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Project
Ontwikkeling van een remote sensing-techniek voor druppeltjes en deeltjes in de lucht met behulp van glory en spikkelpatronen (IWT668)
Since 1990, more than one hundred engine power-loss events have occurred, on both commuter and large transport airplanes, due to the presence of ice crystals in convective weather. These incidents could have been prevented if a reliable particle characterization instrument would have been available. In some cases, in order to avoid these hazardous conditions, pilots have been using a visual inspection of what is known as the glory optical phenomenon. This phenomenon is an interference pattern that appears when the liquid water droplets in the clouds scatter the sun light at an angle of 180° (full backscatter). During my Research Master thesis, different interference patterns that appear in the backscatter region were studied in order to detect ice formation within single water droplets. The glory phenomenon was used here to determine the diameter of single water droplets. Although the conclusions obtained by this study are still far from being applicable, the promising results motivate this project to further investigate these phenomena.
The final aim of this project is thus to use the backscattered laser light to develop a quantitative and reliable measurement technique for particle characterization. The mentioned technique will allow us to measure size distribution and concentration of a wide range of particles (spherical and transparent droplets, irregular and opaque particles) in the size range from microns to several millimeters. Up to date, several optical characterization principles and even commercial instruments already exist (e.g. based on laser scattering, digital imaging and laser diffraction). These techniques are very useful at lab scale, but they have important limitations in case of in-situ and harsh environments.
Therefore, the technique developed during this project, which is not limited to lab scale, is not only essential for aircraft safety, but can be used as well in many other applications, such as spray characterization for the pharmaceutical and agricultural industry, painting, liquid metals cooling, fire safety, etc. In order to develop a technique based on the interference patterns that appear in the backscattered light, i.e. the glory and speckle patterns, a systematic approach with increasing problem complexity is proposed. A preliminary study of these phenomena will be performed through the investigation of the interference patterns produced by single particles. Afterwards, the glory and the speckle pattern will be investigated for multiple droplets (first liquid water sprays and then flows of ice or sand particles).
Finally, mixed phase conditions will be investigated. Common tasks exist for the different kind of particles, i.e.: the correct understanding of the phenomena, the development of a suitable inversion algorithm for particle size determination and the validation of the technique. This project will benefit from the collaboration of two laboratories: the Environmental and Applied Fluid Dynamics department of the von Karman Institute (VKI-EA) and the department of Mechanical Engineering in the Vrije Universiteit Brussel (VUB-MECH). The VKI has ample experience in optical techniques and in the development of new optical instrumentation (Particle Image Velocimetry in 1980, first precommercial Laser Doppler Velocimetry in 1972, Global rainbow instrument in 1999). Furthermore, it possesses several wind tunnels and optical facilities, which make the VKI an excellent environment to develop the project. In addition, VUB-MECH has vast experience in system identification and inverse problems. Through this collaboration, the project will benefit from all the necessary tools and knowledge needed to bring it to a successful end .
The final aim of this project is thus to use the backscattered laser light to develop a quantitative and reliable measurement technique for particle characterization. The mentioned technique will allow us to measure size distribution and concentration of a wide range of particles (spherical and transparent droplets, irregular and opaque particles) in the size range from microns to several millimeters. Up to date, several optical characterization principles and even commercial instruments already exist (e.g. based on laser scattering, digital imaging and laser diffraction). These techniques are very useful at lab scale, but they have important limitations in case of in-situ and harsh environments.
Therefore, the technique developed during this project, which is not limited to lab scale, is not only essential for aircraft safety, but can be used as well in many other applications, such as spray characterization for the pharmaceutical and agricultural industry, painting, liquid metals cooling, fire safety, etc. In order to develop a technique based on the interference patterns that appear in the backscattered light, i.e. the glory and speckle patterns, a systematic approach with increasing problem complexity is proposed. A preliminary study of these phenomena will be performed through the investigation of the interference patterns produced by single particles. Afterwards, the glory and the speckle pattern will be investigated for multiple droplets (first liquid water sprays and then flows of ice or sand particles).
Finally, mixed phase conditions will be investigated. Common tasks exist for the different kind of particles, i.e.: the correct understanding of the phenomena, the development of a suitable inversion algorithm for particle size determination and the validation of the technique. This project will benefit from the collaboration of two laboratories: the Environmental and Applied Fluid Dynamics department of the von Karman Institute (VKI-EA) and the department of Mechanical Engineering in the Vrije Universiteit Brussel (VUB-MECH). The VKI has ample experience in optical techniques and in the development of new optical instrumentation (Particle Image Velocimetry in 1980, first precommercial Laser Doppler Velocimetry in 1972, Global rainbow instrument in 1999). Furthermore, it possesses several wind tunnels and optical facilities, which make the VKI an excellent environment to develop the project. In addition, VUB-MECH has vast experience in system identification and inverse problems. Through this collaboration, the project will benefit from all the necessary tools and knowledge needed to bring it to a successful end .
Datum:1 jan 2014 → 15 apr 2018
Trefwoorden:mechanica
Disciplines:Mechanica niet elders geclassificeerd