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Measurement and observation of jet thrust for water flow through micro-orifice / Akiomi Ushida in Transactions of the ASME . Journal of fluids engineering, Vol. 134 N° 8 (Août 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 8 (Août 2012) . - 07 p. Titre : Measurement and observation of jet thrust for water flow through micro-orifice Type de document : texte imprimé Auteurs : Akiomi Ushida, Auteur ; Tomiichi Hasegawa, Auteur ; Takehiro Hoshina, Auteur Année de publication : 2012 Article en page(s) : 07 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : micro-orifice;  water;  jet  thrust;  jet  swell;  elastic  stress Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Owing to the many potential industrial and biological applications of microfluid mechanics, it has recently become an attractive research topic. However, researchers have mainly concentrated on microchannel flows and studies investigating micro-orifice flows are rare cases. In the present study, the results from experiments conducted on flows through micro-orifices with diameters of 100 µm, 50 µm, and 25 µm are presented. In these experiments, the thrust and diameter of observed outflow jets are measured. The resultant thrust and diameter of the jets for the 100 µm orifice flow agree with the numerical predictions obtained via the Navier–Stokes equations. Conversely, for an orifice with a diameter of 50 µm or less, it is found that the thrust is lower than that predicted and the existence of jet swell becomes apparent. With the estimated elastic stress proportional to squared mean velocity, a change in the elasticity of the water as it flows through a micro-orifice is strongly suggested. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000008 [...] [article] Measurement and observation of jet thrust for water flow through micro-orifice [texte imprimé] / Akiomi Ushida, Auteur ; Tomiichi Hasegawa, Auteur ; Takehiro Hoshina, Auteur . - 2012 . - 07 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 8 (Août 2012) . - 07 p. Mots-clés : micro-orifice;  water;  jet  thrust;  jet  swell;  elastic  stress Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Owing to the many potential industrial and biological applications of microfluid mechanics, it has recently become an attractive research topic. However, researchers have mainly concentrated on microchannel flows and studies investigating micro-orifice flows are rare cases. In the present study, the results from experiments conducted on flows through micro-orifices with diameters of 100 µm, 50 µm, and 25 µm are presented. In these experiments, the thrust and diameter of observed outflow jets are measured. The resultant thrust and diameter of the jets for the 100 µm orifice flow agree with the numerical predictions obtained via the Navier–Stokes equations. Conversely, for an orifice with a diameter of 50 µm or less, it is found that the thrust is lower than that predicted and the existence of jet swell becomes apparent. With the estimated elastic stress proportional to squared mean velocity, a change in the elasticity of the water as it flows through a micro-orifice is strongly suggested. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000008 [...]

Modeling and measurement of the dynamic surface tension of surfactant solutions / Tomiichi Hasegawa in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 8 (Août 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 8 (Août 2008) . - 8 p. Titre : Modeling and measurement of the dynamic surface tension of surfactant solutions Type de document : texte imprimé Auteurs : Tomiichi Hasegawa, Auteur ; Masahiro Karasawa, Auteur ; Takatsune Narumi, Auteur Année de publication : 2009 Article en page(s) : 8 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Surface  tension;  equilibrium  (physics);  surfactants;  water;  modeling Résumé : Surfactant solutions are usually used under conditions accompanied by transient dynamic surfaces, and therefore the dynamic surface tension (DST) is important in many industrial processes. Theories regarding DST have been developed exclusively on the adsorption theory that molecules are transported from bulk solution to the interface. However, the adsorption theory is not closed and requires another relationship between the interfacial concentration of the adsorbing molecules and the bulk concentration of molecules near and at the surface, which at present is based on assumptions. In addition, DST obtained by the adsorption theory contains several parameters that must be determined beforehand, and it is not simple to use for practical purposes. Here, we propose a new model based on the concept that surfactant molecules rotate during the process reaching the equilibrium surface state, which is different from the conventional adsorption theory, and we obtained a simple expression of DST as a function of the surface age. In addition, an experiment was carried out to determine DST by measuring the period and weight of droplets falling from a capillary. The expression by the proposed model was compared with the results of this experiment and with those reported previously by several other authors, and good agreement was obtained. Furthermore, the characteristic time in the model was shown to be correlated with the concentrations of solutions regardless of the type of solutions examined. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27329 [...] [article] Modeling and measurement of the dynamic surface tension of surfactant solutions [texte imprimé] / Tomiichi Hasegawa, Auteur ; Masahiro Karasawa, Auteur ; Takatsune Narumi, Auteur . - 2009 . - 8 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 8 (Août 2008) . - 8 p. Mots-clés : Surface  tension;  equilibrium  (physics);  surfactants;  water;  modeling Résumé : Surfactant solutions are usually used under conditions accompanied by transient dynamic surfaces, and therefore the dynamic surface tension (DST) is important in many industrial processes. Theories regarding DST have been developed exclusively on the adsorption theory that molecules are transported from bulk solution to the interface. However, the adsorption theory is not closed and requires another relationship between the interfacial concentration of the adsorbing molecules and the bulk concentration of molecules near and at the surface, which at present is based on assumptions. In addition, DST obtained by the adsorption theory contains several parameters that must be determined beforehand, and it is not simple to use for practical purposes. Here, we propose a new model based on the concept that surfactant molecules rotate during the process reaching the equilibrium surface state, which is different from the conventional adsorption theory, and we obtained a simple expression of DST as a function of the surface age. In addition, an experiment was carried out to determine DST by measuring the period and weight of droplets falling from a capillary. The expression by the proposed model was compared with the results of this experiment and with those reported previously by several other authors, and good agreement was obtained. Furthermore, the characteristic time in the model was shown to be correlated with the concentrations of solutions regardless of the type of solutions examined. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27329 [...]