treatment is unacceptable if the water will be consumed by humans. The hydrodynamic method can wash out the encroached aquatic plants by keeping flow velocity higher than the critical velocity required to bend and rupture (lodge) their stems. This approach is a promising, physically‐based, efficient, economic, and permanent solution for this problem. However, the success of this approach requires the accurate prediction of the critical lodging velocity. This paper presents an analytic study of the lodging velocity for the submerged portion of aquatic plants of narrow leaved emergent stems that are wider at bottom than the top. Based on the principles of engineering materials and the theory of turbulent flow, a semi‐empirical formula is derived for the prediction of the critical lodging velocity. It indicates that the lodging of aquatic plants is controlled not only by flow conditions but also the geometric and mechanical characteristics of the plants. These analytic results provide a satisfactory explanation of the lodging phenomena observed in the field and are verified by the available experimental data.     

Intensification of treatment processes for oily wastewater: Theoretical foundations for calculating the hydrodynamic characteristics of tube coalescers

We present the results of theoretical studies of the pressure fluid flow fundamental characteristics in tube coalescers used in the treatment processes for oily wastewater. It is shown that three different regions of flow (wall sublayer, transition sublayer, and flow kernel), having their own hydrodynamic characteristics, are formed in a cross section of the tube coalescer. In the viscous wall sublayer (of thickness δ_*), viscous frictional forces exceed inertial forces (Re_δ* < 1), and “creeping flow” is observed. This region borders on the transition sublayer (of thickness δ_** = δ_*), in which inertial forces exceed viscous frictional forces (Re_δ** > 1). For both laminar and turbulent flow, distribution laws of local velocities and velocity gradients along the pipe radius are obtained in each of the three regions. In the flow kernel, the linear distribution law of velocity gradients gives a square distribution law of velocities for both types of flow, but for the turbulent flow, the correction coefficients A = β and B = 2β ? 1 must be introduced.     

WAVE INDUCED FLOW AND TRANSPORT IN SEDIMENT BEDS1

ABSTRACT: The fate of contaminants in large water bodies is highly influenced by the transfer of flow and solutes across the water sediment interface. In this paper, an analytical model is presented where flow in both sediment bed and open channel is coupled at the interface through a boundary layer occupying the upper part of the sediment bed. The presence of this layer allows not only the capture of the inertia effects through a drag term in the generalized Darcy's equation, but also the specification of different soil parameters for the two porous zones. The flow is advective and driven by wave action along the water surface. The resulting system is solved for the pressure and flux in each sediment layer. The generated transport velocity fields are linked to a random walk simulation that is used to examine the trajectories of solute particles. Comparison of these trajectories against experimental tracer tests suggests a pattern very similar to the one attributed to the presence of surface mounds. The results clearly show the significance of the boundary layer and the drag term for soil with high permeability and the impact of both the thickness of the boundary layer and the length of the gravity wave relative to the depth of the water channel on the transport and exchange across the interface. The paper also examines the sensitivity of the mass exchange to the permeability of the two porous zones.     

解析研究内部爆炸驱动金属圆筒的运动

从柱壳运动的控制方程出发，应用壳壁发生贯穿破裂的Taylor判据，给出了内部爆炸加载下金属圆筒壳壁的运动轨迹、平均破裂时间、破裂应变、半径及破片初速度的解析表达式。结果表明：计算结果与相关文献中的实验结果基本符合。     

