Application of Doppler global velocimetry in cryogenic wind tunnels

Willert, Christian; Stockhausen, Guido; Beversdorff, Manfred; Klinner, Joachim; Lempereur, Christine; Barricau, P.; Quest, Jürgen; Jansen, Uwe

doi:10.1007/s00348-004-0914-z

Cited by 41 publications

(27 citation statements)

References 12 publications

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“…Figure 9 shows the views after this de-warping process; here all four views have been overlaid for demonstration purposes. A similar multi-branch imaging fibre bundles system has been described by Willert et al 15 . In order to measure all three components of velocity it is necessary to view from at least three directions, however the imaging fibre bundle in use has four channels.…”

Section: B Extension To Multiple Velocity Components and 3d 2-pdv Mmentioning

confidence: 98%

Single Camera 3D Planar Doppler Velocimetry Using Two Frequency Planar Doppler Velocimetry (2v-PVD) and Imaging fibre bundles

Charrett

Ford

Tatam

2006

44th AIAA Aerospace Sciences Meeting and Exhibit

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A modified Planar Doppler Velocimetry (PDV) technique, two frequency PDV (2-PDV), is described that allows measurements of the velocity field over a plane defined by a laser light sheet using sequential illumination of the flow with two closely separated (~1GHz) frequencies of laser light. This allows a common-path imaging head to be used containing a single CCD camera instead of the usual camera pair. The problem of image misalignment is now avoided and the polarisation sensitivity of the beam splitter used in two camera imaging heads is also removed. Cost efficiency is improved by the simplification of the system. This paper describes the development of a 2-PDV system using a continuous wave argon ion laser capable of making time-averaged velocity measurements. Initially a single velocity component system was constructed using acousto-optic modulators to produce the two illumination frequencies required. The system was then expanded to make 3D velocity measurements using a single CCD camera and multiple coherent imaging fibre bundles. Measurements were made on the rotating disc, in order to assess error level in the measurements, and on a seeded axisymmetric air jet. A method of improving the sensitivity of the 2-PDV system is demonstrated by using both the rising and falling slopes of the iodine absorption line. Reductions in the error levels of velocity measurements of approximately 40% can be achieved using this increased sensitivity method.

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Section: B Extension To Multiple Velocity Components and 3d 2-pdv Mmentioning

confidence: 98%

Single Camera 3D Planar Doppler Velocimetry Using Two Frequency Planar Doppler Velocimetry (2v-PVD) and Imaging fibre bundles

Charrett

Ford

Tatam

2006

44th AIAA Aerospace Sciences Meeting and Exhibit

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“…A comparison between the PIV and the DGV technique, which are the furthermost developed field measurement techniques based on the time-of-flight and the Doppler principle, respectively, is found in [136] with respect to their physical measurement capabilities. For instance, DGV is capable of coping with high seeding concentrations, and it is not necessary to resolve single particles or patterns of multiple particles in the image.…”

Section: Space Measurementmentioning

confidence: 99%

“…A textbook that summarizes the manifold DGV applications does not exist, because the absolute number of groups working with DGV is very low. For a comparison between PIV and DGV, we refer the reader to the work of Willert et al [136], who applied both techniques in large-scale wind tunnels.…”

Section: Application Examples Challenges and Perspectivesmentioning

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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“…17. This approach has proved very flexible, achieving high quality flow field measurements and was adopted by the German Aerospace Center (DLR) for measurements in the European transonic wind tunnel [33] and by NASA [34].…”

Section: Laser Velocimetrymentioning

confidence: 99%