Other keywords: volumetric reconstruction, camera calibration, 3D-3C particle tracking velocimetr... more Other keywords: volumetric reconstruction, camera calibration, 3D-3C particle tracking velocimetry ABSTRACT : A technique for full-three dimensional flow mapping based on a tomographic reconstruction of the observation volume is developed by Elsinga (1). Based on the projection of multi-camera system with their orientation known from prior calibration procedure, the 3D light intensity distribution of the observation volume are reconstructed. A 3D observation space reconstruction is performed by iterative reconstruction techniques like MART (multiplicative algebraic reconstruction technique) algorithm. The method is further modified to a rapid and less memory intensive reconstruction technique (2).These algorithms have been modified to apply for PTV (3, 4). The objective of the present work is to modify and incorporate this tomographic reconstruction schemes in time resolved volumetric particle tracking and thereby performing full 3D flow diagnostics. The partcile mask correration op...
Digital holography appears to be the next-generation technology for holographic diagnostics of pa... more Digital holography appears to be the next-generation technology for holographic diagnostics of particle fields and has been applied to holographic particle tracking flow measurements. In the digital holography, the Fresnel or Fourier holograms are recorded directly by the CCD or CMOS cameras and stored digitally. No film material involving wet-chemical or other processing is necessary as in optical holography. The reconstruction of the wave-field, which is done optically by illumination of a hologram, is performed by numerical methods. Digital holography also enables the use of complex amplitude information inaccessible by optical reconstruction, thereby allowing flexible reconstruction algorithms to achieve optimization of specific information. However, due to the poor pixel resolution of CCD or CMOS cameras as compared to that of holographic films, the digital holography gives poor depth resolution for images. This problem severely impairs the usefulness of digital holography espe...
ABSTRACT A new improved ant colony optimization (ACO) based algorithm has been developed for temp... more ABSTRACT A new improved ant colony optimization (ACO) based algorithm has been developed for temporal particle matching in 2-D and 3-D particle tracking velocimetry (PTV). Two of the present authors have already applied the ant colony optimization (ACO) based algorithm effectively and successfully to the time differential particle pairing process of particle tracking velocimetry (PTV). In the present study, the algorithm has been further improved for the reduced com putation time as well as for the same or slightly better particle pairing results than that of the authors’ previous ACO algorithm. This improvement is mainly achieved due to the revision of the selection probability and pheromone update formulae devised specially for the purpose of accurate and fast computation. In addition, the new algorithm also provides better matching results when dealing with the loss-of-pair particles (i.e., those particles which exist in one frame but do not have their matching pair in the other frame), a typical problem in the real image particle tracking velocimetry. The performance of the new improved algorithm is tested with 2-D and 3-D standard particle images with successful results.
A data validation technique for 3-D particle tracking velocimetry is proposed. Rule based fuzzy l... more A data validation technique for 3-D particle tracking velocimetry is proposed. Rule based fuzzy logic system has been used. In the proposed scheme, the PTV pairing results will be provided as an input to the validating system. Then, velocity vectors of the particles in the neighborhood are measured, in terms of velocity gradient, direction and magnitude. The distance between vector midpoints, difference in vector magnitudes, average value of vector magnitude and the sum of the squares of the differences of the x, y and z-components of the velocity vectors are used as reference parameters for evaluation. Depending upon the combination of the values of these different parameters the fuzzy logic system will check how much the vectors are likely to be declared as true vectors in terms of numerical parameter called confidence. Higher value of confidence shows that the vectors under consideration as true while the vectors are likely to be erroneous for lower value of confidence. The resul...
