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Author(s): S. Nogueira
R. Sousa
J. B. L. M. Campos
A. M. F. R. Pinto
M. L. Riethmuller
Title: Simultaneous PIV and shadowgraphy measurements in slug flow in Newtonian and non-Newtonian liquids
Issue Date: 2002
Abstract: A recent technique for performing simultaneous Particle Image Velocimetry and Shadography appliedfor the first time to slug flow, is presented in this work. The unsteadiness of slug flow creates the needof recording the shadow of the Taylor bubbles at the precise instant and position of the PIVmeasurements. Therefore, this experimental technique is used in order to characterise simultaneouslythe flow in the liquid and the shape of a single gas slug (Taylor bubble) rising through a verticalcolumn of stagnant liquid using only one CCD camera. The experimental facility and technique aredescribed and the details of the synchronisation between the two techniques are also explained. Thisnew method is based on the fact that the PIV particles and the shadow of the bubbles can illuminate theCCD camera sensor at different gray levels. The PIV images are obtained by seeding the flow withfluorescent seeding and placing an optical filter in front of the camera so that the intense laserreflections in the interface are avoided and only the PIV particles reach the CCD sensor. Theshadowgraph images are obtained by backward illumination with a board of LEDs emitting light in awavelength that passes through the optical filter. The processing of the images is explained. Thereason for keeping recording images with 8 bits is discussed. During the post-processing it is possibleto combine the shadowgraph results with the velocity field acquired with PIV, therefore, solving someof the basic processing errors, which appear at the interfaces. Some limitations of the technique itself,due to the highly 3D shape of the rear of the bubbles are also discussed. The flow around a gas slugrising through a vertical column filled with a non-Newtonian fluid is also presented. These are the firstquantitative measurements in slug flow for non-Newtonian flows, as long as the authors are aware
Subject: Engenharia química, Engenharia química
Chemical engineering, Chemical engineering
Scientific areas: Ciências da engenharia e tecnologias::Engenharia química
Engineering and technology::Chemical engineering
Source: 11th International Symposium on Applications of Laser Techniques to Fluid Mechanics
Document Type: Artigo em Livro de Atas de Conferência Internacional
Rights: openAccess
Appears in Collections:FEUP - Artigo em Livro de Atas de Conferência Internacional

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