SIMULATION OF GROUND WATER FLOW NETS USING CONDUCTIVE - PAPER ANALOGS: FURTHER WORK USING A NEW CONDUCTIVE TAPE METHOD

Flow nets used in the simulation of ground water flow involve (1) analog methods using conductive paper, (2) electrical resistance networks or (3) numerical simulation. Since there is general agreement that there is an analogy between electrical flow and ground water flow, the conductive paper analog method gives the student a "hands on" experiment in simulating ground water flow nets. Although "conductive paper analogs are limited to isotropic homogeneous systems in two dimensions" they "can handle complex shapes and complex boundary conditions" (Freeze and Cherry 1980). However, until now, most conductive paper analog methods employ "a conductive ink" of some kind to create the constant head boundaries on the conductive paper. These inks leave a conductive residue while some liquid evaporates. This new method employs SCOTCH 1181^® conductive tape in lieu of conductive ink. This conductive tape can be easily purchased commercially and is safer and to use than any conductive ink product. For instance, the label of the conductive ink that we previously used read "CAUTION" "Flammable"…"Avoid breathing of vapor"…"Harmful or fatal if swallowed"…."Avoid contact with skin and eyes"…finally "contains butyl acetate." Initially, this author began searching for a safer method of performing electrical field experiments in our introductory physics laboratories. After trying various other methods, the conductive tape method was found to work the best. The tape can be used for a multitude of electric fields because it is easily cut into circles or any other shape. Correspondingly, it can also be used to in the simulation of ground water flow nets. The student performs the simulation by connecting a 12-volt power supply to the conductive tapes fastened to the conductive paper. Equipotential lines are plotted on the conductive paper and the entire equipotential field is generated. The student can then investigate and discover the flow nets for various "irregular" configurations.