We propose a two-dimensional scanning laser Doppler velocimeter (LDV) that does not require any moving mechanisms in its probe. In the proposed LDV, the measurement position can be scanned in two dimensions on a cross-sectional plane perpendicular to the direction of flow. The combination of the change in wavelength and change in port of the fiber array input to the probe is utilized for the scan. The experimental results using a sensor probe setup indicate that the measurement position can be scanned in two dimensions using the proposed method. The scanning range was estimated to be 39.7 mm in the axial direction over the wavelength range of 1536-1554 nm and 26.1 mm in the transverse direction for the use of 22 ports of the fiber array.
An axial scanning laser Doppler velocimeter (LDV) with directional discrimination not requiring any moving mechanism in its probe is proposed. The proposed LDV utilizes frequency shift induced by acousto-optic modulators (AOMs) for discriminating the direction of velocity. The measurement position is axially scanned by changing the wavelength of the light input to the probe. The experimental result reveals that both the axial scan and the directional discrimination can be realized by using the proposed method without any moving element in the probe.
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.
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