Progress in Doppler picture velocimetry (DPV)

Seiler, F.; George, A.; Srulijes, J.; Havermann, M.

doi:10.1007/s00348-007-0447-3

Cited by 7 publications

(6 citation statements)

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“…The velocity-dependent phase shift of these fringes is then determined with an image processing. The developed DPV system consists of a cwargon ion laser emitting at 514.5 nm and a charge coupled device (CCD) camera with 1374 × 1024 pixels and a shutter time of 2 ms [48]. An image series was not acquired, but CCD cameras usually provide a maximal frame rate of <60 Hz.…”

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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“…Calculated FDM fringe visibility for varying levels of phase drift during data acquisition. work by Seiler et al [9], in which polarization division multiplexing (PDM) was used to separate the signal and reference fringe patterns, incomplete separation of the two images is reported but the level of this crosstalk is not quantified. However, in similar full-field imaging instrumentation using PDM, crosstalk of up to 20% has been reported [25].…”

Section: Channel Crosstalkmentioning

confidence: 99%

“…Using Eqs. (8) and (9), it can be seen that the number of channels required for the FDM noise to be equal to or less than that of using sequential recording and that for frame averaging the number of channels can be found from…”

Section: A Camera Dynamic Rangementioning

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%

“…If the images necessary to evaluate the reference and signal phases are captured sequentially, then errors can be introduced due to drifts in both the laser frequency and the interferometric path length [11]. The majority of previously reported I-PDV systems have used the sequential approach, with only the work by Seiler et al [9] proposing a solution in the form of polarization multiplexing to capture a zero-flow reference image simultaneously with images of the flow. However, this approach suffers from crosstalk between the signal and reference channels, which distorts the phase measurements and requires a more complex setup using polarization-sensitive optics and a second camera.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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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