Simple Method for Quick Estimation of Leaky-Aquifer Parameters

Simple method and explicit equations are proposed for estimating the parameters of leaky aquifers from drawdown at an observation well, which avoid the curve matching or initial estimate of the parameter. The proposed method is computationally simple and the calculations can be performed even on a handheld calculator. The application of the methods is illustrated, using published data sets. The new method yields quick and accurate estimates of the leaky-aquifer parameters, if observed drawdowns do not contain large errors. The proposed method can also analyze the early drawdowns for accurate characteristics/parameters of a confined aquifer, if the conductance of the aquitard is assigned a zero value. It is hoped that the proposed method would be of help to field engineers and practitioners.     

Parameter Estimation for Muskingum Models

A methodology for parameter estimation for the Muskingum model of streamflow routing is developed. The methodology minimizes the outflow prediction errors subject to the satisfaction of the streamflow-routing equations for all time stages in the routing process. The routing equations incorporate the Muskingum channel storage models. An algorithm is developed for parameter estimation that iteratively solves the governing equations to identify the Muskingum model parameters.     

Chance-Constrained Optimization-Based Parameter Estimation for Muskingum Models

The development of a chance-constrained optimization-based model for Muskingum model parameter estimation is presented. The desired Muskingum model parameters are to be useful to give the flood forecast in terms of expected flood for given limits of tolerance and probability of occurrence. When errors of observation occur, an error term is added to a mean flow to give the actual flow. The developed model minimizes the sum of squares of difference between the actual observed and computed outflows in order to determine the Muskingum model parameters. The constraints are the chance-constrained Muskingum flow routing equations. The first-order second moment method of chance-constrained optimization is used to develop the optimization model. The developed model is demonstrated for four scenarios of Muskingum model parameter estimation. The results show that, given the allowable limits of error in Muskingum model parameters, the developed model has a capability to give expected values of Muskingum model parameters when the historic data that are used for the parameter estimation process contain a specified amount of observation errors and obey a specified probability distribution. The chance-constrained optimization-based model for Muskingum model parameter estimation results into Muskingum model parameters that can give flood forecasts such that the forecasted flood allows the provision of better flood damage mitigation facilities.     

Parameter Estimation for Flow in Open-Channel Networks

Two mathematical models for parameter estimation in closed-loop, open-channel flow networks are presented. The parameter estimation models seek to determine the parameter values that would reproduce an observed flow profile in the channel network. The governing equations for gradually varied flow in channel networks are the optimization models’ constraints. The projected augmented Lagrangian method is used to solve the optimization models. Performance of these two optimization models is evaluated for a given closed-loop network configuration. Results establish the potential of the developed models for use in real-life flow scenarios.     

Biokinetic Parameter Estimation for ISB of PAH-Contaminated Soil

In situ bioremediation (ISB) has been shown to be an effective and cost-efficient method for remediating contaminated ground water and soil. One of the major disadvantages associated with this process is the lack of available kinetic information. The viability of respirometry to determine the relevant biokinetic parameters for degradation of contaminants in groundwater has been proven; however, little work has been done using soil systems. This work investigated the applicability of using respirometer data to determine the biokinetic parameters for soil systems. The specific soil investigated was contaminated with polycyclic aromatic hydrocarbons (PAHs), which contain 16 EPA priority pollutants. The work also investigated a logarithmic growth and modified Lineweaver-Burke approach for experimentally determining the maximum specific growth rate from batch degradation data. As expected, this research concluded that determining all biokinetic parameters from respirometer data was not a viable method for soil systems. Obtaining the maximum specific growth rate from batch degradation data provided more accurate results.     

Parameter Estimation for Multiple-Input Multiple-Output Modal Analysis of Large Structures

Experimental modal analysis (EMA) has been explored as a technology for condition assessment and damage identification of constructed structures. However, successful EMA applications such as damage detection to constructed systems pose certain difficulties. The properties of constructed systems are influenced by temperature changes as well as other natural influences such as movements in addition to any deterioration and damage. Writers were challenged in their attempts to measure the dynamic properties of an aged bridge by EMA due to inconsistencies within the data set due to short-term variations in ambient conditions. A complex interaction was observed between the dynamic properties of the bridge, hour-to-hour changes in temperature, and controlled damages applied to the bridge. Inconsistencies in the data set made curve fitting difficult for some common parameter estimation algorithms that have been designed to handle consistent data sets. Although the quality of measurements within the entire data set was affected by time variance and nonlinearity, increasing the number of reference measurements significantly improved the reliability of the information which could be extracted. In conjunction with the multiple-input multiple-output technique, a parameter estimation method using complex mode indicator function (CMIF) was developed and implemented in this study to determine the modal properties with proper scaling to obtain modal flexibility. This method proved to be very successful among many others with the data acquired from the aged and deteriorated highway bridge. In this paper, challenges in reliable identification of modal parameters from large structures are reviewed and the new CMIF based algorithm is documented. The method is evaluated on actual bridge data sets from a damage detection research study.     

