Navegando por Autor "El Droubi, Ashraf"

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    Efeito da descarga de barreira dielétrica no escoamento do ar sobre um cilindro
    (Biblioteca Digital de Teses e Dissertações da USP, 2017-11-15) El Droubi, Ashraf
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    Investigation of the efficiency of a novel three electrode configuration for the dielectric barrier discharge
    (2018-10-11) El Droubi, Ashraf
    Having gained popularity in the last decade, the dielectric barrier discharge (DBD) has been studied in numerous ways as a device for air acceleration. A major interest of all these works has been concentrated on achieving higher efficiency and producing higher jet velocities. These studies considered alternative geometries, different voltage waveforms etc., yet none of these studies tackle the inherently inefficient process of force creation and actuation in a DBD. Air acceleration has been attributed to the electric force that switches direction on each voltage half cycle (that is due to the nature of the discharge mechanism) yet has a forward resulting force. The present thesis considers the phenomenon of memory charge accumulation on the dielectric surface and reasons that the backward force in the second half cycle can be reversed by further migration of the memory charges to an added exposed anode. Hence a novel 3-electrode configuration is presented. Flow velocity investigations showed a 27% improvement in efficiency in comparison with the traditional 2-electrode actuator. This meant a 0.4m/s gain along the velocity profile. During the investigation process, a new discharge mechanism was encountered. This was characterized by the double discharge lines along the exposed electrode edges while in the presence of a \"floating\" encapsulated electrode.