Documents disponibles écrits par cet auteur

Aerodynamic characteristics of asymmetric bluff bodies / J. C. Hu in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 1 (Janvier 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 1 (Janvier 2009) . - 09 p. Titre : Aerodynamic characteristics of asymmetric bluff bodies Type de document : texte imprimé Auteurs : J. C. Hu, Auteur ; Y. Zhou, Auteur Année de publication : 2009 Article en page(s) : 09 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : pressure;  flow  (dynamics);  aerodynamics;  fluids;  drag  (fluid  dynamics);  wakes;  corners  (structural  elements);  vortices;  cylinders;  vortex  shedding Résumé : The wake of asymmetric bluff bodies was experimentally measured using particle imaging velocimetry, laser Doppler anemometry, load cell, hotwire, and flow visualization techniques at Re=2600–8500 based on the freestream velocity and the characteristic height of the bluff bodies. Asymmetry is produced by rounding some corners of a square cylinder and leaving others unrounded. It is found that, with increasing corner radius, the flow reversal region is expanded, and the vortex formation length is prolonged. Accordingly, the vortex shedding frequency increases and the base pressure rises, resulting in a reduction in the mean drag as well as the fluctuating drag and lift. It is further found that, while the asymmetric cross section of the cylinder causes the wake centerline to shift toward the sharp corner side of the bluff body, the wake remains globally symmetric about the shifted centerline. The near wake of asymmetric bluff bodies is characterized in detail, including the Reynolds stresses, characteristic velocity, and length scale, and is further compared with that of the symmetric ones. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Aerodynamic characteristics of asymmetric bluff bodies [texte imprimé] / J. C. Hu, Auteur ; Y. Zhou, Auteur . - 2009 . - 09 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 1 (Janvier 2009) . - 09 p. Mots-clés : pressure;  flow  (dynamics);  aerodynamics;  fluids;  drag  (fluid  dynamics);  wakes;  corners  (structural  elements);  vortices;  cylinders;  vortex  shedding Résumé : The wake of asymmetric bluff bodies was experimentally measured using particle imaging velocimetry, laser Doppler anemometry, load cell, hotwire, and flow visualization techniques at Re=2600–8500 based on the freestream velocity and the characteristic height of the bluff bodies. Asymmetry is produced by rounding some corners of a square cylinder and leaving others unrounded. It is found that, with increasing corner radius, the flow reversal region is expanded, and the vortex formation length is prolonged. Accordingly, the vortex shedding frequency increases and the base pressure rises, resulting in a reduction in the mean drag as well as the fluctuating drag and lift. It is further found that, while the asymmetric cross section of the cylinder causes the wake centerline to shift toward the sharp corner side of the bluff body, the wake remains globally symmetric about the shifted centerline. The near wake of asymmetric bluff bodies is characterized in detail, including the Reynolds stresses, characteristic velocity, and length scale, and is further compared with that of the symmetric ones. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Numerical prediction of wind flow around irregular models / D. Y. Wang in Transactions of the ASME . Journal of fluids engineering, Vol. 134 N° 7 (Juillet 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 7 (Juillet 2012) . - 11 p. Titre : Numerical prediction of wind flow around irregular models Type de document : texte imprimé Auteurs : D. Y. Wang, Auteur ; Y. Zhou, Auteur ; Y. Zhu, Auteur Année de publication : 2012 Article en page(s) : 11 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : numerical  prediction;  large  Eddy  simulation;  irregular-plan  buildings;  computational  fluid  dynamics;  wind  pressure  coefficient;  wind  velocity  profile Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This paper presents numerical predictions of flow around irregular-plan buildings (S-, R-, L- and U-shaped models) in high Reynolds number. The adopted computational approach and numerical models are described firstly. Then comparative analysis with the numerical and experimental data has been conducted to verify the reliability of the numerical predictions. Finally, characteristics of mean and fluctuating pressure distributions and vertical and lateral velocity profiles of the flow around the four models have been investigated and assessed thoroughly. The study shows that satisfactory results can be obtained by large eddy simulation (LES), especially when fluctuating wind velocity is considered in the inflow boundary. Distribution of mean pressure coefficients on front faces is relatively regular. Large fluctuating pressure coefficients are induced by strong vortex motion. Velocity profiles of wind flow are disturbed obviously among the four building models, especially in weak flow. The disturbed intensity decreases with increasing of the distance away from bluff body. The suggested MDS (Maximum Disturbance Scopes) away from bluff body are generally 0.25H in inflow zones, 0.4H in roof zones, 0.5H in both side zones and 3H in weak zones. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000007 [...] [article] Numerical prediction of wind flow around irregular models [texte imprimé] / D. Y. Wang, Auteur ; Y. Zhou, Auteur ; Y. Zhu, Auteur . - 2012 . - 11 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 7 (Juillet 2012) . - 11 p. Mots-clés : numerical  prediction;  large  Eddy  simulation;  irregular-plan  buildings;  computational  fluid  dynamics;  wind  pressure  coefficient;  wind  velocity  profile Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This paper presents numerical predictions of flow around irregular-plan buildings (S-, R-, L- and U-shaped models) in high Reynolds number. The adopted computational approach and numerical models are described firstly. Then comparative analysis with the numerical and experimental data has been conducted to verify the reliability of the numerical predictions. Finally, characteristics of mean and fluctuating pressure distributions and vertical and lateral velocity profiles of the flow around the four models have been investigated and assessed thoroughly. The study shows that satisfactory results can be obtained by large eddy simulation (LES), especially when fluctuating wind velocity is considered in the inflow boundary. Distribution of mean pressure coefficients on front faces is relatively regular. Large fluctuating pressure coefficients are induced by strong vortex motion. Velocity profiles of wind flow are disturbed obviously among the four building models, especially in weak flow. The disturbed intensity decreases with increasing of the distance away from bluff body. The suggested MDS (Maximum Disturbance Scopes) away from bluff body are generally 0.25H in inflow zones, 0.4H in roof zones, 0.5H in both side zones and 3H in weak zones. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000007 [...]