Canopy slope effect on the performance of the solar chimney power plant

Solar chimney power plants constitute an impressive construction by its size and its output seems low for its dimensions. Although many works have been carried out on the subject, there is still much scientific and technical improvement to be done. In the present work, we consider the modeling of turbulent flow under the effect of natural convection within a solar chimney power plant (SCPP) by performing numerical simulation using the Saturne Code coupled with Syrthes code. The objective of the study is the analysis of the collector cover slope influence on the performance of the SCPP in two cases. In the first case, the storage system considered is composed solely of the ground under the collector. For the second case, the storage system is made, in addition to the ground, of a 10 cm thick tub filled with water, covering the entire surface of the collector. The concept of minimizing the entropy production is also studied with the objective of optimizing the geometric configuration as well as the effect of the collector cover slope on the efficiency of SCPP. The boundary conditions are defined according to the meteorological data for a typical day available on the site of Adrar, Algeria. The results allow us to focus on the storage system influence on the SCPP performance and the duration of its operation after sunset. This leads to the improvement of the global efficiency of the SCPP. Results show the positive impact of the extra storage media use and the configuration which improves the velocity at the chimney entrance.     

AQUIFER PARAMETERS FROM CONSTANT DRAWDOWN NONSTEADY-LEAKY TYPE CURVES1

ABSTRACT: A drain function and set of type curves were defined for the mathematical solution that represents one-dimensional flow under nonsteady conditions in a leaky aquifer for the constant drawdown boundary condition. A match point procedure was developed for determining the aquifer parameters transmissivity, storage coefficient, and leakance based on the drain function and type curves. Use of the procedure is illustrated by an example that utilizes simulated aquifer drawdowns and flowrate data. The drain function and type curves developed in this investigation include the effects of leakage for the constant drawdown boundary condition, which is not included in the existing drain function and type curve found in the literature. Thus, a new set of type curves was developed that can be used to analyze drawdowns for one-dimensional flow in a leaky aquifer with constant drawdown at a line sink. Applications would include flow to a canal or river, drainage of agricultural lands, and dewatering associated with strip mining operations.     

ADVANCES IN THE BOUNDARY INTEGRAL EQUATION METHOD IN SUBSURFACE FLOW1

ABSTRACT: This paper explores some of the advances of the boundary element method, as applied to ground-water problems, during the last five years. Although the method is still somewhat limited compared to solution by finite elements, the range of solutions has increased considerably. Diffusion and advection-diffusion solutions are done efficiently. These include the incorporation of inhomogeneity, anisotropy, and nonlinear diffusion. The difficult problem of stream-aquifer interaction is an important application as it is much easier to follow a free surface with its multiple configurations. The application must be able to cycle between ground-water connection and disconnection with the stream and include seepage surfaces. Flow in fractured media is a natural application where the flow in fractures can usually be treated without a computational exception in spite of extremely high aspect ratios. The case of seawater intrusion forms a type of free surface problem and thus is a case for which the method has special advantages. For these and other applications the boundary element method provides an inexpensive technique for calculation where the data preparation and setup time is minimal. In most of these cases, programs can and have been written on microcomputers.     

Evaluating Flow Diversion Impacts to Groundwater‐Dependent Riparian Vegetation with Flow Alteration and Groundwater Model Analysis

An approach for assessing the potential ecologic response of groundwater‐dependent riparian vegetation to flow alteration is developed, focusing on change to groundwater. Groundwater requirements for riparian vegetation are reviewed in conjunction with flow alteration statistics. Where flow alteration coincides with groundwater‐related vegetation sensitivities, scenarios are developed for groundwater simulation. Groundwater depths and recession rates in the riparian zone are simulated for baseline and altered stream hydrographs, with changes to river stage and width represented with a transient, flow‐dependent boundary condition. Potential flow diversion from the Upper Gila River in New Mexico is examined. Statistical flow alteration analysis, applying prospective diversions to a 76‐year record of daily flow, shows that flows in the winter‐spring months and within the high‐pulse to small flood range are subject to greatest potential change. Groundwater simulation scenarios are developed for these flow conditions in representative dry, near‐average, and wet years. Differences in groundwater elevations, generally less than 0.25 m during the flow alteration period, dissipate rapidly following cessation of diversion. Relating groundwater depth, recession rates and range of fluctuations to riparian vegetation needs, we find adverse ecological response is not expected from groundwater impacts for the flow alteration examined.     

