2D Flow Box

While students are required to draw a flow net by hand and learn about flow and equipotential lines displayed on paper, a fully operational flow net box provides a significant learning model for the students. This flow net box was constructed using 0.5” thick acrylic sheets, and is 24” long by 18” tall by 12” deep. The bottom of the acrylic sheet pile wall that separates the head water from the tail water is approximately 8” from the bottom of the box. Compression fittings are installed at different elevations on each end of the flow net box to adjust the constant heads on each side of the sheet pile wall to induce flow through the sand as needed. A tiny amount of powder dye installed inside dry sand using filter paper at select points at the soil surface on the upstream side is utilized to create colored flow lines through the sand as 2D seepage occurs. The model is also used to review fundamental concepts needed to perform their calculations. For example, concepts including initial and final total hydraulic head, head loss, flow lines, and equipotential lines are defined directly on the model while a grease pencil is used to draw the equipotential lines directly on the front of the box. Subsequently, the instructor is able further demonstrate how to calculate elevation head, total hydraulic head, pressure head, and pore pressure at any point within the flow net medium.




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