ABSTRAKT

This report presents experimental results on the propagation of a turbulent front induced by an oscillating grid starting from rest. The study is divided into two parts. The purpose of a first investigation is to validate vorticity measurements for the detection of the turbulent/non-turbulent interface for oscillating grid turbulence. This is done using particle image velocimetry (PIV) and resolving the larger scales of the flow. The results of these measurements show, that level-based detection of a turbulent front is well applicable to an unsteady flow, such as grid turbulence advancing into a fluid at rest. Secondly, 3D scanning particle tracking velocimetry (3D-SPTV) was used to yield Lagrangian flow information at the turbulent/non-turbulent interface with focus on the smaller scales.