A LUMPED APPROACH TO THE INVERSE PROBLEM IN GROUND WATER HYDROLOGY1

ABSTRACT: A solution procedure to solve the inverse problem in ground water, based on lumped approach, has been proposed. The method has the following advantages: 1) exact determination of the boundary conditions and the physical laws of flow through porous media is not required; 2) all errors of approximation in describing the boundary conditions, physical laws, and the aquifer properties are lumped into the surrogate parameters; and 3) the same mathematical model can be employed both in the identification process and in the subsequent management studies. The optimal values of the surrogate parameters are found by using a multidimensional unconstrained optimization code devised by Powell. The solution procedure and the convergence characteristics of the proposed algorithm have been illustrated by two hypothetical problems.     

MODIFICATION OF NEILL'S EQUATION FOR STORM‐TIDE DESIGN FLOW ANALYSIS1

ABSTRACT: Design of bridges spanning tidal estuaries or bays requires an estimate of peak tidal flow. One common approach to estimating these flows (Neill's method) uses a first‐order approximation of uniform water surface rise in the water body. For larger water bodies, the assumptions of this method are decreasingly valid. This study develops a simple modification that accounts for the spatial variability in the response of tidal waterways to storm surge flows. The peak tidal flow predicted by Neill's equation is compared to the peak flow determined by numerical simulation of estuaries with simple geometries, ranging from 1 to 25 km in length, using the U.S. Army Corps of Engineers one‐dimensional unsteady flow model, UNET. Results indicate that, under certain conditions, it may be appropriate to apply a correction factor to the peak discharge and peak velocity predicted by Neill's method. An algorithm, developed by nonlinear regression, is presented for computing correction factors based on estuary length, shape, mean depth, and storm‐tide characteristics. The results should permit the design of more reliable, cost‐effective structures by providing more realistic estimates of the potential for bridge scour in tidal waterways, especially when a full solution of the unsteady flow equations is impractical.     

Hydrology of Clay Settling Areas and Surrounding Landscapes in the Phosphate Mining District,Peninsular Florida1

Abstract: The objective of this study was to use applied and naturally occurring geochemical tracers to study the hydrology of clay settling areas (CSAs) and the hydrological connectivity between CSAs and surrounding hydrological landscapes. The study site is located on the Fort Meade Mine in Polk County, Florida. The CSA has a well‐developed, subangular‐blocky, clay‐rich surface layer with abundant desiccation cracks and other macropores, and a massive, clay‐rich sublayer that is saturated below ～1.0‐2.5 m. A bromide tracer was applied to study hydrological processes in the upper part of the CSA. Bromide infiltrated rapidly and perched on a massive, clay‐rich sublayer. Bromide concentrations decreased in the upper part of the profile without being transported vertically down through the lower part of the profile suggesting that bromide was lost to lateral rather than to vertical transport. Infiltration and lateral flow were rapid suggesting that preferential flow through desiccation cracks and other macropores likely dominates flow in the upper part of the CSA. Naturally occurring solute and stable isotope tracers were used to study the hydrological connectivity between the CSA and the surrounding hydrological landscape. Three‐end mass‐balance mixing model results indicate that shallow and/or deep CSA water can be found in all downgradient waters and must be as much as ～50% of some downgradient waters. Discharge from the CSA to the surrounding surface water‐bodies and surficial aquifer occurs laterally through the berms and/or vertically through the massive, clay‐rich sublayer. However, the precise flow paths from the CSA to the surrounding hydrological landscape are unclear and the fluxes remain unquantified, so the precise effects of CSAs on the hydrology of the surrounding hydrological landscape also remain unquantified.     