Etude de l'ecoulement bidimensionnel incompressible autour d'un profil d'aile soumis ... more Etude de l'ecoulement bidimensionnel incompressible autour d'un profil d'aile soumis impulsivement a des mouvements combines de translation et d'oscillation en tangage. On examine les effets produits par de grands angles d'attaque, de grandes amplitudes et de grandes frequences reduites sur le decrochage instationnaire du profil. On emploie plusieurs methodes de visualisation qui donnent soit des reseaux de lignes de courant, soit des filets d'emission. Analyse des evolutions de l'ecoulement proche du profil. Observation du sillage dans son entier
Other keywords: volumetric reconstruction, camera calibration, 3D-3C particle tracking velocimetr... more Other keywords: volumetric reconstruction, camera calibration, 3D-3C particle tracking velocimetry ABSTRACT : A technique for full-three dimensional flow mapping based on a tomographic reconstruction of the observation volume is developed by Elsinga (1). Based on the projection of multi-camera system with their orientation known from prior calibration procedure, the 3D light intensity distribution of the observation volume are reconstructed. A 3D observation space reconstruction is performed by iterative reconstruction techniques like MART (multiplicative algebraic reconstruction technique) algorithm. The method is further modified to a rapid and less memory intensive reconstruction technique (2).These algorithms have been modified to apply for PTV (3, 4). The objective of the present work is to modify and incorporate this tomographic reconstruction schemes in time resolved volumetric particle tracking and thereby performing full 3D flow diagnostics. The partcile mask correration op...
Digital holography appears to be the next-generation technology for holographic diagnostics of pa... more Digital holography appears to be the next-generation technology for holographic diagnostics of particle fields and has been applied to holographic particle tracking flow measurements. In the digital holography, the Fresnel or Fourier holograms are recorded directly by the CCD or CMOS cameras and stored digitally. No film material involving wet-chemical or other processing is necessary as in optical holography. The reconstruction of the wave-field, which is done optically by illumination of a hologram, is performed by numerical methods. Digital holography also enables the use of complex amplitude information inaccessible by optical reconstruction, thereby allowing flexible reconstruction algorithms to achieve optimization of specific information. However, due to the poor pixel resolution of CCD or CMOS cameras as compared to that of holographic films, the digital holography gives poor depth resolution for images. This problem severely impairs the usefulness of digital holography espe...
ABSTRACT A new improved ant colony optimization (ACO) based algorithm has been developed for temp... more ABSTRACT A new improved ant colony optimization (ACO) based algorithm has been developed for temporal particle matching in 2-D and 3-D particle tracking velocimetry (PTV). Two of the present authors have already applied the ant colony optimization (ACO) based algorithm effectively and successfully to the time differential particle pairing process of particle tracking velocimetry (PTV). In the present study, the algorithm has been further improved for the reduced com putation time as well as for the same or slightly better particle pairing results than that of the authors’ previous ACO algorithm. This improvement is mainly achieved due to the revision of the selection probability and pheromone update formulae devised specially for the purpose of accurate and fast computation. In addition, the new algorithm also provides better matching results when dealing with the loss-of-pair particles (i.e., those particles which exist in one frame but do not have their matching pair in the other frame), a typical problem in the real image particle tracking velocimetry. The performance of the new improved algorithm is tested with 2-D and 3-D standard particle images with successful results.
A data validation technique for 3-D particle tracking velocimetry is proposed. Rule based fuzzy l... more A data validation technique for 3-D particle tracking velocimetry is proposed. Rule based fuzzy logic system has been used. In the proposed scheme, the PTV pairing results will be provided as an input to the validating system. Then, velocity vectors of the particles in the neighborhood are measured, in terms of velocity gradient, direction and magnitude. The distance between vector midpoints, difference in vector magnitudes, average value of vector magnitude and the sum of the squares of the differences of the x, y and z-components of the velocity vectors are used as reference parameters for evaluation. Depending upon the combination of the values of these different parameters the fuzzy logic system will check how much the vectors are likely to be declared as true vectors in terms of numerical parameter called confidence. Higher value of confidence shows that the vectors under consideration as true while the vectors are likely to be erroneous for lower value of confidence. The resul...
Etude de l'ecoulement bidimensionnel incompressible autour d'un profil d'aile soumis ... more Etude de l'ecoulement bidimensionnel incompressible autour d'un profil d'aile soumis impulsivement a des mouvements combines de translation et d'oscillation en tangage. On examine les effets produits par de grands angles d'attaque, de grandes amplitudes et de grandes frequences reduites sur le decrochage instationnaire du profil. On emploie plusieurs methodes de visualisation qui donnent soit des reseaux de lignes de courant, soit des filets d'emission. Analyse des evolutions de l'ecoulement proche du profil. Observation du sillage dans son entier
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