Yazar "Ciftci, Emin" seçeneğine göre listele

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    An area matching process to estimate the hydraulic parameters using transient constant-head test data
    (IWA PUBLISHING, 2016) Sahin, A. Ufuk; Ciftci, Emin
    A new parameter estimation methodology was established for the interpretation of the transient constant-head test to identify the hydrogeological parameters of an aquifer. The proposed method, referred as the area matching process (AMP), is based on linking the field data to the theoretical type curve through a unique area computed above these curves bounded by a user specified integration interval. The proposed method removes the need of superimposition of theoretical type curves and field data collected during the test, which may lead to the unexpected errors in assessing aquifer parameters. The AMP approach was implemented for a number of synthetically generated hypothetical test data augmented with several random noise levels, which mimic the uncertainty in site measurement together with porous media heterogeneity, and to an actual field data set available in the literature. The estimation performance of the AMP method was also compared with the existing traditional and recently developed techniques. As demonstrated by the conducted test results, the accuracy, reliability, robustness and simplicity of the proposed technique provide significant flexibility in field applications.
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    Assessment of advective-dispersive contaminant transport in heterogeneous aquifers using a meshless method
    (SPRINGER, 2012) Ciftci, Emin; Avci, Cem B.; Borekci, Osman S.; Sahin, A. Ufuk
    Groundwater solute transport phenomena typically occur in water-bearing zones with heterogeneous solute dispersive characteristics and/or media hydraulic properties. A radial basis function collocation method (RBFCM)-based numerical method was developed in order to investigate the ability of RBFCM to accurately portray solute transport phenomena under heterogeneous conditions. Simulations were performed for 1-D and 2-D transport scenarios in which scale-dependent dispersivity fields were taken into consideration and compared with available analytical solutions. Different radial basis functions (RBFs) were employed for assessing the sensitivity of the present method on the selected RBFs. The simulation results were also compared with the results of MT3DMS which is a modular three-dimensional transport model with alternative solution schemes including the method of characteristics, the implicit central finite difference and the third order total variation diminishing finite volume. The proposed model was also used to simulate a real case condition where solute transport through a two-layer soil medium had been investigated experimentally. The results showed that RBFCM represented a powerful tool for predicting the solute transport occurrence under heterogeneous conditions with high accuracy.
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    An integration-based estimation approach for the determination of slug test parameters under various flow geometries
    (SPRINGER HEIDELBERG, 2016) Sahin, A. Ufuk; Ciftci, Emin
    A simple parameter estimation procedure, designated as integration-based estimation ( IBE), was introduced to determine the hydraulic properties of an aquifer using slug test models subjected to certain flow geometries such as radial and spherical flows. The basic idea behind the proposed IBE approach is to link an integration value at pre-defined normalized head levels for field data with that of a theoretical type curve. The IBE method removes the need for the implementation of the classical graphical matching process which would be ineffective to acquire aquifer parameters for non-ideal aquifer conditions. As the second aspect of this study, a new decision tool was suggested to determine the suitable slug test model to be utilized for the site data since diagnosing the flow character properly is of crucial importance for following a convenient analysis procedure. The estimation performance and limitation of the proposed IBE method were tested for several slug test scenarios including radial and spherical flow models with a number of synthetically generated data sets as well as a field application. Results reveal that the IBE together with the identification methodology not only is able to retrieve aquifer parameters as reliable as the existing techniques in the literature but also diagnoses the flow character precisely as demonstrated in this study.
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    Modelling coupled density-dependent flow and solute transport with the differential quadrature method
    (GEOLOGICAL SOCIETY KOREA, 2017) Ciftci, Emin
    The salt water intrusion phenomenon endangering the groundwater sources, particularly in coastal aquifers, is modeled by the coupled density-dependent flow and solute transport equations. This study focuses on the solution of these interdependent equations by means of the polynomial based Differential Quadrature Method (DQM). The Lagrange interpolation polynomials were selected as basis functions to obtain weighting coefficients for approximating the spatial derivatives and the 4-stage, 4th order Strong Stability Preserving linear Runge Kutta (SSP-RK) algorithm was employed as the time integrator. Two well-known benchmark cases; Henry and Elder problems were examined to test the accuracy and the reliability of the proposed numerical model. Apart from these theoretical benchmark problems, the numerical model was tested with real experimental data from a laboratory-scale study in the literature. The DQM model was observed to provide stable and highly precise results regarding the current semi-analytical and numerical solution schemes.
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    Modelling soil water movement under unsaturated conditions with the Modified Cubic B-Spline Differential Quadrature method
    (PAMUKKALE UNIV, 2018) Ciftci, Emin
    This study focuses on modelling moisture movement in the unsaturated soil zone with the use of the Modified Cubic B-Spline Differential Quadrature method. The numerical solution of the Richards Equation, which is commonly used in the field of hydrogeology for describing soil moisture movement, was investigated. The differential quadrature method was employed to evaluate the spatial derivatives of the equation variables, and the 4th order Runge-Kutta Method was used to march the solution in time. To verify the accuracy of the developed model, three test cases having different boundary conditions were taken into consideration. The retrieved results are seen to be in good agreement with the values provided by the analytical and other available numerical techniques. On account of its simplicity, efficiency and high accuracy, this method can be an appropriate option for the numerical solution of this type of problems.
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    A practical approach for the interpretation of flowing well tests
    (SPRINGER HEIDELBERG, 2018) Ciftci, Emin
    Flowing well test is one of the tools employed to identify transmissivity and storage coefficient of a confined aquifer where the potentiometric surface is located above the ground surface, so that the groundwater flows naturally from the well without pumping. During a flowing well test, constant hydraulic head is preserved at the well while the discharge from the well decreases with time and the temporal variation of discharge provides significant information about aquifer characteristics. In this study, a simple and straightforward approach is presented as an alternative to a number of graphical or error minimization-based techniques available in the literature for analyzing data from flowing well tests. The proposed method employs a polynomial regression equation to establish a link between observed discharge and the theoretical dimensionless discharge that is introduced in the analytical solution, so as to retrieve the aquifer parameters. The method is tested with a vast number of synthetically generated data sets as well as a real data set reported in the literature. Besides its simplicity, the present method is seen to produce highly accurate and reliable estimations.