Work-in-Progress: Visualization and Simulation of the Thermal Boundary Layer around a Cylinder as a Classroom Demonstration

This paper presents the educational application of shadowgraphy in visualizing thermal boundary layers. The thermal boundary layer concept is an abstract topic due to the difficulty of direct observation. In this work, we use a collimated light beam for illumination and a camera with a telecentric lens to visualize the thermal boundary layer that forms around a heated copper tube placed in a tank containing cold still water. The video clearly shows the initial diffusive growth of the boundary layer and the subsequent onset of buoyant convection. Then when flow is initiated, a thinning of the boundary layer on the upstream side of the cylinder is clearly visible. After showing video clips in two sections of an Introduction to Transport Phenomena course, student feedback was very positive; they found it interesting and helpful. We believe this visual representation aids in learning and can actively engage students in the learning process.