A new laser vorticity probe - LAVOR: Its development and validation in a turbulent boundary layer

Vorticity measurements, which are scarce at the present time, can provide valuable dynamical information, particularly in unsteady and separated flows. Advances in laser Doppler anemometry and optical techniques have furnished the opportunity for the development of a nonintrusive vorticity probe with very fine spatial and temporal resolutions. The laser vorticity probe (LAVOR), which makes use of minimal laser beams and optical components, is capable of measuring velocity gradients with a separation distances as small as 0.3 mm. Velocity gradients are measured using two points on the same probe volume. However, unlike other techniques, the LAVOR also provides the instantaneous velocity at each point in the probe volume, and so provides additional dynamical information. The LAVOR probe was used in a fully turbulent two-dimensional boundary layer, and the data obtained are compared with the existing hot-wire vorticity data obtained in the same wind tunnel facility and with data obtained in other facilities. The spatial resolution is of the order of three Kolmogorov microscale units.