Soap film visualization of low velocity flow over roughness elements

In this study we discuss estimates for the minimum Reynolds number at which vortex shedding occurs using a soap-film tunnel. The goal is to observe the flow over a series of roughness elements. The soap film tunnel generates a nearly two-dimensional fluid flow, achieving Reynolds numbers below 100 to study this phenomenon. A high-speed camera recording the thin film at 5000 fps, and MATLAB are the main tools used to extract data from the experiments. Test pieces with a length of 25.4 mm and width between 0.1194 mm and 0.1524 mm are inserted into the film. The boundary layer will be visualized, and the occurrence of vortex shedding will be determined. Measurements of the vortex speed and shedding frequency will be taken and compared with results from other studies.