Global Doppler frequency shift detection with near-resonant interferometry

Landolt, Andrin; Roesgen, T.

doi:10.1007/s00348-009-0688-4

Cited by 12 publications

(11 citation statements)

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“…An image series was not acquired, but CCD cameras usually provide a maximal frame rate of <60 Hz. In order to increase the sensitivity of the MI, a dispersive element (iodine vapor cell) was inserted in the reference path by Landolt and Rösgen in 2009 [49,50]. Furthermore, a normal CCD and an intensified CCD camera with an image resolution of 1008 × 1008 and 1280 × 1024 pixels are applied, respectively.…”

Section: Amplitude-based Signal Evaluationmentioning

confidence: 99%

Imaging Flow Velocimetry with Laser Mie Scattering

Fischer

2017

Applied Sciences

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Abstract:Imaging flow velocity measurements are essential for the investigation of unsteady complex flow phenomena, e.g., in turbomachines, injectors and combustors. The direct optical measurement on fluid molecules is possible with laser Rayleigh scattering and the Doppler effect. However, the small scattering cross-section results in a low signal to noise ratio, which hinders time-resolved measurements of the flow field. For this reason, the signal to noise ratio is increased by using laser Mie scattering on micrometer-sized particles that follow the flow with negligible slip. Finally, the ongoing development of powerful lasers and fast, sensitive cameras has boosted the performance of several imaging methods for flow velocimetry. The article describes the different flow measurement principles, as well as the fundamental physical measurement limits. Furthermore, the evolution to an imaging technique is outlined for each measurement principle by reviewing recent advances and applications. As a result, the progress, the challenges and the perspectives for high-speed imaging flow velocimetry are considered.

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Section: Amplitude-based Signal Evaluationmentioning

confidence: 99%

Imaging Flow Velocimetry with Laser Mie Scattering

Fischer

2017

Applied Sciences

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“…The system illustrated uses three illumination directions and a single I-PDV imaging head to measure three different velocity components. The I-PDV imaging head shown uses a Michelson interferometer, as this is the most commonly reported configuration [10,[13][14][15]. However the technique is equally applicable to single-component velocity measurements, and to the Mach-Zehnder interferometer (MZI) configuration previously reported [11,12] and used in the experimental section of this work.…”

Section: Fdm For I-pdvmentioning

confidence: 99%

“…Interferometric planar Doppler velocimetry (I-PDV) describes a group of techniques (Doppler picture velocimetry [8][9][10], Mach-Zehnder interferometric PDV [11,12], and near-resonant interferometry [13,14]) that use optical interferometry to make planar velocity measurements and attempt to overcome some of the limitations of molecularfilter-based PDV. In I-PDV, the molecular filter is replaced with a path-length imbalanced interferometer, and the Doppler-shifted light causes a change in the light intensity distribution in the recorded interference pattern.…”

Section: Introductionmentioning

confidence: 99%

“…The magnitude of this change is proportional to the flow velocity and the path-length imbalance in the interferometer. I-PDV has been used for both flow visualization [8] and quantitative velocity measurements [11][12][13][14][15] by evaluating the interferometric phase change that occurs when the light is Doppler frequency shifted. The relationship between the Doppler frequency shift, Δν, the optical path length imbalance, Δl, and the change in the phase difference Δϕ is given by…”

Section: Introductionmentioning

confidence: 99%

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Frequency division multiplexing for interferometric planar Doppler velocimetry

et al. 2014

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A new method of acquiring simultaneously the signal and reference channels used for interferometric planar Doppler velocimetry is proposed and demonstrated. The technique uses frequency division multiplexing (FDM) to facilitate the capture of the requisite images on a single camera, and is suitable for time-averaged flow measurements. Furthermore, the approach has the potential to be expanded to allow the multiplexing of additional measurement channels for multicomponent velocity measurement. The use of FDM for interferometric referencing is demonstrated experimentally with measurements of a single velocity component of a seeded axisymmetric air jet. The expansion of the technique to include multiple velocity components was then investigated theoretically and experimentally to account for bandwidth, crosstalk, and dynamic range limitations. The technique offers reduced camera noise, automatic background light suppression, and crosstalk levels of typically <10%. Furthermore, as this crosstalk is dependent upon the channel modulations applied, it can be corrected for in postprocessing.

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“…The technique has been successfully applied in fullscale wind tunnels (Beutner et al 1998), high-speed flows (Smith et al 1996) and combustion measurements (Roehle et al 2000). Molecular line filters can also be used to change the Doppler frequency shift into a phase shift as it is done in near resonant interferometry (Landolt et al 2009) to measure velocity distributions. However, those methods usually suffer from uncertainties in the order of a few m/s (Elliott et al 1999).…”

Section: Introductionmentioning

confidence: 98%