APPLICATION OF SHADOW DOPPLER VELOCIMETRY TO ARBITRARY-SHAPED DROPLET MEASUREMENT IN WATER SPRAY

The shadow Doppler velocimetry (SDV) is employed for measurements of arbitrarily-shaped droplets in a water spray. In a region of the spray sufficiently far from the breakup region of liquid film, where most of droplets are spherical, the size-velocity correlation measurement result by SDV shows good agreement with that obtained by the improved interferometric laser imaging technique. The SDV can be a lso applied to the breakup region where considerable number of droplets are in irregular shapes, showing statistically in terms of a shape index that the population of such droplets are higher than in the region sufficiently far from it. The present paper also demonstrates the performance of SDV equipped with two parallel fiber-array sensors, which is effective for the measurements of droplet t rajectory angles. The dependence of the a ngles on droplet diameters is presented, showing the larger inertia for the larger droplets. Furthermore, the stereoscopic measurement by two SDV optical systems is also conducted in order to capture the projection of droplet shapes from two different directions. The droplet shadows are observed in the breakup region at the edge of the spray cone. It can be found that, under the present measurement condition, the influence of the radial gradient of the a xisymmetric mean spray flow on droplet shapes is not dominantly strong.