(145e) A Learning Lesson From Thermodynamics: Ideal Fluids. Not True in Transport!

Many of us would most likely remember that Thermodynamics was not a trivial subject from a learning point of view. However, the instructor began the course by first introducing the basic concepts and behaviors of ideal fluids and mixtures. Therefore, the ideal gas law was an important learning tool to describe the system behaviors in many topics. Likewise, ideal mixtures were very useful when the focus switched to systems with more than one component. Only after students have mastered a good level of understanding of this subject, real gases and fluids as well as real mixtures were introduced.

The picture described above is entirely different when one analyzes the textbooks related to the subject of transport phenomena, with the exception of the analysis of hydrostatics. Here, the nature of the fluid from the point of view of the ideal vs. real behavior is irrelevant since the fluid velocity is zero. As soon as the focus of the subject switches to fluid motion, the textbook introduces the not so very inviting tetrahedral domain analysis of tensors (?) and stresses and incorporates them into the momentum conservation equation. This is done at a point where students do not even understand motion. Moreover, ideal fluids are considered in many textbooks as a graduate level subject!

In this contribution, the authors introduce a very systematic analysis of the momentum conservation equation by using ideal fluids. The efforts will show the enhancing effect on learning by following the analysis of different cases without the complications of viscous flows and the associated viscous flow theory. This contribution also introduces an effective way of studying the cases of viscous flows after many of the basic cases of motion have been studied with ideal fluids. Illustrative examples and discussion will be offered in the presentation.