A single-headed fibre optic laser Doppler anemometer probe for the measurement of flow angles

Byrne, Gerald D.; James, Stephen W.; Tatam, Ralph P.

doi:10.1088/0957-0233/15/1/001

Cited by 28 publications

(7 citation statements)

References 30 publications

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“…This technique, using multimode fiber, is first reported by Dyott 13 for studying Brownian motion, and subsequently for LDV by Nishihara et al 14 using single-mode fiber. Similar techniques but with variable reference signal strength obtained from wavelength-dependent reflection off fiber Bragg grating have been reported by Byrne et al 15 Low-coherence techniques for Doppler velocimetry using either multimode laser diodes 16 or light-emitting diodes 17 have also been reported.…”

Section: Introductionsupporting

confidence: 64%

Fiber optic reflectometer for velocity and fraction ratio measurements in multiphase flows

Chang

Lim

2003

Review of Scientific Instruments

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Reply to "Comment on 'Fiber optic reflectometer for velocity and fraction ratio measurements in multiphase flows' " [Rev. Sci. Instrum. 74, 3559 (2003)] Rev. Sci. Instrum. 75, 286 (2004); 10.1063/1.1634361Comments on "Fiber optic reflectometer for velocity and fraction ratio measurements in multiphase flows" [Rev.A technique based on the coherent mixing of scattered signal with Fresnel reflection signal from the tip of an optical fiber is used to demonstrate the feasibility of measuring the velocity and fraction ratio of solid particles and gas bubbles or liquid droplets in a liquid or gas flow. If the liquid or gas flow is seeded with small neutrally buoyant particles, the technique is then capable of measuring the velocity as well as the fraction ratio of all three phases of the flow at a given point. The method is briefly described as follows. An optical signal derived from a diode laser driven by a constant current is launched into a single-mode optical fiber and transmitted, through a fiber coupler, to the signal fiber inserted into the test fluid. The diode laser used is a multilongitudinal mode device that has a low coherence length of about 200 m. The coherently mixed signal propagates back to the signal fiber, through the fiber coupler, and detected by a detector. By analyzing the signal, the velocity and fraction ratio of each phase can be obtained. Using water seeded with small solid particles and air bubbles, it is demonstrated that the technique is capable of measuring the velocity in the direction parallel to the fiber. Since the only intrusion to the fluid is the tiny fiber probe ͑a dimension of 125 m in diameter͒, the disturbance to most fluid flows is negligible, therefore, the technique is nearly nonintrusive.

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Section: Introductionsupporting

confidence: 64%

Fiber optic reflectometer for velocity and fraction ratio measurements in multiphase flows

Chang

Lim

2003

Review of Scientific Instruments

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“…When transformed through the matrix in the system the error levels for u and v remained the on the order of 0:01 m=s, whereas the w component increased to the order of 0:1 m=s. As a point of reference, Byrne et al [18] with a similar fivebeam system had documented errors of 1 to 3 deg. The probability density function based on the velocity data suggests that the error of the Reynolds stresses are on the order of 0:1 m 2 =s 2 for u 0 u 0 , v 0 v 0 , and u 0 v 0 .…”

Section: Methodsmentioning

confidence: 99%

“…The beam wavelengths correspond to the measurements of u 2 , u 1 , and u 3 , respectively, for the violet, blue, and green beams. A general representation of these three directions is in [18]. The beam pattern (five beams) was a cross with the center consisting of overlapping green and blue beams.…”

Section: Methodsmentioning

confidence: 99%

Effect of Aspect Ratio on Flow Through Serpentine Nozzles

Reynolds

Reeder

2012

Journal of Aircraft

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The flowfields for two rectangular cross-sectional nozzles with two in-plane 90 deg bends were investigated both experimentally and computationally. The cross-sectional planform of the two nozzles were of opposite aspect ratios (2:1 and 1:2). The Reynolds number (based upon the hydraulic diameter and mean velocity within the nozzle) was 1:4 10 4 , providing a Dean number of 8400 (based upon radius of curvature at the centerline of the nozzle). The experimental portion of the study was conducted by three-component laser Doppler velocimetry using a five-beam probe. A computational study was performed on the interior of the nozzle using a commercial code that employed a Reynolds stress model. With noted exceptions, good correlation was observed between the computational and experimental solutions. Secondary-flow velocities at the nozzle exit revealed evidence of a complex pattern of streamwise vortices generated by the two bends. It was found that despite the common Dean number, the difference in aspect ratio led to substantially different velocity fields. The flow was dominated by a single pair of counterrotating streamwise vortices in one case, whereas its counterpart yielded a complex pattern of multiple smaller vortices.

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“…This arrangement used a number of innovative technologies at the time, for example, circulaser technology combined with high power single frequency laser diodes, birefringent fiber coupled Bragg cells and a fiber optic reference beam channel constructed in birefringent fiber including the coupler. This technology was subsequently used to measure flow angles for gas turbine applications and incorporated in-fiber Bragg grating (FBG) stabilization of the laser diode emission frequency [20]. A difficulty with the use of the reference beam channel is that the geometry means the fringes are closely spaced and therefore for commercially available processors operating at 100 MHz-200 MHz the measured velocity component is limited to about 40 ms 1 , which is insufficient for high speed applications where flow velocities of hundreds of meters per second may need to be measured.…”

Section: Laser Velocimetrymentioning

confidence: 99%