Parameter Estimation for the Nonlinear Muskingum Model Using the BFGS Technique

In the past, various methods have been used to estimate the parameters in the nonlinear three-parameter Muskingum model to allow the model to more closely approximate a nonlinear relation compared to the original two-parameter Muskingum model. In this study, the Broyden–Fletcher–Goldfarb–Shanno (BFGS) technique, which searches the solution area based on mathematical gradients, is introduced. The technique found the best parameter values compared to previous results in terms of the sum of the square deviation between the observed and routed outflows, using the smallest number of computational iterations. A sensitivity analysis showed that the initial values of certain parameters were critical when finding the optimal solution. Although this gradient-based technique makes use of initial value assumptions and involves complicated calculus, different initial values reach the same optimal or near-optimal solution within less time. Moreover, this mathematical technique does not require the algorithm parameters that are essential factors in meta-heuristics such as genetic algorithm or harmony search. The technique also considers the hydrologic parameters to be continuous rather than discrete variables for pure structures.     

线性——倒数混料模型参数估计E最优正交区组设计

对含过程变量的三分含下界约束的线性—倒数混料模型 ,研究了参数估计的 E最优正交区组设计 ,并应用最优化理论给出了 ε0 =0 .5～ 3.5的最优典型设计点     

New Method for Estimation of Discharge

A new technique for drawing isovel patterns in an open or closed channel is presented. It is assumed that the velocity at each arbitrary point in the conduit is affected by the hydraulic characteristics of the boundary. While any velocity profile can be applied to the model, a power-law formula is used here. In addition to the isovels patterns, the energy and momentum correction factors (α and β), the ratio of mean to maximum velocity (V/umax), and the position of the maximum velocity are calculated. To examine the results obtained, the model was applied to a pipe with a circular cross section. A comparison between the profiles of the proposed model and the available power-law profile indicated that the two profiles were coincident with each other over the majority of the cross section. Furthermore, the predicted isovels were compared with velocity measurements in the main flow direction obtained along the centerline and lateral direction of a rectangular flume. The estimated discharge, based on measured points on the upper half of the flow depth away from the boundaries was within ±7% of the measured and much better in comparison to the prediction of one- and two-point methods. The prediction of the depth-averaged velocity values for the River Severn in the United Kingdom shows a good agreement with the measured data and the best analytical results obtained by the depth-averaged Navier–Stokes equations.     

Parameter Estimation of the Transient Storage Model for Stream–Subsurface Exchange

The transient storage model (TSM) is the most commonly used model for stream–subsurface exchange of solutes. The TSM provides a convenient, simplified representation of hyporheic exchange, but its lack of a true physical basis causes its parameters to be difficult to predict. However, the simple formulation makes the model a useful practical tool for many applications. This work compares the TSM with a physically based pumping model. This comparison is advantageous for two reasons: Advective pumping is known to be an important hyporheic exchange process in many streams, and the pumping model can be used to derive dimensionless transient storage parameters that are properly scaled with important physical stream parameters. Transient storage model parameters are shown to be dependent on both the timescale of observation and the shape of the breakthrough curve, i.e., on the temporal evolution of the solute concentration in the surface water. This indicates that the transient storage model can, in practice, lead to incorrect predictions when model parameters are obtained without consideration of the stream flow dynamics, the properties of the stream bed, or the process timescale. This work emphasizes the limitations of simplified models for hyporheic transport, and indicates that such models need to be carefully applied.     

