Qualitative analysis of the capillary flow stability of spurting materials by using transmitted light intensity measurements

B.M. Marín Santibañez, F. Rodríguez González, J. Pérez-González, L.A. Vega Acosta M., E. Moreno García

Abstract


The stability in the capillary flow of spurting materials was analyzed by following the temporal variation of their average birefringence. Two different fluids were analyzed, a high-density polyethylene melt, and an aqueous micellar solution of Cetylpyridinium Chloride and Sodium Salicylate. Birefringence changes were detected through measurements of the transmitted light intensity and video images of the flow channel. Transmitted light intensity measurements were more sensitive and provided better information about the flow stability than pressure ones. An unstable flow region was present in the micellar solution before the onset of spurt. Also, there were periodic changes in the optical properties of both fluids, in the spurt region and at higher shear rates, which indicate that the flow is also unstable in the high shear rate branch, in contrast to the generalized assumption of the stable flow in such regime. Several frequency components of the transmitted light intensity were observed, coincident with different spurts, in the unstable flow regimes for both fluids. Finally, an outstanding decrease in the transmitted light intensity was observed in both fluids under flow conditions where slip was present.

Keywords


Flow instabilities; slip; birefringence; high-density polyethylene; micellar solutions

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REVISTA MEXICANA DE FÍSICA, year 67, issue 2, March-April 2021. Bimonthly Journal published by Sociedad Mexicana de Física, A. C. Departamento de Física, 2º Piso, Facultad de Ciencias, Universidad Nacional Autónoma de México, Ciudad Universitaria, Alcaldía Coyacán, C.P. 04510 , Ciudad de México. Apartado Postal 70-348. Tel. (+52)55-5622-4946, https://rmf.smf.mx/ojs/rmf, e-mail: rmf@ciencias.unam.mx. Chief Editor: José Alejandro Ayala Mercado. INDAUTOR Certificate of Reserve: 04-2019-080216404400-203, ISSN: 2683-2224 (on line), 0035-001X (print), both granted by Instituto Nacional del Derecho de Autor. Responsible for the last update of this issue, Technical Staff of Sociedad Mexicana de Física, A. C., Fís. Efraín Garrido Román, 2º. Piso, Facultad de Ciencias, Universidad Nacional Autónoma de México, Ciudad Universitaria, Alcaldía Coyacán, C.P. 04510 , Ciudad de México. Date of last modification, March 1st., 2021.

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