A resistor-capacitor analog model for simulating a nonsteady-state, two dimensional groundwater flow through a homogenous isotropic and confined aqiufer under constant discharge condition

Date

1987

Abstract

A resistor-capacitor analog model is constructed to stimulate a nonsteady-state, two-dimensional groundwater flow in sixteen (16) idealized aquifers of different hydrologic geeometries and boundaries. The analog model consists of regular arrays of resistors and capacitors representing the transmissibility and storage coefficients of the aquifer system. The resistors are inversely proportional to the coefficients of transmissibility and vertical permeability of the aquifer. The capacitors store electrostatic charge in a manner analogous to the storage of water in the aquifer. Electric pulsating current introduced to the model by a function generator at the site of pumping well generated data on the voltage distributions at different nodes in the model. The data in the form of time-voltage graphs and recorded by the oscilloscope are analogous to the time-drawdown graphs for the real aquifer system. Verification of the model is done by comparing the data obtained from the analog model and from analytical solutions. The analytical solution is facilitated with the use of computer programs written in the Turbo Pascal language. The calculation of the drawdown distributions due to a pumped well in an aquifer with impervious or recharge boundaries is done with the application of the image-well theory. Close agreement of the drawdown contours determined from the analog model and from analytical solutions for the sixteen idealized aquifer situations obtained. The data generated by the analog model simulating aquifers bounded by recharging source(s) almost matched those obtained by analytical solutions except in the regions near the termination strips where drawdown values computed by the analog model are about 1.5 times more than the expected values. Comparison of drawdown contours for aquifers bounded by parallel impervious boundaries based on the analog and analytical solutions indicated close agreement only within an average of radius of 3,000 feet from the pumped well. Drawdown values near the impervious boundary and termination strips are larger than the expected values. The data generated by the analog model stimulating aquifers with impervious boundaries that are perpendicular to each other are smaller than the expected values. The drawdown values based on the analog model stimulating leaky aquifer of infinite areal extent closely matched those obtained by analytical method within a radius of 2,000 feet from the well. Beyond this distance, the analog model generated data significantly deviated from the expected values. This indicated inappropriate selection of the resistor values to stimulate the confining later of the leaky aquifer.

Document Type

Master Thesis

Language

English

LC Subject

Water, underground, Electromechanical analogies

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 995 1987 A2 L55

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