Nonmechanical cross-sectional scanning laser Doppler velocimeter with directional discrimination of transverse velocity component

Abstract

We propose a nonmechanical cross-sectional scanning laser Doppler velocimeter (LDV) with directional discrimination of the transverse velocity component. In the proposed LDV, a combination of changes in wavelength and the port of the fiber array between the main body and probe are used to scan the measurement position on a two-dimensional (2-D) cross-sectional plane that is perpendicular to the direction of flow. Optical frequency shifting using acousto-optic modulators (AOMs) is employed to discriminate the direction of the transverse velocity component. Polarization multiplexing is used to transmit frequency-shifted beams from the main body to the probe. The experimental results reveal that the 2-D scanning function and introduction of directional sensitivity are successfully achieved.

Design of low-loss Nb2O5-based grating coupler in scanning differential laser-Doppler integrated probe for cross-sectional velocity distribution measurement

“…Scanning techniques have been applied to differential laser Doppler velocimetry for acquiring information about the velocity distribution. To measure one-dimensional (1D) or two-dimensional (2D) velocity distribution, a mechanical scanning technique, 1 – 4 nonmechanical scanning technique, 5 – 9 and spatial encoding technique 10 – 12 have been developed in laser Doppler velocimetry. Among many applications that are related to velocity distribution measurement, information about the velocity distribution in a 2D cross section of the flow is often required in applications such as fluid flow measurements in pipes.…”

Proposal and design of integrated probe based on silicon photonics for laser Doppler cross-sectional velocity distribution measurement

“…Various types of mechanical scanning differential LDVs have been reported, [6][7][8][9][10] in which moving lenses, 6) diffraction gratings, 7) mirrors, 8,9) or transparent plates 10) are used in their transmitting optics for scanning the measurement point. A nonmechanical scanning technique [11][12][13][14][15] that uses diffraction gratings as dispersive elements makes it feasible to realize a compact and reliable probe. However, the system would be complicated if one intends to measure the velocity distribution in two dimensions.…”

All-Fiber Configuration Laser Self-Mixing Doppler Velocimeter Based on Distributed Feedback Fiber Laser

“…The traditional Laser Doppler Velocimeter (LDV) [1,2,3] based on two beam interference have been widely applied in optical sensor and industrial areas [4,5,6,7], on account of the advantages of anti-interference, fast dynamic response, and non-contact measurement. However, there still exist many restrictions in practical application, such as complex light path and high reference beam requirement.…”