Research Description

Development of a Flow Seeding System for Particle Image Velocimetry

Particle Image Velocimetry (PIV) is a non-intrusive optical technique used to measure velocity information in fluid flows. The system consists of tracer particles that are impregnated in the flow, a laser and optical arrangement to illuminate the particles, and a camera to capture the light scattered by the particles. A local velocity vector can be computed by measuring the particle displacement in two successive exposures and dividing by the elapsed time. PIV can capture the entire two-dimensional velocity field of a fluid flow. Flow seeding is a critical part of PIV experiments. This is because the tracer particle velocities are measured rather than the actual fluid velocity field. Thus, it is critical that the particles follow the fluid. Several advantages and disadvantages exist for different sizes and types of particles, such as their ability to follow, their light scattering efficiency, and toxicity. Some common tracer particles used in gas flows are polystyrene, metal oxides, smoke, and various oils. Particle diameters are typically on the order of a micron.

The proposed study is to design and construct a PIV flow seeding system for the University of Florida Anechoic Wind Tunnel. The wind tunnel contains a 29 in. by 44 in. by 72 in. open-jet test section with a velocity range of 15-75 m/s. The wind tunnel configuration poses several design challenges. Since it is an open-circuit tunnel, tracer particles cannot be reused, and new particles must be constantly introduced to the flow. The high volumetric flow rate of the tunnel requires a large number of seeding particles. This study will include analysis of various tracer particle types and seeding methods, fluid dynamic characterization of the tracer particles, and development of a particle delivery system to the test section. The proposed PIV seeding system will provide a consistent basis for aerodynamic measurement in the facility and help elucidate the fundamental fluid dynamic characteristics of various devices.