Documents disponibles écrits par cet auteur

Plasma-based flow-control strategies for transitional highly loaded low-pressure turbines / Donald P. Rizzetta in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 4 (Avril 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 4 (Avril 2008) . - 12 p. Titre : Plasma-based flow-control strategies for transitional highly loaded low-pressure turbines Type de document : texte imprimé Auteurs : Donald P. Rizzetta, Auteur ; Miguel R. Visbal, Auteur Année de publication : 2009 Article en page(s) : 12 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Plasma-based  active  flow  control;  low-pressure  turbines;  Navier–Stokes  equations;  numerical  method Résumé : Recent numerical simulations have indicated the potential of plasma-based active flow control for improving the efficiency of highly loaded low-pressure turbines. The configuration considered in the current and earlier simulations correspond to previous experiments and computations for the flow at a Reynolds number of 25,000 based on axial chord and inlet conditions. In this situation, massive separation occurs on the suction surface of each blade due to uncovered turning, causing blockage in the flow passage. It was numerically demonstrated that asymmetric dielectric-barrier-discharge actuators were able to mitigate separation, thereby decreasing turbine wake losses. The present investigation extends this work by investigating a number of plasma-based flow control strategies. These include the chordwise location of actuation, spanwise periodic arrays of actuators, multiple actuation in the streamwise direction, and spanwise-direct actuation. The effect of alternate plasma-force models is also considered. Solutions were obtained to the Navier–Stokes equations, which were augmented by source terms used to represent plasma-induced body forces imparted by an actuator on the fluid. The numerical method utilized a high-fidelity time-implicit scheme, employing domain decomposition to carry out calculations on a parallel computing platform. A high-order overset grid approach preserved spatial accuracy in locally refined embedded regions. Features of the flowfields are described, and resultant solutions are compared to each other, with a previously obtained control case, and with the base line situation where no control was enforced. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27307 [...] [article] Plasma-based flow-control strategies for transitional highly loaded low-pressure turbines [texte imprimé] / Donald P. Rizzetta, Auteur ; Miguel R. Visbal, Auteur . - 2009 . - 12 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 4 (Avril 2008) . - 12 p. Mots-clés : Plasma-based  active  flow  control;  low-pressure  turbines;  Navier–Stokes  equations;  numerical  method Résumé : Recent numerical simulations have indicated the potential of plasma-based active flow control for improving the efficiency of highly loaded low-pressure turbines. The configuration considered in the current and earlier simulations correspond to previous experiments and computations for the flow at a Reynolds number of 25,000 based on axial chord and inlet conditions. In this situation, massive separation occurs on the suction surface of each blade due to uncovered turning, causing blockage in the flow passage. It was numerically demonstrated that asymmetric dielectric-barrier-discharge actuators were able to mitigate separation, thereby decreasing turbine wake losses. The present investigation extends this work by investigating a number of plasma-based flow control strategies. These include the chordwise location of actuation, spanwise periodic arrays of actuators, multiple actuation in the streamwise direction, and spanwise-direct actuation. The effect of alternate plasma-force models is also considered. Solutions were obtained to the Navier–Stokes equations, which were augmented by source terms used to represent plasma-induced body forces imparted by an actuator on the fluid. The numerical method utilized a high-fidelity time-implicit scheme, employing domain decomposition to carry out calculations on a parallel computing platform. A high-order overset grid approach preserved spatial accuracy in locally refined embedded regions. Features of the flowfields are described, and resultant solutions are compared to each other, with a previously obtained control case, and with the base line situation where no control was enforced. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27307 [...]

