Particle-image-velocimetry

A further area of activity of Suvis is the development and application of modern numerical methods for the calculation (prediction) of flows using CFD in industry, science etc. Our employees are especially trained in view of technical applications of numerical flow simulations. Within the recent years we conducted several projects in the area of multiphase flows. We dealt with applications in the optimisation of processes in chemical engineering, the transport of particles, gas cleaning and particle separation from gases and liquids, and the calculation and optimisation of cyclone separators. We apply powerful commercial software tools like grid generators in order to generate numerical grids using CADdata in a short time for even complex applications. Also, for flow calculations and the evaluation of 3D flow fields we apply powerful software solutions. Furthermore, for certain individual problems we apply codes we have developed our selves.

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.

Particle size measurements are important in various applied sciences and in engineering, for example in fuel burning or in cavitation research as well as in particle size control. In all these applications it necessary to have knowledge about the particle dynamics. To gain that knowledge one has to measure the particle size and its velocity if possible in a noninvasive way with high local and temporal resolutions. A device which makes such measurements possible is the so called PhaseDopplerAnemometer (PDA), which has several advantages. First, it exhibits a large dynamic range from micrometer particles up to sizes in the millimetre range. Then it is very precise and no calibration procedure is necessary. Moreover, it is very robust against optical distortions. In the following the working principle of this flow and particle measurement technique will be explained.

The measurement technique of LaserDopplerVelocimetry (LDV) is one of the most frequently applied modern measurement techniques in fluid mechanics to perform accurate local flow velocity measurements, which exhibits the advantage of a very high local and temporal resolution. Our technical department offers excellent conditions to perform such measurements (LDV).