Browsing by Author "Jermy, Mark C."
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Item Open Access Crossed source-detector geometry for a novel spray diagnostic: Monte Carlo simulation and analytical results(Osa Optical Society of America, 2005-05-01T00:00:00Z) Berrocal, Edouard; Churmakov, D. Y.; Romanov, V. P.; Jermy, Mark C.; Meglinski, I. V.Sprays and other industrially relevant turbid media can be quantitatively characterized by light scattering. However, current optical diagnostic techniques generate errors in the intermediate scattering regime where the average number of light scattering is too great for the single scattering to be assumed, but too few for the diffusion approximation to be applied. Within this transitional single-to-multiple scattering regime, we consider a novel crossed source-detector geometry that allows the intensity of single scattering to be measured separately from the higher scattering orders. We verify Monte Carlo calculations that include the imperfections of the experiment against analytical results. We show quantitatively the influence of the detector numerical aperture and the angle between the source and the detector on the relative intensity of the scattering orders in the intermediate single-to-multiple scattering regime. Monte Carlo and analytical calculations of double light-scattering intensity are made with small particles that exhibit isotropic scattering. The agreement between Monte Carlo and analytical techniques validates use of the Monte Carlo approach in the intermediate scattering regime. Monte Carlo calculations are then performed for typical parameters of sprays and aerosols with anisotropic (Mie) scattering in the intermediate single-to-multiple scattering regime.Item Open Access Low and high orders light scattering in particulate media(2004-07-12T00:00:00Z) Meglinski, I. V.; Romanov, V. P.; Churmakov, D. Y.; Berrocal, Edouard; Jermy, Mark C.; Greenhalgh, D. A.We present the results of a theoretical study providing details of propagation of laser radiation within disperse randomly inhomogeneous intermediately single- to-multiple scattering media. A quantitative analysis of scattering orders in the transition from single to multiple scattering is presented. Crossed source- detector fiber optics geometry used to separate the intensity of single scattering from higher scattering orders. The results demonstrate good agreement between analytical and Monte Carlo techniques. This validates the use of the Monte Carlo approach in the intermediate single-to-multiple scattering regime. The method used can be applied to verify analytical results against experiment via the Monte Carlo calculations that include imperfections of the experiment.Item Open Access New model for light propagation in highly inhomogeneous polydisperse turbid media with applications in spray diagnostics(Optical Society of America (OSA), 2005-11-14T00:00:00Z) Berrocal, Edouard; Meglinski, I. V.; Jermy, Mark C.Modern optical diagnostics for quantitative characterization of polydisperse sprays and other aerosols which contain a wide range of droplet size encounter difficulties in the dense regions due to the multiple scattering of laser radiation with the surrounding droplets. The accuracy and efficiency of optical measurements can only be improved if the radiative transfer within such polydisperse turbid media is understood. A novel Monte Carlo code has been developed for modeling of optical radiation propagation in inhomogeneous polydisperse scattering media with typical drop size ranging from 2 µm to 200 µm in diameter. We show how strong variations of both particle size distribution and particle concentration within a 3D scattering medium can be taken into account via the Monte Carlo approach. A new approximation which reduces ~20 times the computational memory space required to determine the phase function is described. The approximation is verified by considering four log-normal drop size distributions. It is found valid for particle sizes in the range of 10-200 µm with increasing errors, due to additional photons scattered at large angles, as the number of particles below than 10 µm increases. The technique is applied to the simulation of typical planar Mie imaging of a hollow cone spray. Simulated and experimental images are compared and shown to agree well. The code has application in developing and testing new optical diagnostics for complex scattering media such as dense spr