A Procedure for Calculating Groundwater Flow Lines.
COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER NH
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A methodology for the calculation of flow lines in steady or unsteady two-dimensional velocity fields is described. Although the principal application is intended to be determining fluid particle trajectories in groundwater flow, components of the methodology are relevant to more general problems of fluid flow. Two alternative numerical procedures from the core of the methodology. Each employs the method of characteristics to solve for the advection of fluid particles. The first uses an efficient, fourth-order Runge-Kutta, predictor-corrector algorithm based upon a constant time step. The second uses a fifth-order Runge-Kutta algorithm incorporating an embedded fourth-order result. This latter alternative includes automatic time-step modification and guarantees a prescribed level of accuracy. Several utility routines are provided in support of the method of characteristics. There is a two-dimensional spline calculation procedure for the analytic description of flow-field parameters, steady potential, and potential gradient. Spline interpolation subroutines enable the user to incorporate function and gradient evaluations directly into computer program code. There is also a routine for calculating average linear velocity for those flow situations where Darcys law is appropriate. A plotting routine features an option for producing flow-line map overlays to a user-supplied scale.
- Hydrology, Limnology and Potamology