Highly precise correlation estimates of turbulent sheer flows using a novel laser doppler profile sensor

For the characterisation of small vortices within turbulent flow fields the Taylor length scale is often used. This length scale can be extrapolated out of two-point correlation estimations for which the flow velocity has to be measured precisely at two different positions in the flow. The application of the laser Doppler velocity profile sensor, which offers a high spatial resolution within the measurement volume (around 10 μm) and a low velocity measurement uncertainty of about 0.1 %, for vortex investigations is, therefore, an interesting novel approach. Moreover, the system offers the advantage of extrapolating the Taylor length scale with data from only one sensor which is not possible with conventional laser Doppler velocimetry. Due to the high spatial resolution of profile sensor, problems which occur when the detection volumes overlap do not occur in contrast to conventional systems. We present measurements which have been carried out in the turbulent wake of a circular cylinder. Both temporal as well as spatial correlation estimations have been calculated out of the acquired velocity data.