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Updated: Aug 14, 2026

High-speed Particle Image Velocimetry Near Surfaces
Published on: June 24, 2013
Effect of element beam quality degradation on coherently combined vortex beams and rotational Doppler velocimetry
Abstract:
Vortex beams are important for rotational Doppler velocimetry, but the influence of element beam quality degradation on coherently combined vortex beams remains insufficiently clarified. Based on a compact honeycomb phased-array geometry with the central channel closed, this work uses the surrounding 18 effective sub-apertures to form coherently combined vortex beams. A radial high-order-mode degradation model described by M2 is introduced. The target vortex-mode purity ηl is defined by the normalized full complex-field overlap with the M2=1.0 reference vortex field. Unlike prior studies mainly focused on turbulence-induced OAM degradation, adaptive beam formation, or rotational Doppler velocimetry algorithms, this work isolates the transmitting-element beam-quality tolerance and quantifies its transfer to Doppler peak identifiability. The results show that ηl decreases from 1.000 at M2=1.0 to 0.0305 at M2=3.0, and this degradation further affects rotational Doppler velocimetry performance under turbulence propagation.
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