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Analysis of coherent structures in the far-field region of an axisymmetric free jet identified using particle image velocimetry and proper orthogonal decomposition / A.-M. Shinneeb in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 1 (Janvier 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 1 (Janvier 2008) . - 9 p. Titre : Analysis of coherent structures in the far-field region of an axisymmetric free jet identified using particle image velocimetry and proper orthogonal decomposition Type de document : texte imprimé Auteurs : A.-M. Shinneeb, Auteur ; Balachandar, R., Auteur ; J. D. Bugg, Auteur Année de publication : 2009 Article en page(s) : 9 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Particulate  matter;  turbulence;  vortices;  principal  component  analysis;  flow  (dynamics);  water;  algorithms Résumé : This paper investigates an isothermal free water jet discharging horizontally from a circular nozzle (9mm) into a stationary body of water. The jet exit velocity was 2.5m∕s and the exit Reynolds number was 22,500. The large-scale structures in the far field were investigated by performing a proper orthogonal decomposition (POD) analysis of the velocity field obtained using a particle image velocimetry system. The number of modes used for the POD reconstruction of the velocity fields was selected to recover 40% of the turbulent kinetic energy. A vortex identification algorithm was then employed to quantify the size, circulation, and direction of rotation of the exposed vortices. A statistical analysis of the distribution of number, size, and strength of the identified vortices was carried out to explore the characteristics of the coherent structures. The results clearly reveal that a substantial number of vortical structures of both rotational directions exist in the far-field region of the jet. The number of vortices decreases in the axial direction, while their size increases. The mean circulation magnitude is preserved in the axial direction. The results also indicate that the circulation magnitude is directly proportional to the square of the vortex radius and the constant of proportionality is a function of the axial location. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Analysis of coherent structures in the far-field region of an axisymmetric free jet identified using particle image velocimetry and proper orthogonal decomposition [texte imprimé] / A.-M. Shinneeb, Auteur ; Balachandar, R., Auteur ; J. D. Bugg, Auteur . - 2009 . - 9 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 1 (Janvier 2008) . - 9 p. Mots-clés : Particulate  matter;  turbulence;  vortices;  principal  component  analysis;  flow  (dynamics);  water;  algorithms Résumé : This paper investigates an isothermal free water jet discharging horizontally from a circular nozzle (9mm) into a stationary body of water. The jet exit velocity was 2.5m∕s and the exit Reynolds number was 22,500. The large-scale structures in the far field were investigated by performing a proper orthogonal decomposition (POD) analysis of the velocity field obtained using a particle image velocimetry system. The number of modes used for the POD reconstruction of the velocity fields was selected to recover 40% of the turbulent kinetic energy. A vortex identification algorithm was then employed to quantify the size, circulation, and direction of rotation of the exposed vortices. A statistical analysis of the distribution of number, size, and strength of the identified vortices was carried out to explore the characteristics of the coherent structures. The results clearly reveal that a substantial number of vortical structures of both rotational directions exist in the far-field region of the jet. The number of vortices decreases in the axial direction, while their size increases. The mean circulation magnitude is preserved in the axial direction. The results also indicate that the circulation magnitude is directly proportional to the square of the vortex radius and the constant of proportionality is a function of the axial location. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]