2 résultat(s) recherche sur le tag 'flow''

Study of Causal Factors of Dark Circles Around the Eyes / Masayuki Matsumoto in IFSCC MAGAZINE, Vol. 4, N° 4 (10-11-12/2001)

[article]  inIFSCC MAGAZINE > Vol. 4, N° 4 (10-11-12/2001) . - p. 281-286 Titre : Study of Causal Factors of Dark Circles Around the Eyes Type de document : texte imprimé Auteurs : Masayuki Matsumoto, Auteur ; Noriko Kobayashi, Auteur ; Osamu Hoshina, Auteur ; Shoji Hayashi, Auteur ; Seiichi Arai, Auteur Année de publication : 2001 Article en page(s) : p. 281-286 Note générale : Bibliogr. Langues : Anglais (eng) Tags : 'Dark  circles'  Eyelid  'Internal  canthus'  'Blood  flow'  'Laser  Doppler  flowmeter'  'Skin  color'  lightness  (L*)'  surface  temperature' Index. décimale : 668.5 Parfums et cosmétiques Résumé : The characteristics of the dark circles were investigated using a laser Doppler flowmeter (LDF) and a chromameter. Regarding the blood flow, we found that the areas surrounding the internal canthus where the dark circles are frequently observed had larger blood mass and slower blood flow velocity compared to the other regions. Furthermore, this tendency is particularly evident in the superficial layers of the skin, and also in the lower part and the lateral part of the internal canthus. Our results suggest that naturally the blood flow in the areas surrounding the internal canthus tends to stagnate easily. Concerning the skin color, we found that the areas around the internal canthus tend to appear, particularly the skin color under the internal canthus had a low lightness (L*) value. There was a significant correlation between the differences in the blood mass (ΔMass) and the differences in lightness (ΔL*) in the lower part of the internal canthus and its adjacent regions. Furtheremore, compared to the person with less prominent dark circles, the person with prominent circles had larger differences between the lower part of the internal canthus and its adjacent regions in terms of the blood mass as well as the lightness. From our results, we concluded that retention of blood in the surface of the skin is a significant factor in the development of dark circles around the eyes. Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=10697 [article]

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Transient aspects of the polymer induces drag reduction phenomenon / Anselmo S. Pereira in RHEOLOGIE, Vol. 32 (12/2017)

[article]  inRHEOLOGIE > Vol. 32 (12/2017) . - n. p. Titre : Transient aspects of the polymer induces drag reduction phenomenon Type de document : texte imprimé Auteurs : Anselmo S. Pereira, Auteur Année de publication : 2018 Article en page(s) : n. p. Note générale : Thèse accessible en ligne - Bibliogr. Langues : Anglais (eng) Catégories : Analyse numérique Polymères Rhéologie Tags : 'Direct  numerical  simulation'  'T  turbulent  flow'  'FENE-P  model'  'Réduction  de  la  traînée'  'Transitory  aspects'  'Polymer  degradation' Index. décimale : 532.05 Mécanique des fluides et des liquides - Dynamique (cinétique et cinématique) Résumé : The addition of a small amount of polymers of high molecular weight can lead to a pressure drop decrease in turbulent flows. The polymers successively stretch and coil by interacting with the turbulent structures, which imposes a transient behaviour on the drag reduction (DR). As a result, DR undergoes three stages over time: A, B, and C. In stage A, DR departs from zero and assumes negative values due to a significant polymer stretching at the beginning of the process, which requires energy from the flow. After the minimum DR is reached, the polymers start their coil-stretch cycle and DR increases in response to the development of turbulent structures, achieving a maximum value, which makes for the beginning of stage B. However, during their coil-stretch cycle, polymers can be mechanically degraded as a result of an intense polymer stretching, which reduces their ability to act as energy exchange agents. Hence, when polymer degradation becomes pronounced, DR decreases until achieving a final value. The polymer degradation process characterizes the stage C. In the present work, numerical analyses are conducted aiming to investigate the stages A, B and C. The transient aspects of the polymer induced drag reduction phenomenon are explored with the aid of direct numerical simulations of turbulent plane Poiseulle and Couette flows of viscoelastic FENE-P fluids taking into account a large range of Reynolds number, Weissenberg number and maximum polymer molecule extensibility. Stages A and B are carefully studied from tensor, energy budget and spectral perspectives. A polymer scission model is developed in order to numerically reproduce the stage C. Note de contenu : - INTRODUCTION AND METHODOLOGY - RESULTS : The development of DR-Stage A - The DR mechanism-Stage B - The polymer degradation-Stage C Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=29773 [article]

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