Coupling mechanical rotation and EHD actuation in flow past a cylinder

The introduction of an electro-hydrodynamic (EHD) force in high performance numerical simulation may pose some problems as a consequence of the large differences between time or spatial scales of the physics of the discharge and those of interest for the fluid flow description. In this paper, we try to simplify this problem by looking for a correspondence between the global flow modifications produced by an EHD actuation and those by a moving body surface. Direct numerical simulations (DNS) of flow past a rotating cylinder are performed. For a flow regime corresponding to Reynolds number based on the cylinder diameter and free-stream velocity of the flow of 125 (wake-transition regime), the simulations allow us to make a comparison with particle image velocimetry (PIV) measures of the flow induced by a dielectric barrier discharge (DBD) plasma actuator suitably disposed on the cylinder surface. The results obtained from the projection of mean velocity fields show that the time-averaged vortical structures in the two cases enable us to establish a good analogy between actuations produced by both mechanisms.Fil: Gronskis, Alejandro. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: D’Adamo, J.. Universidad de Buenos Aires; ArgentinaFil: Artana, Guillermo Osvaldo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires; ArgentinaFil: Camillieri, A.. Universidad de Buenos Aires; ArgentinaFil: Silvestrini, J. H.. Pontificia Universidade Católica do Rio Grande do Sul; Brasi

Study of a pseudo-empirical model approach to characterize plasma actuators

The use of plasma actuators is a recent technology that imposes a localized electric force that is used to control air flows. A suitable representation of actuation enables to undertake plasma actuators optimization, to design flow-control strategies, or to analyse the flow stabilization that can be attained by plasma forcing. The problem description may be clearly separated in two regions. An outer region, where the fluid is electrically neutral, in which the flow is described by the Navier-Stokes equation without any forcing term. An inner region, that forms a thin boundary layer, where the fluid is ionized and electric forces are predominant. The outer limit of the inner solution becomes the boundary condition for the outer problem. The outer problem can then be solved with a slip velocity that is issued from the inner solution. Although the solution for the inner problem is quite complex it can be contoured proposing pseudo-empirical models where the slip velocity of the outer problem is determined indirectly from experiments. This pseudo-empirical model approach has been recently tested in different cylinder flows and revealed quite adapted to describe actuated flow behaviour. In this work we determine experimentally the influence of the duty cycle on the slip velocity distribution. The velocity was measured by means of a pitot tube and flow visualizations of the starting vortex (i.e. the induced flow when actuation is activated in a quiescent air) have been done by means of the Schlieren technique. We also performed numerical experiments to simulate the outer region problem when actuation is activated in a quiescent air using a slip velocity distribution as a boundary condition. The experimental and numerical results are in good agreement showing the potential of this pseudo-empirical model approach to characterize the plasma actuation.Fil:Grondona, D. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Márquez, A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Kelly, H. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina