Cfd Simulation

For the generation and production of a spray the knowledge of information like the desired droplet size and its distribution is of fundamental importance. In order to characterise a spray correctly, one has to know the droplet size distribution of the droplets, which were generated out of a given liquid. In many applications it is desired to produce very small droplets. For the design and lay out of inhalers for example, it is necessary to achieve droplet sizes not larger than approximately 10 μm to be absorbed by the lungs. When one designs an atomisation nozzle in view of the desired droplet size distribution, one has to make sure via measurements, that the nozzle is really able the produce the expected droplet size distribution within an acceptable uncertainty range. Besides the droplet size distribution, the droplet velocity is an important parameter since it is a measure of the droplet momentum.

The particle image velocimetry (PIV) is an optical noninvasive working flow velocity measurement method. The flow field is made visible by introducing into the fluid small buoyancy neutral particles – the so called tracers. The particle flow then is illuminated with the aid of a light sheet and recorded at two defined different times within a small time interval with a digital camera. Because the particle move within this time interval with the flow, one can calculate the particles velocity by knowing its path between the two moments of illumination. The result is a velocity vector field of the flow. Here, we assume that the particles are small and follow the flow without any slip. Compared to local methods like LaserDopplerVelocimetry (LDV) with the ParticleImageVelocimetry one can reconstruct a whole flow region An extension of ParticleImageVelocimetry is the combination of PIV with thermometry (PIV/T).