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Browsing by Author "Huang, Yen-Chen"

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    A computer method based on simulated annealing to identify aquifer parameters using pumping-test data
    (2008-02-25)
    Huang, Yen-Chen
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    Yeh, Hund-Der
    ;
    Lin, Yu-Chung
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    環境工程研究所
    ;
    Institute of Environmental Engineering
    Conventional graphical or computer methods for identifying aquifer parameters have their own inevitable limitations. This paper proposes a computer method based on a drawdown model and a heuristic approach of simulated annealing (SA) to determine the best-fit aquifer parameters of the confined and unconfined aquifer systems. The drawdown model for the confined aquifer is the Theis solution and the unconfined aquifer is the Neuman solution. The estimated results of proposed method have better accuracy than those of the graphical methods and agree well with those of the computer methods based on the extended Kalman filter and Newton's method. Finally, the sensitivity analyses for the control parameters of SA indicate that the proposed method is very robust and stable in parameter identification procedures. Copyright (c) 2007 John Wiley & Sons, Ltd.
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    An Optimization Approach to Leak Detection in Pipe Networks Using Simulated Annealing
    (2015-09-01)
    Huang, Yen-Chen
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    Lin, Chao-Chin
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    Yeh, Hund-Der
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    環境工程研究所
    ;
    Institute of Environmental Engineering
    A numerical approach, named as leak detection simulated annealing (LDSA), is developed based on the combination of transient flow simulations and simulated annealing to detect leaks in a pipe network. In the LDSA framework, an analysis model for pipe networks is first used to determine the steady-state nodal head solution of the network. For detecting the leaks, a valve closing suddenly at downstream side of the network is designed to create a transient event and then the method of characteristic is applied to simulate the transient flow in the network. Results from an experiment on leak detection in a single pipeline presented in the literature are used to verify the capability of LDSA in identifying the leaks. The result shows that the leaks represented by orifices in two cases can be accurately detected. The effect of C (d) A (discharge coefficient times effective area of orifice) on the detection is evaluated. In addition, three scenarios with three cases in each scenario are designed to test the performance of LDSA in numerical experimental studies for a synthetic network. For a very small value of C (d) A, it is found that the use of multiple observation points can increase the detection capability.
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    Analysis of pumping test data for determining unconfined-aquifer parameters: Composite analysis or not?
    (2009-07-01)
    Yeh, Hund-Der
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    Huang, Yen-Chen
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    環境工程研究所
    ;
    Institute of Environmental Engineering
    Recently, composite analysis (CA), which simultaneously analyzes all drawdown data from multiple observation wells, has been applied to determine the hydraulic parameters of an unconfined aquifer. Moench (1994) claimed that the value of specific yield (S (y)) determined from non-composite analysis (nonCA) is sometimes unrealistically low as compared with that obtained by water-balance calculation, and results from CA are better representative of aquifer properties than those from nonCA. To examine the validity of this assertion, the drawdown data from a pumping test conducted at Cape Cod, Massachusetts, USA, were analyzed using both nonCA and CA methods. The results show that the mean estimates of hydraulic conductivity and S (y) determined from CA are close to those determined from nonCA. In some cases the analysis based on CA also results in low estimates of S (y) as compared with those determined based on nonCA. A hypothetical case study is presented, which examines the effect of measurement errors on the estimated parameters. The results indicate that the CA method also gives poorer estimates of S (y) than the nonCA method if the pumping test data contain measurement errors. Moench AF (1994) Specific yield as determined by type-curve analysis of aquifer-test data. Ground Water, 32(6):949-957.
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    Analysis of pumping test data for determining unconfined-aquifer parameters: Composite analysis or not? (vol 17, pg 1133, 2009)
    (2010-12-01)
    Yeh, Hund-Der
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    Huang, Yen-Chen
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    環境工程研究所
    ;
    Institute of Environmental Engineering
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    Analysis of pumping test data for determining unconfined-aquifer parameters: Composite analysis or not? (vol 17, pg 1133, 2009)
    (2010-12-01)
    Yeh, Hund-Der
    ;
    Huang, Yen-Chen
    ;
    環境工程研究所
    ;
    Institute of Environmental Engineering
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    Determination of the parameter pattern and values for a one-dimensional multi-zone unconfined aquifer
    (2008-03-01)
    Chang, Ya-Chi
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    Yeh, Hund-Der
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    Huang, Yen-Chen
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    環境工程研究所
    ;
    Institute of Environmental Engineering
    In an aquifer, heterogeneity plays an important role in governing groundwater flow. Hence, aquifer characterization should involve both the pattern and values of the hydrogeological parameters. A new analytical solution describing the one-dimensional groundwater flow in a multi-zone unconfined aquifer is presented, and a methodology developed from the analytical solution and a heuristic approach for determining the pattern and values of the aquifer parameters are proposed. The analytical solution demonstrates that the hydraulic head varies spatially and is influenced by aquifer heterogeneity. Simulated annealing, a heuristic approach, is incorporated with the solution to simultaneously identify the pattern and values of the hydraulic conductivity for a horizontal multi-zone unconfined aquifer. This approach may be used to give an approximate result for a two-dimensional problem by dividing the model area into a number of transects along the transverse direction, identifying the parameter values along the longitudinal direction for each transect, and then smoothing the identified results.
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    Parameter identification for leaky aquifers using global optimization methods
    (2007-03-30)
    Yeh, Hund-Der
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    Lin, Yu-Chung
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    Huang, Yen-Chen
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    環境工程研究所
    ;
    Institute of Environmental Engineering
    In the past, graphical or computer methods were usually employed to determine the aquifer parameters of the observed data obtained from field pumping tests. Since we employed the computer methods to determine the aquifer parameters, an analytical aquifer model was required to estimate the predicted drawdown. Following this, the gradient-type approach was used to solve the nonlinear least-squares equations to obtain the aquifer parameters. This paper proposes a novel approach based on a drawdown model and a global optimization method of simulated annealing (SA) or a genetic algorithm (GA) to determine the best-fit aquifer parameters for leaky aquifer systems. The aquifer parameters obtained from SA and the GA almost agree with those obtained from the extended Kalman filter and gradient-type method. Moreover, all results indicate that the SA and GA are robust and yield consistent results when dealing with the parameter identification problems. Copyright (c) 2006 John Wiley & Sons, Ltd.
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    The use of sensitivity analysis in on-line aquifer parameter estimation
    (2007-03-15)
    Huang, Yen-Chen
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    Yeh, Hund-Der
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    環境工程研究所
    ;
    Institute of Environmental Engineering
    Generally, a pumping test requires a lot of effort and expense to perform the test and the drawdown is measured and analyzed for determining the aquifer parameters. The estimated aquifer parameters obtained from graphical approaches may not be in good accuracy if the pumping time is too short to give a good visual fit to the type curve. Yet, the problems of tong pumping time and required efforts can be significantly reduced if the drawdown data are measured and the parameters are simultaneously estimated on-Line. However, the drawdown behavior of the Leaky and unconfined aquifers in response to the pumping may have a time tag and the time to terminate the estimation may not be easily and quickly to decide when applying a parameter estimation model (PEM) on-Line to analyze the parameters. This study uses the sensitivity analysis to explore the influence period of each aquifer parameter to the pumping drawdown and the influence period is used as a guide in terminating the estimation when applying the PEM for on-line parameter identification. In addition, the sensitivity analysis is also used to study the effects of different value of S-y and the distance between pumping well and observation well on the influence time of S-y during the pumping. (c) 2006 Elsevier B.V. All rights reserved.