A cantilever piezoelectric beam immersed in a flow and subjected to naturally occurring vortices such as those formed in the wake of bluff bodies can be used to generate electrical energy harvested in fluid flows. In this paper, we present the pressure distribution and deflection of a piezoelectric beam subjected to controlled vortices. A custom designed experimental facility is set up to study the interaction of individual and multiple vortices with the beam. Vortex tori are generated by an audio speaker and travel at controlled rates over the beam. Particle image velocimetry is used to measure the 2-D flow field induced by each vortex and estimate the effect of pressure force on the beam deflection.

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In a classroom environment, after a comprehensive theoretical discussion of compressible flows, it is beneficial to conduct a visual experiment in which students can observe these flows and some of the features associated with them. Experimental study of compressible fluid dynamics is associated with high equipment costs; therefore, conducting an experiment is not feasible for some colleges. This article describes an experiment implemented at Manhattan College upper division and graduate fluid dynamics courses at a relatively low cost. In the experiment, a water table hydraulic analogy was used. Theoretical considerations of this analogy are explained in this article. An area–velocity relation was used to study the Mach number at the exit of a Laval nozzle. The theory and measurement came within 10% of each other, which is sufficient for a teaching demonstration. This exercise can be conducted in two class sessions: (1) discussing the theoretical considerations and (2) performing the experiment and analyzing data. The overall experience is a good way to help students understand some of the compressible flow features, and further promote their interest in fluid mechanics.

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In an effort to find a simple and efficient method for observing and predicting compressible flows in an instructional environment, we revisit the classical hydraulic analogy. The focus is made on using a water table apparatus to visualize the formation of oblique surface waves in a flow around a wedge. These waves are analogous to the oblique shock waves seen in a compressible flow. A mathematical derivation of this analogy is presented together with water table experiment data collected by graduate students. The comparison between the predicted values and measured values is made and shows a remarkable correlation between the two for simulated Mach numbers.