Real Time Flow Sensing - Cylinder Wake Turbulence Measurements Using Piezoelectrics

Collecting fluid flow information typically requires expensive, intrusive, and technically complex instruments. This study investigates a cost-effective and minimally invasive method for measuring turbulent flow using a voltage-generating piezo- electric strip. Open channel tests were conducted with a slender, highly flexible membrane placed in the wake of a cylinder, allowing for non-intrusive flow measurement. The wakes behind two separate cylinder diameters (3.175 cm and 1.27 cm) were measured at varying Reynolds number and streamwise distances in the wake. Turbulent pressure fluctuations were converted to voltage outputs, and spectral analysis identified Karman vortex shedding modes and frequencies. By positioning the piezoelectric strip at various distances along the cylinder wake, results indicated that increasing the Reynolds number significantly impacts the piezoelectric voltage response when the strip is closer to the cylinder. Acoustic tests were also performed to assess any facility noise that could interfere with the piezoelectric readings. This low-cost and simple sensor presents a practical alternative to traditional methods for measuring turbulence in situations requiring immediate or low-fidelity feedback in fluid flow application.