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Abstract Title: Students’ reasoning in fluid dynamics: Bernoulli’s principle vs. the continuity equation
Abstract: In this work we investigate students' thinking about and difficulties with incompressible, steady pipe flow by giving two fluid mechanics problems to undergraduate engineering students. We find that students have difficulty applying and prioritizing the two basic principles of mass conservation (continuity equation) and energy conservation (Bernoulli's equation) when distracted by questions which involve gravity, friction or pressure.

Instead of invoking the continuity equation, a considerable number of students based their answers on ill-supported assumptions about local pressures (i.e. Bernoulli-type: 'lower pressure means higher velocity' or descriptive-type: 'higher pressure leads to higher velocity'). Others based their reasoning on analogies to single-particle motion ('flow velocity decreases when flowing upwards or friction is present').

More generally, our data indicate that students have difficulties i.a. in realizing the meaning of idealizations, recognizing the hierarchy of different principles, applying equations containing multiple variables and understanding the cummulative effect of friction regarding dissipative losses.
Abstract Type: Contributed Poster Presentation
Session Time: Poster Session I
Poster Number: A80

Author/Organizer Information

Primary Contact: Claudia Schaefle
University of Applied Sciences of Rosenheim
Hochschulstr. 1
Rosenheim, Non U.S. 83024 Rosenheim, Germany
Phone: +49 - 8031 - 805 2419
and Co-Presenter(s)
Christian Kautz

Abteilung für Fachdidaktik der Ingenieurwissenschaften
am Zentrum für Lehre und Lernen (ZLL)
Technische Universität Hamburg

Am Schwarzenberg-Campus 3
21073 Hamburg

Tel:  +49-40-42878-4259

Contributed Poster

Contributed Poster: Download the Contributed Poster