Nonlinear diffusion filtering of images obtained by planar laser-induced fluorescence spectroscopy

Malm, Henrik; Sparr, Gunnar; Hult, Johan; Kaminski, Clemens F.

doi:10.1364/josaa.17.002148

Cited by 41 publications

(21 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The tablet cores consisted of excipients and the active pharmaceutical ingredient (API) and were covered with different cosmetic or enteric coatings. The OCT images presented were further processed with a nonlinear diffusion filter as reported in Ref 15. (see Supplementary Appendix for detailed information).…”

Section: Methodsmentioning

confidence: 99%

Imaging pharmaceutical tablets with optical coherence tomography

Mauritz

Morrisby

Hutton

et al. 2010

Journal of Pharmaceutical Sciences

Self Cite

View full text Add to dashboard Cite

Section: Methodsmentioning

confidence: 99%

Imaging pharmaceutical tablets with optical coherence tomography

Mauritz

Morrisby

Hutton

et al. 2010

Journal of Pharmaceutical Sciences

Self Cite

View full text Add to dashboard Cite

“…6d) and so reduce the number of erroneous curves detected by later gradient operations. The NLD filter has already been successfully applied to detect the edge of OH regions in a diffusion flame using an explicit numerical iterative scheme (Malm et al 2000). Schießl et al (1999) have also applied the NLD filter to OH PLIF images from a two-stroke optically accessible research engine.…”

Section: Image Processingmentioning

confidence: 99%

Local curvature measurements of a lean, partially premixed swirl-stabilised flame

2011

View full text Add to dashboard Cite

A swirl-stabilised, lean, partially premixed combustor operating at atmospheric conditions has been used to investigate the local curvature distributions in lifted, stable and thermoacoustically oscillating CH 4 -air partially premixed flames for bulk cold-flow Reynolds numbers of 15,000 and 23,000. Single-shot OH planar laser-induced fluorescence has been used to capture instantaneous images of these three different flame types. Use of binary thresholding to identify the reactant and product regions in the OH planar laser-induced fluorescence images, in order to extract accurate flame-front locations, is shown to be unsatisfactory for the examined flames. The Canny-Deriche edge detection filter has also been examined and is seen to still leave an unacceptable quantity of artificial flame-fronts. A novel approach has been developed for image analysis where a combination of a non-linear diffusion filter, Sobel gradient and thresholdbased curve elimination routines have been used to extract traces of the flame-front to obtain local curvature distributions. A visual comparison of the effectiveness of flamefront identification is made between the novel approach, the threshold binarisation filter and the Canny-Deriche filter. The novel approach appears to most accurately identify the flame-fronts. Example histograms of the curvature for six flame conditions and of the total image area are presented and are found to have a broader range of local flame curvatures for increasing bulk Reynolds numbers. Significantly positive values of mean curvature and marginally positive values of skewness of the histogram have been measured for one lifted flame case, but this is generally accounted for by the effect of flame brush curvature. The mean local flame-front curvature reduces with increasing axial distance from the burner exit plane for all flame types. These changes are more pronounced in the lifted flames but are marginal for the thermoacoustically oscillating flames. It is concluded that additional fuel mixture fraction and velocimetry studies are required to examine whether processes such as the degree of partial-premixedness close to the burner exit plane, the velocity field and the turbulence field have a strong correlation with the curvature characteristics of the investigated flames.

show abstract

“…As part of this procedure any stretch, rotation, and vertical shifts between the instantaneous power profile image and the OH image were corrected for. An anisotropic nonlinear diffusion filter was applied 40 to reduce the level of noise and to enhance gradients in the images. The images were resized to 50% of their original size after filtering which yields a signal to noise ratio gain of around 4.…”

Section: Extraction Of Flame Frontmentioning

confidence: 99%

Effect of heat release on turbulence and scalar-turbulence interaction in premixed combustion

et al. 2008

View full text Add to dashboard Cite

Stereoscopic particle image velocimetry and planar laser induced fluorescence measurements of hydroxyl radical are simultaneously applied to measure, respectively, local turbulence intensities and flame front position in premixed ethylene-air flames stabilized on a bluff body. Three different equivalence ratios, 0.55, 0.63, and 0.7, and three different Reynolds numbers, 14 000, 17 000, and 21 000, are considered. Laser measurements were made for five different flame configurations within the ranges above and in the corresponding cold flows. By comparing the measurements of the cold and the corresponding hot flows, the effect of heat release on the turbulence and its interaction with the flame front is studied. All the flames are in the thin reaction zone regime. Typical flow features forming behind the bluff body are observed in the cold flows, whereas in the reacting flows the mean velocities and thus the shape, size, and characteristics of the recirculating eddy behind the bluff body are strongly influenced by the heat release. The strong acceleration across the mean flame and the radial outward shift of the stagnation plane of the recirculating eddy yield negative radial velocities which are absent in the corresponding cold flow cases. The spatial intermittency of the flame front leads to an increase in the turbulent kinetic energy. Although a decrease in the mean and rms values of the strain rate tensor e ij components is observed for the reacting case as one would expect, the local flow acceleration across the flame front leads to a substantial increase in the skewness and the kurtosis of the probability density functions ͑PDFs͒ of e ij components. The turbulence-scalar interaction is studied by analyzing the orientation of the flame front normal with the eigenvectors of e ij . The PDFs of this orientation clearly show that the normals have an increased tendency to align with the extensive strain rate, which implies that the scalar gradients are destroyed by the turbulence as the scalar isosurfaces are pulled apart. This result questions the validity of passive scalar turbulence physics commonly used for premixed flame modeling. However, the influence of Lewis number on this alignment behavior is not clear at this time.

show abstract

Nonlinear diffusion filtering of images obtained by planar laser-induced fluorescence spectroscopy

Cited by 41 publications

References 17 publications

Imaging pharmaceutical tablets with optical coherence tomography

Imaging pharmaceutical tablets with optical coherence tomography

Local curvature measurements of a lean, partially premixed swirl-stabilised flame

Effect of heat release on turbulence and scalar-turbulence interaction in premixed combustion

Contact Info

Product

Resources

About