Background extraction from double-frame PIV images

Honkanen, Markus; Nobach, Holger

doi:10.1007/s00348-004-0916-x

Cited by 50 publications

(35 citation statements)

References 9 publications

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“…In Theunissen et al (2008), different methods are presented at the image preprocessing, correlation and data postprocessing stages of the PIV procedure to account for the presence of solid, fixed wall boundaries. Honkanen and Nobach (2005) proposed a background extraction method based on the assumption that noise sources can be discriminated from the particle images by their relative displacement, a condition which is not fulfilled in free surface flows. Digital masks are binary matrices containing ones at the pixel locations of interest and zeros elsewhere.…”

Section: Introductionmentioning

confidence: 99%

Dynamic masking of PIV images using the Radon transform in free surface flows

Sanchis

Jensen

2011

Exp Fluids

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Particle image velocimetry (PIV) processing of free surface flow images often requires the use of digital masks to overcome the problems caused by the interface. In cases where a large number of particle images are collected it is essential that the time-varying boundary between the two phases can be tracked automatically to produce the binary masks. The Radon transform-based technique presented in this paper allows the automatic detection of the air-water interface in a stream of particle images acquired from a single camera. It is applied to time-resolved PIV measurements in the liquid phase of a stratified multiphase flow in a circular pipe. Accuracy estimations are provided using synthetic and real wave profiles. An extension to the more complex case of an overturning wave is also discussed.

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Section: Introductionmentioning

confidence: 99%

Dynamic masking of PIV images using the Radon transform in free surface flows

Sanchis

Jensen

2011

Exp Fluids

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“…In PIV experiments, the fluid of interest is seeded with fluorescent dyed micrometer or submicrometer scale freefloating probe particles [5][6][7]. The full field-of-view (FOV) of epifluorescent imaging optics is used to observe a part of the channel illuminated by a sheet of bright light, such as high power pulse lasers with a wavelength corresponding to the fluorescence excitation of the tracer particles.…”

Section: Introductionmentioning

confidence: 99%

Experimentally investigation of the CCD binning option in particle imaging velocimetry measurements of laminar flows

Akselli

Teke

2011

Int. J. Metrol. Qual. Eng.

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Abstract. In this work we present an experimental investigation of the employment usage application of the vertical pixel binning (PB) option for PIV (particle image velocimetry) measurements. The PB option increases the speed of a CCD, at the cost of loosing spatial resolution. Consequently, it is expected that PB will positively impact the dynamic velocity range of the PIV measurements. In order to show the benefit of the CCD PB option in PIV measurements, we have carried out series of microPIV experiments on laminar flows, seeded with 1 µm fluorescent polystyrene microparticles and passing through a 200 µm × 200 µm × 50 000 µm microchannel. The flow images were recorded at normal, 2 × 1, and 3 × 1 vertical PB modes of a monochrome CCD camera. The experimentally obtained velocity profiles were calculated using the ensemble-averaged cross-correlation method and Gaussian sup-pixel interpolation and then compared with theoretically calculated velocity profiles. We found that the error introduced by the PB option did not exceed the inherent uncertainty of the PIV system used. For a particular PIV system CCD camera, using the PB option allowed an increase in the dynamic velocity range of a PIV system by more than a factor of two, without extra investments.

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“…Laser intensity can vary between images or image pairs due to differences in the two lasers (in case of a double-pulsed YAG laser), objects or bubbles can introduce strong reflections of light, and/or reflection from channel walls in confined flows introduce glow. Several approaches are available in literature to tackle these problems (Seol and Socolofsky 2008;Lindken and Merzkirch 2002;Honkanen and Nobach 2005;Westerweel 1993;Shavit et al 2007;Theunissen et al 2008). In the presence of static objects or in two-phase flow, fluorescent particles and a color filter are often used to avoid interference of the object edges in the correlation map.…”

Section: Introductionmentioning

confidence: 99%

“…The use of an additional camera can be circumvented by removing the stationary objects through a background subtraction, which will leave moving tracer particles in the image as suggested by Honkanen and Nobach (2005). Image normalization to cope with uneven illumination was already suggested by Westerweel (1993).…”

Section: Introductionmentioning

confidence: 99%

On image pre-processing for PIV of single- and two-phase flows over reflecting objects

et al. 2010

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A novel image pre-processing scheme for PIV of single-and two-phase flows over reflecting objects which does not require the use of additional hardware is discussed. The approach for single-phase flow consists of image normalization and intensity stretching followed by background subtraction. For two-phase flow, an additional masking step is added after the background subtraction. The effectiveness of the pre-processing scheme is shown for two examples: PIV of single-phase flow in spacer-filled channels and two-phase flow in these channels. The preprocessing scheme increased the displacement peak detectability significantly and produced high quality vector fields, without the use of additional hardware.

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Background extraction from double-frame PIV images

Cited by 50 publications

References 9 publications

Dynamic masking of PIV images using the Radon transform in free surface flows

Dynamic masking of PIV images using the Radon transform in free surface flows

Experimentally investigation of the CCD binning option in particle imaging velocimetry measurements of laminar flows

On image pre-processing for PIV of single- and two-phase flows over reflecting objects

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