DYNAMIC FLUID LOSS DURING VISCOUS FLOW THROUGH A POROUS VERTICAL SLOT1

ABSTRACT. An experimental study of two-dimensional viscous flow through a vertical slot with one highly resistant porous wall was made. The fluid loss area of the porous wall was divided into five sections. The fluid loss rate for the various subareas was measured as a function of the bulk flow rate through the slot and the viscosity of the fluid. Static flow tests through the porous media were also conducted for each fluid viscosity. The results indicate that the experimental data can be correlated in terms of the difference between the static flow rate and the dynamic fluid loss rate as a function of the bulk Reynold's number and the bulk flow rate. Stream function profiles were determined for each experimental run to visualize flow through the length of the slot. An empirical correlation was developed between the superficial entrance width, δ, and the ratio of bulk Reynold's number to the Reynold's number based on flow through the porous wall.     

CASING AND LEAK DEPTHS,AND SOLUTE TRAVEL TIMES TO WELLS1

ABSTRACT: A mathematical solution based on porous media flow is developed for solute travel time to a well as affected by a leak around the upper part of the casing. Consider a well of radius 0.2 meters (m) penetrating, fully, a semiconfined aquifer of thickness 6 m with impermeable casing length of 4.5 m, and screened casing length 1.5 m. Around the upper 1.5 m of the impermeable casing length, there is a highly permeable region (a leak). The radius of influence of the well is 10 m. The porous flow medium has a hydraulic conductivity of 10 m/day and a porosity of 0.25. Between the water table and the water level in the well, there is a steady state pumped down head difference of 0.3 m. Solute travel time from a point at the bottom of the leak to the well is 2.33 days. If the leak is sealed (grouted), the travel time is 6.24 days. Examples of six different geometries are given. Laboratory studies verify the theory. The computations should be useful in the design and protection of water wells from solutes, such as from agriculture, industry, strip mines, or sanitary landfills.     

Streamflow,Sediment Transport,and Geomorphic Change during the 2011 Flood on the Missouri River Near Bismarck–Mandan,ND

Geomorphic change from extreme events in large managed rivers has implications for river management. A steady‐state, quasi‐three‐dimensional hydrodynamic model was applied to a 29‐km reach of the Missouri River using 2011 flood data. Model results for an extreme flow (500‐year recurrence interval [RI]) and an elevated managed flow (75‐year RI) were used to assess sediment mobility through examination of the spatial distribution of boundary or bed shear stress (τ_b) and longitudinal patterns of average τ_b, velocity, and kurtosis of τ_b. Kurtosis of τ_b was used as an indicator of planform channel complexity and can be applied to other river systems. From differences in longitudinal patterns of sediment mobility for the two flows we can infer: (1) under extreme flow, the channel behaves as a single‐thread channel controlled primarily by flow, which enhances the meander pattern; (2) under elevated managed flows, the channel behaves as multithread channel controlled by the interaction of flow with bed and channel topography, resulting in a more complex channel; and (3) for both flows, the model reach lacks a consistent pattern of deposition or erosion, which indicates migration of areas of erosion and deposition within the reach. Despite caveats and limitations, the analysis provides useful information about geomorphic change under extreme flow and potential implications for river management. Although a 500‐year RI is rare, extreme hydrologic events such as this are predicted to increase in frequency.     

A Power Law Model for River Flow Velocity in Iowa Basins

This study explores power law relationships to estimate water flow velocity as a function of discharge and drainage area across river networks. We test the model using empirical data from 214 United States (U.S.) Geological Survey gauging stations distributed over the state of Iowa in the U.S. The empirical data are the measurements of the mean cross‐sectional velocity and concurrent discharge. The data are used to estimate parameters for a state‐wide model and to test for spatial variability for 15 large river basins contained within the state. Spatial differences among the basins are small but some parameters significantly differ from the state‐wide model. Using individual station data, the authors also explore a simpler power law model that disregards dependence on the drainage area. Overall, the study shows that including drainage area improves the model. Our study provides parameter values that can be directly incorporated into a regional scale routing model, and provides a framework for developing flow velocity models for hydraulically similar rivers in the U.S. and the world.     

