FIEVel: a Fast InExpensive Velocimeter based on an optical mouse sensor

Velocity measurement in fluids is essential for many applications spanning research, education, and industry. This presentation will discuss the development and application of FIEVel, a low cost, high sample rate, optical fluid velocimeter. State-of-the-art methods such as hot-wire anemometry, laser doppler velocimetry, acoustic doppler velocimetry, and particle image velocimetry (PIV) are typically intrusive, offer a low sample rate, or have a high cost. Using an optical sensor developed for commercially available computer mice, we demonstrate nonintrusive, time-resolved, 2-component, pointwise velocity measurements in the bulk of a flowing fluid at sample rates over 6 kHz, validated by direct comparison with high frame rate PIV. Our device uses inexpensive and interchangeable lenses intended for webcams and a custom 3D-printed housing with integrated focus adjustment. The device design, build documentation, supporting software, and operating guidelines are being released as an open-science hardware project and can be reproduced for less than $100 in materials. As an application example, we showcase the sensor's ability to resolve temporal spectra in grid generated turbulence.