Documents disponibles écrits par cet auteur

Active control of flow separation in a radial blower / Greenblatt, David in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 5 (Mai 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 5 (Mai 2010) . - 06 p. Titre : Active control of flow separation in a radial blower Type de document : texte imprimé Auteurs : Greenblatt, David, Auteur ; Guy Arzuan, Auteur Année de publication : 2010 Article en page(s) : 06 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : pressure;  separation  (technology);  acoustics;  Reynolds  number;  impellers;  flow  visualization;  shear  (mechanics);  actuators;  blades;  flat  plates;  flow  separation;  frequency;  airfoils Résumé : An experimental investigation was undertaken as a proof-of-concept study for active separation control in a radial blower. Acoustic perturbations were introduced into the impeller housing of a small radial blower with fully stalled blades. Increases in the plenum pressure of 35% were achieved and, based on tuft-based flow visualization, it was concluded that the pressure increases were brought about due to excitation and deflection of the leading-edge separated shear layer. Within the parameter range considered here, the optimum dimensionless control frequencies were found to be O(0.5), irrespective of the blade orientation or number of blades. Moreover, the maximum pressure rise was achieved with an investment of only 2% of the fan input power. Backward bladed impeller blades exhibited slightly larger increases in pressure coefficients when compared with their forward bladed counterparts. The dependence of blower performance on reduced frequency was remarkably similar to that seen on flat plate airfoils at similar Reynolds numbers under periodic excitation. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27418 [...] [article] Active control of flow separation in a radial blower [texte imprimé] / Greenblatt, David, Auteur ; Guy Arzuan, Auteur . - 2010 . - 06 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 5 (Mai 2010) . - 06 p. Mots-clés : pressure;  separation  (technology);  acoustics;  Reynolds  number;  impellers;  flow  visualization;  shear  (mechanics);  actuators;  blades;  flat  plates;  flow  separation;  frequency;  airfoils Résumé : An experimental investigation was undertaken as a proof-of-concept study for active separation control in a radial blower. Acoustic perturbations were introduced into the impeller housing of a small radial blower with fully stalled blades. Increases in the plenum pressure of 35% were achieved and, based on tuft-based flow visualization, it was concluded that the pressure increases were brought about due to excitation and deflection of the leading-edge separated shear layer. Within the parameter range considered here, the optimum dimensionless control frequencies were found to be O(0.5), irrespective of the blade orientation or number of blades. Moreover, the maximum pressure rise was achieved with an investment of only 2% of the fan input power. Backward bladed impeller blades exhibited slightly larger increases in pressure coefficients when compared with their forward bladed counterparts. The dependence of blower performance on reduced frequency was remarkably similar to that seen on flat plate airfoils at similar Reynolds numbers under periodic excitation. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27418 [...]

Application of large gurney flaps on low reynolds number fan blades / Greenblatt, David in Transactions of the ASME . Journal of fluids engineering, Vol. 133 N° 2 (Fevrier 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 133 N° 2 (Fevrier 2011) . - 08 p. Titre : Application of large gurney flaps on low reynolds number fan blades Type de document : texte imprimé Auteurs : Greenblatt, David, Auteur Année de publication : 2011 Article en page(s) : 08 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Aerodynamics  Aerospace  components  Automotive  components  Blades  Drag  reduction  Fans Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : On the basis of a semi-empirical model, large Gurney flaps of 10%, 20%, and 30% of the fan blade chord length were tested in a specially designed ventilation fan facility. At the highest volumetric flowrates tested, the flapped blades all produced higher pressures than the baseline nonflapped case. When proper accounting was made of fan rotational speed, all flapped blades produced consistently higher dimensionless pressures, with the 30% flap producing the highest pressures at large volumetric flowrates. Based on the assumption that sound power varies with the sixth power of fan rotation speed, it was shown that the sound pressure level could be reduced by nearly 4 dB. All flapped configurations produced higher mechanical efficiency than the baseline case but the mass of the flap relative to that of the blade emerged as an important parameter. A 10% flap, whose mass was negligible relative to the blade, produced the largest increase of 18% in static efficiency. Further research will focus on testing the flaps over the entire operational range, as well as on redesigning stiffer and lighter Gurney flaps. The introduction of three-dimensionality such as spanwise spaced holes, slits, or serrations that have previously been used to reduce airfoil drag will also be considered. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA400013 [...] [article] Application of large gurney flaps on low reynolds number fan blades [texte imprimé] / Greenblatt, David, Auteur . - 2011 . - 08 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 133 N° 2 (Fevrier 2011) . - 08 p. Mots-clés : Aerodynamics  Aerospace  components  Automotive  components  Blades  Drag  reduction  Fans Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : On the basis of a semi-empirical model, large Gurney flaps of 10%, 20%, and 30% of the fan blade chord length were tested in a specially designed ventilation fan facility. At the highest volumetric flowrates tested, the flapped blades all produced higher pressures than the baseline nonflapped case. When proper accounting was made of fan rotational speed, all flapped blades produced consistently higher dimensionless pressures, with the 30% flap producing the highest pressures at large volumetric flowrates. Based on the assumption that sound power varies with the sixth power of fan rotation speed, it was shown that the sound pressure level could be reduced by nearly 4 dB. All flapped configurations produced higher mechanical efficiency than the baseline case but the mass of the flap relative to that of the blade emerged as an important parameter. A 10% flap, whose mass was negligible relative to the blade, produced the largest increase of 18% in static efficiency. Further research will focus on testing the flaps over the entire operational range, as well as on redesigning stiffer and lighter Gurney flaps. The introduction of three-dimensionality such as spanwise spaced holes, slits, or serrations that have previously been used to reduce airfoil drag will also be considered. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA400013 [...]