Design and Development of a Pneumatic Atomizer for Seeding Tracers in Piv Experiments

Particle image velocimetry (PIV) is a state-of-the-art experimental technique for nonintrusive determination of instantaneous fluid velocity. Tracer particles, seeded into the flow, are captured by a camera as a sequence of images that are subsequently processed using a standard image processing algorithm. The intensity field of the two subsequent images is cross-correlated. The instantaneous point velocity of the fluid is obtained using the cross-correlation matrix and the time difference between subsequent frames. Tracer particles play a crucial role in determining the accuracy of PIV results. The current work aims to develop a low-cost pneumatic atomizer for generating fine droplets of different fluids under a wide range of operating pressures. To that end, a simple tube-in-tube atomizer is developed and housed on a manifold. The size distribution of the generated aerosol particles is determined using the theory of Mie scattering. Further, the particles are used to determine the velocity profile of a low Re flow in a rectangular duct. Strong agreement between the experimental and analytically obtained profiles suggests that the atomizer is suitable for PIV seeding.