Two-point correlation estimation of turbulent shear flows using a novel laser Doppler velocity profile sensor

In this paper we describe, for the first time, a new method of two-point correlation estimations of turbulent flows using a laser Doppler velocity profile sensor. For the spatial correlation estimations the laser Doppler velocity profile sensor offers unique opportunities since a high spatial resolution of approximately 20 micron within the measurement volume is achieved. Furthermore, the low relative velocity measurement uncertainty of about 0.1% yields a high resolution of small velocity fluctuations and, therefore, allows correlation investigations where such high resolution is required. Moreover, a new virtual detection volume technique is presented which is only applicable in conjunction with the laser Doppler velocity profile sensor and offers the potential to achieve highly precise spatial correlation estimations. Measurements have been carried out in the turbulent wake of a circular. Both temporal as well as spatial correlation estimations have been calculated from the acquired velocity data yielding a longitudinal Taylor microscale of 3.53 mm and a transverse Taylor microscale of 1.84 mm.