On Parameter Estimation of Urban Storm-Water Runoff Model

An existing accumulation and wash-off model was applied and calibrated on a standard asphalt parking lot located in the northeastern United States. The field measured data consisted of rainfall, flow, and runoff samples taken from over 26 storm events monitored from 2004 to 2006. The contaminants under consideration include: total suspended solids, total petroleum hydrocarbons-diesel range hydrocarbons (TPH-D), dissolved inorganic nitrogen (DIN) (comprised of nitrate, nitrite, and ammonia), and zinc (Zn). The objective of the study was to provide probability distributions of model parameters for contaminants that have not been documented much (TPH-D, DIN, and Zn). The best fitting parameter values were found on a storm by storm basis. Subsequently, the range and variability of these parameters are provided for modeling purposes and other urban storm-water quality applications. A normal distribution was fitted to the optimized model parameter values to describe their distributions. A simulated annealing algorithm was used as the parameter optimization technique. Several examples are given to illustrate the methodology and the performance of the model. Finally, a Monte Carlo simulation was performed to assess the capability of the model to predict contaminant concentrations at the watershed’s outlet.     

Aquifer Parameter Estimation for a Constant-Flux Test Performed in a Radial Two-Zone Aquifer

A patchy aquifer or an aquifer with a finite thickness skin can be considered as a radial two-zone aquifer system, which can be characterized by five parameters, i.e., the thickness of the first zone and four aquifer parameters including the transmissivity and storage coefficient for each of the first and second zones. This paper proposes an approach based on an analytical solution of a constant-flux pumping in a confined two-zone aquifer and the simulated annealing algorithm to determine the five parameters simultaneously. The estimated results for the five parameters are fairly good even assuming the aquifer as a single-zone system at the beginning of the data analysis. The estimated results indicate that the first-zone parameters are much more difficult to accurately identify than the second-zone parameters due to insufficient early-time data and high correlation of the sensitivities among the first-zone parameters. However, the problem of inaccurate results obtained at the first-zone can be significantly improved if more densely temporal drawdown measurements are used.     

线性─对数混料模型参数估计D─最优区组设计

对含过程变量的三分量含下界约束的线性—对数混料模型，研究了参数估计的D—最优正交区组设计，并借助电子计算机给出了ε＝1％～10％的最优典型设计点．     

Parameter Estimation in Finite Element Simulations of Rayleigh Waves

Spectral analysis of surface waves measurements are used to develop subsurface soil profiles or as a tool to delineate abandoned crown pillar structures. Finite element modeling of Rayleigh waves has practical application in simulating SASW measurements. Developing a reliable and accurate finite element model to simulate Rayleigh waves requires the proper mesh dimensions and attenuation parameters. This research proposes a new simplified methodology for quantifying mesh dispersion effects. In addition, methods of verifying damping ratios for numerical simulations are presented. The evaluation of an array of nodal displacements in the frequency–wave-number domain effectively illustrates mesh dispersion effects and the presence of parasitic modes of vibration. Calculations of damping ratio show that mass and stiffness damping parameters are valid within a specified frequency bandwidth. The new techniques are tested for a half-space model; however, they can be used for the analysis of layered media. In addition, equations are given for the calculation of linear Rayleigh damping. These equations satisfy the conditions of an average damping with minimum variance within the frequency bandwidth of interest.     

Parameter Estimation in Groundwater Hydrology Using Artificial Neural Networks

The capability of artificial neural networks to act as universal function approximators has been traditionally used to model problems in which the relation between dependent and independent variables is poorly understood. In this paper, the capability of an artificial neural network to provide a data-driven approximation of the explicit relation between transmissivity and hydraulic head as described by the groundwater flow equation is demonstrated. Techniques are applied to determine the optimal number of nodes and training patterns needed for a neural network to approximate groundwater parameters for a simulated groundwater modeling case study. Furthermore, the paper explains how such an approximation can be used for the purpose of parameter estimation in groundwater hydrology.     

一种确定立方金属滑移系的简便方法

文中提供的方法是根据拉伸轴指数, 直接确定出立方金属的滑移系, 较一般图解方法简单、方便。     

Simple Curvilinear Method for Numerical Methods of Open Channels

Three-dimensional finite-difference or finite-volume models of sinuous open channels (e.g., narrow rivers, estuaries, and reservoirs) generally require boundary-fitted grids and curvilinear flow solution. Cartesian models with square grid cells are simpler to apply, but require a larger number of cells, as the cell size is determined by cross-stream resolution. This paper presents a simplified curvilinear approach suitable for systems where the along-stream length scale is larger than the cross-stream scale. The curvilinear Navier-Stokes equations are manipulated so the left-hand side is identical to the Cartesian momentum equations. The right-hand side then consists of grid-stretching curvature terms. These terms are written as functions of a perturbation parameter, so the first-order curvilinear effects are obtained with the lowest-order perturbation terms. As the Cartesian equations' form is preserved, we can readily adapt a Cartesian model to this perturbation curvilinear approach by adding the small curvilinear terms as explicit momentum sources.