Recent progress in nanofluids based on transformer oil: preparation and electrical insulation properties / Lv, Y. Z. in IEEE electrical insulation magazine, Vol. 30 N° 5 (Septembre-Octobre 2014) 

Public ISBD [article]  in IEEE electrical insulation magazine > Vol. 30 N° 5 (Septembre-Octobre 2014) . - pp. 23 - 32 Titre : Recent progress in nanofluids based on transformer oil: preparation and electrical insulation properties Type de document : texte imprimé Auteurs : Lv, Y. Z., Auteur ; Y. Zhou, Auteur ; Li, C. R., Auteur Année de publication : 2015 Article en page(s) : pp. 23 - 32 Note générale : Génie électrique Langues : Français (fre) Mots-clés : Electric  strength  Paper  Power  transformers  Reliability  Transformer  oil Résumé : Given the adoption of ultrahigh-voltage ac and dc power transmission, it is desirable to develop a new kind of oil-paper insulation system, with higher dielectric strength and smaller volume compared with conventional insulation systems, in order to reduce the volume and mass of high-voltage power transformers and improve their long-term operational reliability [1], [2]. Methods of improving the dielectric properties of the oil-paper insulation have therefore been widely investigated [3], [4]. The most influential factors affecting the performance of oil-paper insulation systems are the low dielectric strength of transformer oil and its degradation caused by water and other contaminants [5]. The dielectric strength of oil-paper insulation may be increased by filtering the oil in order to remove water and other contaminants [6]. However, further increase in the dielectric strength of the oil is required in order to achieve reduction of transformer volume and mass. En ligne : http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6882597&filter%3DAND% [...] [article] Recent progress in nanofluids based on transformer oil: preparation and electrical insulation properties [texte imprimé] / Lv, Y. Z., Auteur ; Y. Zhou, Auteur ; Li, C. R., Auteur . - 2015 . - pp. 23 - 32. Génie électrique Langues : Français (fre) in IEEE electrical insulation magazine > Vol. 30 N° 5 (Septembre-Octobre 2014) . - pp. 23 - 32 Mots-clés : Electric  strength  Paper  Power  transformers  Reliability  Transformer  oil Résumé : Given the adoption of ultrahigh-voltage ac and dc power transmission, it is desirable to develop a new kind of oil-paper insulation system, with higher dielectric strength and smaller volume compared with conventional insulation systems, in order to reduce the volume and mass of high-voltage power transformers and improve their long-term operational reliability [1], [2]. Methods of improving the dielectric properties of the oil-paper insulation have therefore been widely investigated [3], [4]. The most influential factors affecting the performance of oil-paper insulation systems are the low dielectric strength of transformer oil and its degradation caused by water and other contaminants [5]. The dielectric strength of oil-paper insulation may be increased by filtering the oil in order to remove water and other contaminants [6]. However, further increase in the dielectric strength of the oil is required in order to achieve reduction of transformer volume and mass. En ligne : http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6882597&filter%3DAND% [...]