Fig. 1: Neutrally buoyant, helium filled soap bubbles for large scale Particle Image Velocimetry of air flows
Measurement of convective air flow on large scales, e.g. in aircraft cabins or aircraft cabin models, is achieved applying an advanced Particle Image Velocimetry (PIV) technique. By combination of neutrally buoyant Helium filled soap bubbles (HFSBs) as tracer particles with quality switched solid state lasers of high pulse energy as light source instantaneous velocity fields with dimensions as large as 12 m² can be measured (see Figure)A specifically designed HFSB generator allows for generating neutrally buoyant HFSBs with dimensions of only a fraction of a millimetre with high efficiency. Due to the high seeding densities, which can be achieved with this set up, PIV algorithms can be used in order to determine instantaneous velocity fields with high lateral resolution. As a consequence this method is particularly useful for investi gating unsteady flows like e.g. convective air flow.