Open channel flow misconceptions and ontological categories

Abstract

National calls have been made for the identification of preconceptions and misconceptions in science and engineering. Identifying misconceptions can provide a basis for improved research-based curriculum development and implementation. The recognition of false beliefs and flawed mental models of these concepts can also contribute to theories of conceptual change. The purpose of this research was to identify misconceptions related to open channel flow. During spring and fall of 2011, out of 91 students from two sections of `Water Resources Engineering' course, 50 students were interviewed, and 41 students were given a pre/post test. The goal of these open-ended interviews and pre/post-tests was to obtain detailed data on students understanding of open channel flow concepts. Results suggest students have misconceptions relating to the hydraulic and energy grade line (HGL/EGL), flow transitions, and flow profiles. Many students have the correct terms of the HGL and EGL but lack understanding of where the terms re on an open channel flow profile. A large percentage of tested students revealed false beliefs relating to transitions. For example, more than 50 percent of tested students drew a decrease in water depth for a subcritical drop, rather than an increase in depth. Students also had difficult in labeling subcritical, critical, and supercritical places along flow profiles and how water flows over or under different weir structures. Repairing these fundamental misconceptions is essential for students to be able to apply these concepts in diverse situations and learn more advanced topics.