Documents disponibles écrits par cet auteur

LES study of the influence of a train-nose shape on the flow structures under cross-wind conditions / Hassan Hemida in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 9 (Septembre 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 9 (Septembre 2008) . - 12 p. Titre : LES study of the influence of a train-nose shape on the flow structures under cross-wind conditions Type de document : texte imprimé Auteurs : Hassan Hemida, Auteur ; Siniša Krajnovic, Auteur Année de publication : 2009 Article en page(s) : 12 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Cross-wind  flows;  trains  nose  shape;  large-eddy  simulation;  Smagorinsky  model;  Reynolds  number Résumé : Cross-wind flows around two simplified high-speed trains with different nose shapes are studied using large-eddy simulation (LES) with the standard Smagorinsky model. The Reynolds number is 3×105 based on the height of the train and the freestream velocity. The cross section and the length of the two train models are identical while one model has a nose length twice that of the other. The three-dimensional effects of the nose on the flow structures in the wake and on the aerodynamic quantities such as lift and side force coefficients, flow patterns, local pressure coefficient, and wake frequencies are investigated. The short-nose train simulation shows highly unsteady and three-dimensional flow around the nose yielding more vortex structures in the wake. These structures result in a surface flow that differs from that in the long-nose train flow. They also influence the dominating frequencies that arise due to the shear-layer instabilities. Prediction of vortex shedding, flow patterns in the train surface, and time-averaged pressure distribution obtained from the long-nose train simulation are in good agreement with the available experimental data. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27337 [...] [article] LES study of the influence of a train-nose shape on the flow structures under cross-wind conditions [texte imprimé] / Hassan Hemida, Auteur ; Siniša Krajnovic, Auteur . - 2009 . - 12 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 9 (Septembre 2008) . - 12 p. Mots-clés : Cross-wind  flows;  trains  nose  shape;  large-eddy  simulation;  Smagorinsky  model;  Reynolds  number Résumé : Cross-wind flows around two simplified high-speed trains with different nose shapes are studied using large-eddy simulation (LES) with the standard Smagorinsky model. The Reynolds number is 3×105 based on the height of the train and the freestream velocity. The cross section and the length of the two train models are identical while one model has a nose length twice that of the other. The three-dimensional effects of the nose on the flow structures in the wake and on the aerodynamic quantities such as lift and side force coefficients, flow patterns, local pressure coefficient, and wake frequencies are investigated. The short-nose train simulation shows highly unsteady and three-dimensional flow around the nose yielding more vortex structures in the wake. These structures result in a surface flow that differs from that in the long-nose train flow. They also influence the dominating frequencies that arise due to the shear-layer instabilities. Prediction of vortex shedding, flow patterns in the train surface, and time-averaged pressure distribution obtained from the long-nose train simulation are in good agreement with the available experimental data. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27337 [...]

Transient simulation of the aerodynamic response of a double-deck bus in gusty winds / Hassan Hemida in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 3 (Mars 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 3 (Mars 2009) . - 10 p. Titre : Transient simulation of the aerodynamic response of a double-deck bus in gusty winds Type de document : texte imprimé Auteurs : Hassan Hemida, Auteur ; Siniša Krajnovic, Auteur Année de publication : 2009 Article en page(s) : 10 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : double  deck  bus;  aerodynamic  response;  Reynolds  number Résumé : The purpose of the research reported in this paper was to investigate the aerodynamic response of a double-deck bus in gusty winds using a detached-eddy simulation (DES). The bus was subjected to three different scenarios of wind gusts: gust in a wind tunnel, gust in a natural wind, and gust behind the exit of a tunnel. The proposed scenarios of gusts are in the time domain and take into account the dynamic behavior of natural winds. The Reynolds number of the flow, based on the time-averaged speed of the side wind and a reference length of 0.1 m, was 1.3×106. Detailed transient responses of the aerodynamic coefficients and flow structures were investigated. Good agreement was found between the DES results and the available experimental data. A comparison between the influence of the different gust scenarios on the aerodynamic coefficients shows that the gust behind the exit from a tunnel has a stronger influence on the aerodynamics than the other gust scenarios. Moreover, the influence of the gusts on the time history of aerodynamic coefficients is found to be limited to the period of the gust. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Transient simulation of the aerodynamic response of a double-deck bus in gusty winds [texte imprimé] / Hassan Hemida, Auteur ; Siniša Krajnovic, Auteur . - 2009 . - 10 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 3 (Mars 2009) . - 10 p. Mots-clés : double  deck  bus;  aerodynamic  response;  Reynolds  number Résumé : The purpose of the research reported in this paper was to investigate the aerodynamic response of a double-deck bus in gusty winds using a detached-eddy simulation (DES). The bus was subjected to three different scenarios of wind gusts: gust in a wind tunnel, gust in a natural wind, and gust behind the exit of a tunnel. The proposed scenarios of gusts are in the time domain and take into account the dynamic behavior of natural winds. The Reynolds number of the flow, based on the time-averaged speed of the side wind and a reference length of 0.1 m, was 1.3×106. Detailed transient responses of the aerodynamic coefficients and flow structures were investigated. Good agreement was found between the DES results and the available experimental data. A comparison between the influence of the different gust scenarios on the aerodynamic coefficients shows that the gust behind the exit from a tunnel has a stronger influence on the aerodynamics than the other gust scenarios. Moreover, the influence of the gusts on the time history of aerodynamic coefficients is found to be limited to the period of the gust. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]