Monochromatic heterodyne fiber-optic profile sensor for spatially resolved velocity measurements with frequency division multiplexing

Thorsten Pfister, Lars Büttner, Katsuaki Shirai, Jürgen Czarske

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

Investigating shear flows is important in technical applications as well as in fundamental research. Velocity measurements with high spatial resolution are necessary. Laser Doppler anemometry allows nonintrusive precise measurements, but the spatial resolution is limited by the size of the measurement volume to ∼ 50 μm. A new laser Doppler profile sensor is proposed, enabling determination of the velocity profile inside the measurement volume. Two fringe systems with contrary fringe spacing gradients are generated to determine the position as well as the velocity of passing tracer particles. Physically discriminating between the two measuring channels is done by a frequency-division-multiplexing technique with acousto-optic modulators. A frequency-doubled Nd: YAG laser and a fiber-optic measuring head were employed, resulting in a portable and flexible sensor. In the center of the measurement volume of ∼ 1-mm length, a spatial resolution of ∼5 μm was obtained. Spatially resolved measurements of the Blasius velocity profile are presented. Small velocities as low as 3 cm/s are measured. The sensor is applied in a wind tunnel to determine the wall shear stress of a boundary layer flow. All measurement results show good agreement with the theoretical prediction.

Original languageEnglish
Pages (from-to)2501-2510
Number of pages10
JournalApplied Optics
Volume44
Issue number13
DOIs
Publication statusPublished - 2005 May 1
Externally publishedYes

Fingerprint

Frequency division multiplexing
frequency division multiplexing
Fiber optic sensors
velocity measurement
Volume measurement
Velocity measurement
fiber optics
sensors
profiles
Lasers
Sensors
spatial resolution
Boundary layer flow
Shear flow
Modulators
Fiber optics
Wind tunnels
Shear stress
Optics
velocity distribution

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

Cite this

Monochromatic heterodyne fiber-optic profile sensor for spatially resolved velocity measurements with frequency division multiplexing. / Pfister, Thorsten; Büttner, Lars; Shirai, Katsuaki; Czarske, Jürgen.

In: Applied Optics, Vol. 44, No. 13, 01.05.2005, p. 2501-2510.

Research output: Contribution to journalArticle

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