Particle Image Velocimetry (PIV) is used to measure particular features of flow fields, including vortices, shock waves and other flow phenomena.
The PIV measurement technique records the displacement of very small tracer particles that are injected into the flow. Separate photos taken at ultra-short intervals of as little as 20 microseconds enable measurements of the speed and direction of the particles and hence the air flow. Subsequent plotting on a vector map shows the structure of air flow, for instance the velocity distribution in a tip vortex.
DNW applies both two-component and three velocity component (3C-PIV) measurements. Measuring the third velocity component requires at least two cameras directed to a laser light sheet at oblique angles. 3C-PIV measurements are applied at both low and high speeds, including transonic speeds in DNW´s HST tunnel in Amsterdam and the transonic tunnel TWG in Göttingen.