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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Feedback control of flow separation using synthetic jets

Kim, Kihwan 12 April 2006 (has links)
The primary goal of this research is to assess the effect of synthetic jets on flow separation and provide a feedback control strategy for flow separation using synthetic jets. The feedback control synthesis is conducted based upon CFD simulation for a rounded backward-facing step. The results of the synthetic jet experiments on an airfoil showed that synthetic jets have the potential for controlling the degree of flow separation beyond delaying the onset of flow separation. In the simulation, while the jet is ejected slightly upstream from the separation point, the feedback pressure signal is acquired at a downstream wall point where the vortex is fully developed. Due to the uniqueness of synthetic jets, i.e. "zero-net-mass flux", the profile of synthetic jet velocity cannot be arbitrarily generated. The possible control variables are the magnitude or frequency of the oscillating jet velocity. Consequently, the fluidic system in simulation consists of the actuator model and the NARMAX (Nonlinear Auto Regressive Moving Average with eXogenous inputs) flow model. This system shows a strong nonlinear pressure response to the input jet frequency. Low-pass filtering of the pressure response, introduced for pressure recovery, facilitates a quasi-linear approximation of the system in the frequency domain using the describing function method. The low-pass filter effectively separates the pressure response into two frequency bands. The lower frequency band below the filter pass frequency includes the quasi-linear response targeted by the feedback control and the higher band above the filter stop frequency contains the attenuated higher harmonics, which are treated as nonlinear disturbances. This quasi-linear approximation is utilized to design a PI controller for the fluidic system including the synthetic jet. To ensure one-to-one correspondence of the jet frequency and the filtered pressure response, the upper bound of the jet frequency is set at the frequency of the maximum pressure. The response of the resulting closed loop feedback control system, comprised of a PI controller, low-pass filter, SJA model and NARMAX model, is shown to track the desired pressure command with an improvement in the transient response over the open-loop system.
72

L'art et l'eau à Lyon /

Gardes, Gilbert, January 1986 (has links)
Th. 3e cycle--Hist. de l'art--Lyon 2, 1975. / Bibliogr. p.405-470. Index.
73

Contrôle de décollement par fente pulsée ou générateurs de vortex fluides

Petit, Gabriel Kourta, Azeddine. January 2007 (has links)
Reproduction de : Thèse de doctorat : Dynamique des fluides : Toulouse, INPT : 2005. / Titre provenant de l'écran-titre. Bibliogr. 124 réf.
74

Modélisation et simulation des phénomènes d'ébullition et du transfert de chaleur dans la zone d'impact d'un jet sur une plaque chaude

Seiler-Marie, Nathalie. Simonin, Olivier. January 2008 (has links)
Reproduction de : Thèse de doctorat : Mécanique des fluides : Toulouse, INPT : 2004. / Titre provenant de l'écran-titre. Bibliogr. 184 réf.
75

Investigation of buoyancy effects on turbulant nonpremixed jet flames by using normal and low-gravity conditions

Idicheria, Cherian Alex, Clemens, Noel T., January 2003 (has links)
Thesis (Ph. D.)--University of Texas at Austin, 2003. / Supervisor: Noel T. Clemens. Vita. Includes bibliographical references. Also available from UMI.
76

Analysis of a curved buoyant jet in an enclosure using LES

Badeau, Allen E. January 1900 (has links)
Thesis (Ph. D.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains xxii, 177 p. : ill. (some col.) Includes abstract. Includes bibliographical references (p. 151-154) and index.
77

Visual studies of jets injected into a turbulent boundary layer.

Lee, Hoi-yuen, Louis, January 1977 (has links)
Thesis--Ph. D., University of Hong Kong, 1978. / Also availalbe in microfilm.
78

Flow structures of coaxial jets /

Au, Hom. January 1983 (has links)
Thesis--Ph. D., University of Hong Kong, 1984.
79

Effect of air jet in metal cutting /

Lau, Shing-pui, Alex. January 1985 (has links)
Thesis (M. Phil.)--University of Hong Kong, 1986.
80

Characterization of strongly forced non-premixed methane jet flames

Lakshminarasimhan, Krishna 28 August 2008 (has links)
Not available / text

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