Assessing the infinitely expanding intersection region for the development of large-scale multipoint laser Doppler velocimetry

Abstract Multipoint laser Doppler velocimetry (MLDV) has been effective for non-invasively measuring the flow velocity distribution with a high-spatial and high-time resolution. The flow velocity can be estimated using a scattered light signal by seeding particles passing through a fringe pattern formed in the intersection region of two laser beams. The shape of this intersection region can be easily changed by changing the optical components and positions of the lasers. An infinitely expanding intersection region is proposed in the present paper. A wide intersection region was indicated by the measurement results of flow velocity. The intersection region is evaluated using a flow channel (1.4 mm × 1.4 mm). The area of the operating measurement region exceeds 150 mm in the horizontal direction and is less than ±10 mm in the vertical direction. This new MLDV is referred to as a large-scale MLDV.