Plasma control for a maneuvering low-aspect-ratio wing at low Reynolds number / Donald P. Rizzetta in Transactions of the ASME . Journal of fluids engineering, Vol. 134 N° 12 (Décembre 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 12 (Décembre 2012) . - 19 p. Titre : Plasma control for a maneuvering low-aspect-ratio wing at low Reynolds number Type de document : texte imprimé Auteurs : Donald P. Rizzetta, Auteur ; Miguel R. Visbal, Auteur Année de publication : 2013 Article en page(s) : 19 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : force;  flow  (dynamics);  aerodynamics;  fluids;  motion;  eddies  (fluid  dynamics);  Reynolds  number;  plasmas  (ionized  gases);  plasma  confinement;  chords  (trusses);  actuators;  computation;  wings Résumé : Plasma-based flow control was explored as a means of enhancing the performance of a maneuvering flat-plate wing. For this purpose, a numerical investigation was conducted via large-eddy simulation (LES). The wing has a rectangular planform, a thickness to chord ratio of 0.016, and an aspect ratio of 2.0. Computations were carried out at a chord-based Reynolds number of 20,000, such that the configuration and flow conditions are typical of those commonly utilized in a small unmanned air system (UAS). Solutions were obtained to the Navier–Stokes equations, that were augmented by source terms used to represent body forces imparted by plasma actuators on the fluid. A simple phenomenological model provided these body forces resulting from the electric field generated by the plasma. The numerical method is based upon a high-fidelity time-implicit scheme and an implicit LES approach, which were applied to obtain solutions on an overset mesh system. Specific maneuvers considered in the investigation all began at 0 deg angle of attack, and consisted of a pitch-up and return, a pitch-up and hold, and a pitch-up to 60 deg. The maximum angle of attack for the first two maneuvers was 35 deg, which is well above that for static stall. Two different pitch rates were imposed for each of the specified motions. In control situations, a plasma actuator was distributed in the spanwise direction along the wing leading edge, or extended in the chordwise direction along the wing tip. Control solutions were compared with baseline results without actuation in order to assess the benefits of flow control and to determine its effectiveness. In all cases, it was found that plasma control can appreciably improve the time integrated lift over the duration of the maneuvers. The wing-tip actuator could achieve up to a 40% increase in the integrated lift, above that of the baseline value. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Plasma control for a maneuvering low-aspect-ratio wing at low Reynolds number [texte imprimé] / Donald P. Rizzetta, Auteur ; Miguel R. Visbal, Auteur . - 2013 . - 19 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 12 (Décembre 2012) . - 19 p. Mots-clés : force;  flow  (dynamics);  aerodynamics;  fluids;  motion;  eddies  (fluid  dynamics);  Reynolds  number;  plasmas  (ionized  gases);  plasma  confinement;  chords  (trusses);  actuators;  computation;  wings Résumé : Plasma-based flow control was explored as a means of enhancing the performance of a maneuvering flat-plate wing. For this purpose, a numerical investigation was conducted via large-eddy simulation (LES). The wing has a rectangular planform, a thickness to chord ratio of 0.016, and an aspect ratio of 2.0. Computations were carried out at a chord-based Reynolds number of 20,000, such that the configuration and flow conditions are typical of those commonly utilized in a small unmanned air system (UAS). Solutions were obtained to the Navier–Stokes equations, that were augmented by source terms used to represent body forces imparted by plasma actuators on the fluid. A simple phenomenological model provided these body forces resulting from the electric field generated by the plasma. The numerical method is based upon a high-fidelity time-implicit scheme and an implicit LES approach, which were applied to obtain solutions on an overset mesh system. Specific maneuvers considered in the investigation all began at 0 deg angle of attack, and consisted of a pitch-up and return, a pitch-up and hold, and a pitch-up to 60 deg. The maximum angle of attack for the first two maneuvers was 35 deg, which is well above that for static stall. Two different pitch rates were imposed for each of the specified motions. In control situations, a plasma actuator was distributed in the spanwise direction along the wing leading edge, or extended in the chordwise direction along the wing tip. Control solutions were compared with baseline results without actuation in order to assess the benefits of flow control and to determine its effectiveness. In all cases, it was found that plasma control can appreciably improve the time integrated lift over the duration of the maneuvers. The wing-tip actuator could achieve up to a 40% increase in the integrated lift, above that of the baseline value. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]