Le problème de Helmoltz pour des obstacles peu réguliers

The classical Helmholtz model for wakes behind an obstacle in perfect fluid mechanics boils down in complex analysis into a Riemann problem with free boundary, the free boundary being the wake and being such that the Riemann map parametrizes it as arclength parametrization. We generalize a method due to Coifman and Meyer [CM] to solve this problem for a class of non-smooth obstacles

Le problème de Helmoltz pour des obstacles peu réguliers

The classical Helmholtz model for wakes behind an obstacle in perfect fluid mechanics boils down in complex analysis into a Riemann problem with free boundary, the free boundary being the wake and being such that the Riemann map parametrizes it as arclength parametrization. We generalize a method due to Coifman and Meyer [CM] to solve this problem for a class of non-smooth obstacles

Temperature measurement using infrared thermography of the dielectric in a DBD plasma actuator dedicated to subsonic airflow control

Présentation oral

Effets de l'alimentation protéiprive à court terme sur la sécrétion d'azote endogène : sécrétion pancréatique exocrine chez le porc

International audienc

Experimental study of the flow induced by a sinusoidal Dielectric Barrier Discharge actuator and ist effects on a flate natural boundary layer

International audienceSince the mid-1990s, electrohydrodynamic actuators have been developed for modifying on subsonic airflows. The principle of plasma action is the use of the direct conversion of electrical energy into kinetic energy in order to act on the flow boundary layer. This paper presents our contribution to such an investigation concerning an electrohydrodynamic actuator consisting of several sinusoidal dielectric barrier discharges. First, the ionic wind induced by this actuator was measured with a pressure sensing probe. The induced flow velocity increased with the applied voltage and frequency. The particle image velocimetry system without external airflow showed the presence of induced swirls, generated by the ion movement in plasma. Then the action of this actuator on a flat plate boundary layer in parallel flow at zero incidence was studied in a subsonic wind tunnel. Experiments were performed for 15 m/s and 22 m/s. They showed that electric discharges (8 kV, 1 kHz) acting on a laminar flow tripped the laminar-to-turbulent transition. Moreover, higher applied voltages (up to 12 kV, 1 kHz) were necessary for modifying turbulent boundary layers