PIV for Peanuts - a Low Cost Particle Image Velocimetry System to Observe Terminal Velocity in Suspensions

Abstract:

Particle Image Velocimetry (PIV) is a proven technique for the observation of flow or particle motion in fluids. A pulsed laser is used to create a thin plane of light in the fluid, which typically contains a suspension of neutrally buoyant tracer particles. A high speed camera captures a sequence of images, which are processed to develop velocity vector fields from the particle motion.

During a wider study into the observation of particle and bubble terminal velocity in water using an acoustic backscatter profiler in a recirculating sediment tower, the acoustic data appeared to reveal a more complex flow regime than expected. To verify the acoustic results, PIV was selected as a potential approach to monitor particle motion in the region of the tank where acoustic observations were being made. Review of available PIV equipment showed that even systems designed for educational use would be beyond the budget of the planned experimental program.

A search of the cupboards yielded an alternative set of equipment with potential promise. A DIY laser level and an aging GoPro camera were pressed into action for a series of tests to investigate whether the combined equipment would be sufficiently sensitive and rapid to capture the particle motion satisfactorily. It would.

This paper describes the equipment configuration and the range of measurements achieved. Results from data processed with the open source PIVlab software tool are presented in the context of validating acoustic measurements of particle terminal velocity.