Hydrologic and atrazine simulation of the Cedar Creek Watershed using the SWAT model

One of the major factors contributing to surface water contamination in agricultural areas is the use of pesticides. The Soil and Water Assessment Tool (SWAT) is a hydrologic model capable of simulating the fate and transport of pesticides in an agricultural watershed. The SWAT model was used in this study to estimate stream flow and atrazine (2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine) losses to surface water in the Cedar Creek Watershed (CCW) within the St. Joseph River Basin in northeastern Indiana. Model calibration and validation periods consisted of five and two year periods, respectively. The National Agricultural Statistics Survey (NASS) 2001 land cover classification and the Soil Survey Geographic (SSURGO) database were used as model input data layers. Data from the St. Joseph River Watershed Initiative and the Soil and Water Conservation Districts of Allen, Dekalb, and Noble counties were used to represent agricultural practices in the watershed which included the type of crops grown, tillage practices, fertilizer, and pesticide application rates. Model results were evaluated based on efficiency coefficient values, standard statistical measures, and visual inspection of the measured and simulated hydrographs. The Nash and Sutcliffe model efficiency coefficients (E(NS)) for monthly and daily stream flow calibration and validation ranged from 0.51 to 0.66. The E(NS) values for atrazine calibration and validation ranged from 0.43 to 0.59. All E(NS) values were within the range of acceptable model performance standards. The results of this study indicate that the model is an effective tool in capturing the dynamics of stream flow and atrazine concentrations on a large-scale agricultural watershed in the midwestern USA.     

MANAGEMENT OF WATER QUALITY IN RELEASES FROM SOUTHWESTERN IMPOUNDMENTS1

ABSTRACT. The objective of this investigation was to determine the selectivity of withdrawal which is possible in southwestern reservoirs. Two stratified flow solutions were examined to test their applicability under field conditions. Although both appeared capable of accurate prediction of the outflow velocity profile, the Bohan-Grace solution, which required less input data, was utilized to predict the chemical constituents of single and simultaneous releases from several southwestern impoundments. Prediction of outflow water quality was within fifteen percent for southwestern reservoirs as shallow as fifty-five feet. The withdrawal layer thickness for the subject Texas impoundments included the entire hypolimnion or epilmnion depending on outlet location. The sensitivity of the velocity profile to seasonal changes, reservoir discharge rate and withdrawal port dimensions also is illustrated.     

Three-dimensional nickel ion transport through porous media using magnetic resonance imaging

The transport of Ni2+ ions in a column, filled with porous media, was observed in three dimensions and time by magnetic resonance imaging (MRI) in a clinical scanner. For porous media we used glass beads or quartz sand in a saturated continuous flow mode. The magnetic moment of Ni2+ decreased the T1 relaxation time of 1H in aqueous solution. This concentration-dependent effect was used by a fast low angle shot (FLASH) MRI sequence for imaging the concentration of the dissolved ions. Since Ni2+ behaves as a conservative tracer under the chosen conditions, the tracer motion was representative for the water flow in the porous medium. Currently, we can achieve an isotropic spatial resolution of 1.5 mm and a temporal resolution of 170 s. The transport observation gives direct access to hydraulic flow properties of the porous media. The fluid flow velocity field was calculated by a fronttracking method and the statistical properties of the velocities were investigated. We also compared the experimental data with the three-dimensional particle tracking model PARTRACE, which uses the experimental flow field as input.     

天柱山国内旅游市场空间结构分析与优化

从旅游客源和客流两方面分析了天柱山国内旅游市场的空间结构特征及其演化:2002年与1996年相比,天柱山国内旅游客源市场有扩散趋势,但仍呈较强的集中性,客源吸引半径小幅上升,呈明显的近程性;旅游客流在景区空间呈现多中心辐射扩散的分布点.在此基础上,划分了天柱山国内旅游市场空间圈层结构,对不同的圈层结构提出了不同的经营策略,以达到优化市场空间结构的目的.