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A Laboratory Exercise To Teach The Hydrostatic Principle As A Core Concept In Fluid Mechanics

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2009 Annual Conference & Exposition


Austin, Texas

Publication Date

June 14, 2009

Start Date

June 14, 2009

End Date

June 17, 2009



Conference Session

Interdisciplinary and Multidisciplinary Laboratories

Tagged Division

Division Experimentation & Lab-Oriented Studies

Page Count


Page Numbers

14.37.1 - 14.37.29



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Paper Authors


Robert Edwards Pennsylvania State University, Erie

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Robert Edwards is currently a Lecturer in Engineering at The Penn State Erie, The Behrend
College where he teaches Statics, Dynamics, and Fluid and Thermal Science courses. He earned a
BS degree in Mechanical Engineering from Rochester Institute of Technology and an MS degree in Mechanical Engineering from Gannon University.

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Gerald Recktenwald Portland State University

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Gerald Recktenwald is an Associate Professor in the Mechanical and Materials Engineering
Department at Portland State University. He is a member of ASEE, ASME, IEEE and SIAM. His
research interests are in fluid mechanics, heat transfer, applications of numerical analysis, and in improving undergraduate engineering education.

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Brian Benini Case Western Reserve University

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Brian Benini is a 2008 Mechanical Engineering Technology graduate of Penn State Behrend. He is now pursuing a Master of Science degree in Materials Science and Engineering at Case Western Reserve University in Cleveland, OH. His thesis work involves fracture and fatigue behavior of implantable medical wires.

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NOTE: The first page of text has been automatically extracted and included below in lieu of an abstract

A Laboratory Exercise to Teach the Hydrostatic Principle as a Core Concept in Fluid Mechanics


Every field of study has core concepts that are essential to the understanding of the material. Students must understand these concepts and use them as a foundation for further study in the field. Most students carry preconceived ideas based on previous life experiences into the classroom which may conflict with the concepts being taught. These misperceptions can be difficult to overcome. It is common for students to take the material presented in a lecture and try to reconcile the new information with their preconceived ideas. This creates problems for both the instructor who is trying to instill these core concepts and the students who struggle with the conflicts.

One approach to overcome these problems is to create a laboratory experience that will help the students to face their misperceptions and replace them with the appropriate core concept. The authors are currently investigating this approach as it relates to the fluid and thermal sciences.

One of the key core concepts in the area of fluid mechanics is the hydrostatic principle relating the pressure in a fluid to the depth of the fluid. A common misperception is that the pressure is a function of the weight of the fluid above the point of interest when it is actually a function of the depth of the fluid column. This paper describes a laboratory exercise designed to teach this concept to the students. While a description of the apparatus and the test will be included, the focus of the paper will be on some of the results of the exercise to date, qualitative conclusions based on observing the exercise, and some suggestions for further refinements of the exercise.

The assessment data which is discussed in the paper tends to indicate that students do not have a hard time comprehending the basic principle but do run into difficulty when trying to apply their understanding to practical problems. The laboratory exercise has been used during three different courses covering Mechanical Engineering, Civil Engineering, Mechanical Engineering Technology and Electrical Engineering Technology students at both Penn State Erie and Portland State University. Different assessment tools were used each time the exercise was run since they were being developed and modified during that time. Each time the results related to applications have been similar. This is discussed in the paper.


The exercise documented in this paper is part of a National Science Foundation funded project being jointly conducted at Penn State Erie, The Behrend College (PSB) and Portland State University (PSU). It is one in a suite of seven exercises being developed by the authors which are intended to help teach core principles in the thermal and fluid sciences through the use of everyday devices. These include a hair dryer, a bicycle pump, a blender, a computer power supply, a toaster, straight and stepped tanks, and a pipe section with a change of area. The project was first introduced at the 2007 ASEE national convention in a paper presented in the

Edwards, R., & Recktenwald, G., & Benini, B. (2009, June), A Laboratory Exercise To Teach The Hydrostatic Principle As A Core Concept In Fluid Mechanics Paper presented at 2009 Annual Conference & Exposition, Austin, Texas. 10.18260/1-2--4645

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