Faculty Publications
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Publications by NITK Faculty
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Item Active contours technique for fringe evaluation of complicated fringe patterns(2010) Joishi, R.; Reddy, K.P.J.; Hegde, G.M.An improved technique based on active contours approach is presented for the analysis of non-uniform finite fringe interferograms. The technique is validated by demonstrating its application in analyzing the interferomertic image having non-uniform fringe pattern generated by a supersonic flow in front of a blunt body. A filtering method for identifying the flow parameters is presented as an extension of this technique. Proposed technique also provides an estimate of the heterodyning spatial frequency. © 2010 SPIE.Item Quantitative density imaging of subsonic jet using planar laser induced fluorescence of MEK(2012) Shelar, M.S.; Umesh, G.; Hegde, G.M.; Jagadeesh, G.; Reddy, K.P.J.Quantitative molecular density distribution of Methyl ethyl ketone (MEK) in turbulent nitrogen jet (Re≈2-3×103) was measured using PLIF technique. The tracer (MEK) was seeded in the nitrogen jet by purging through the liquid MEK at ambient temperature. Planar laser sheet from frequency quadrupled, Q-switched, Nd: YAG laser (266 nm) was used as an excitation source. Emitted fluorescence images of jet flow field were recorded on CMOS camera. To obtain quantitative density profile, the dependence of PLIF intensity on MEK partial pressure was employed. Thus an instantaneous quantitative density image of nitrogen jet, seeded with MEK was obtained. © 2012 IEEE.Item Visualization of coherent structures in turbulent subsonic jet using planar laser induced fluorescence of acetone(2013) Shelar, V.M.; Hegde, G.M.; Umesh, G.; Jagadeesh, G.; Reddy, K.P.J.In this paper, we present the molecular density distribution measurement in turbulent nitrogen jet (Re ? 3×103), using acetone as molecular tracer. The tracer was seeded in the nitrogen jet by purging through the liquid acetone at ambient temperature. Planar laser sheet of 266 nm wavelength from frequency quadrupled, Q-switched, Nd:YAG laser was used as an excitation source. Emitted fluorescence images of jet flow field were recorded on CMOS camera. The dependence of planar laser induced fluorescence (PLIF) intensity on acetone vapor density was used to convert PLIF image of nitrogen jet into the density image on pixel-by-pixel basis. Instantaneous quantitative density image of nitrogen jet, seeded with acetone, was obtained. The arrowhead-shaped coherent turbulent structures were observed in the present work. It was found that coherent structures were non-overlapping with separate boundaries. Breaking of coherent structures into turbulence was clearly observed above four times jet width. © EDP Sciences, 2013.Item Gas phase oxygen quenching studies of ketone tracers for laser-induced fluorescence applications in nitrogen bath gas(2014) Shelar, V.M.; Hegde, G.M.; Umesh, G.; Jagadeesh, G.; Reddy, K.P.J.In this paper we report the quantitative oxygen quenching effect on laser-induced fluorescence of acetone, methyl ethyl ketone, and 3-pentanone at low pressures (?700 torr) with oxygen partial pressures up to 450 torr. Nitrogen was used as a bath gas in which these molecular tracers were added in different quantities according to their vapor pressure at room temperature. These tracers were excited by using a frequency-quadrupled, Q-switched, Nd:YAG laser (266 nm). Stern-Volmer plots were found to be linear for all the tracers, suggesting that quenching is collisional in nature. Stern-Volmer coefficients (ksv) and quenching rate constants (kq) were calculated from Stern-Volmer plots. The effects of oxygen on the laser-induced fluorescence of acetone, methyl ethyl ketone, and 3-pentanone were compared with each other. Further, the Smoluchowski theory was used to calculate the quenching parameters and compared with the experimental results. Copyright © Taylor & Francis Group, LLC.