Dassault Aviation

About: Dassault Aviation is a company organization based out in Paris, France. It is known for research contribution in the topics: Finite element method & Aerodynamics. The organization has 564 authors who have published 645 publications receiving 11000 citations. The organization is also known as: Dassault.

Drag reduction by active control for flow past cylinders

Abstract: The main objective of this article is to investigate computational methods for the active control and drag optimization of incompressible viscous flow past cylinders, using the two-dimensional Navier-Stokes equations as the flow model. The computational methodology relies on the following ingredients: space discretization of the Navier-Stokes equations by finite element approximations, time discretization by a second order accurate two step implicit/explicit finite difference scheme, calculation of the cost function gradient by the adjoint equation approach, minimization of the cost function by a quasi-Newton method a la BFGS. The above methods have been applied to predict the optimal forcing-control strategies in reducing drag for flow around a circular cylinder using either an oscillatory rotation or blowing and suction. In the case of oscillatory forcing, a drag reduction of 31% at Reynolds number 200 and 61% at Reynolds number 1000 was demonstrated. Using only three blowing-suction slots, we have been able to completely suppress the formation of the Von-Karman vortex street up to Reynolds number 200 with a significant net drag reduction. We conclude this article by an appendix describing a bisection method which allows very substantial storage memory savings at reasonable extra computational time when applying adjoint equation based methodologies to the solution of control problems modeled by time dependent equations.

Aircraft airfoil leading edge member equipped with a de-icing device

Abstract: A leading edge member (1a) of an airfoil (V) of an aircraft has an outside wall (5a) and a de-icing device of the type for circulating hot air in the direction of the span of said airfoil. Said device includes a) a hot air distribution duct (15a) extending inside said leading edge member in said direction and having a plurality of orifices (25a) distributed over at least part of its length, and b) hot air supply means (19a) communicating with one end (17a) of said distribution duct (15a; 15b). Said hot air supply means (19a) are adapted to be connected by ducts (C) located outside said leading edge member to at least one propulsion engine (M) of said aircraft.

A tetrahedral-based superconvergent scheme for aeroacoustics

Abstract: We describe a numerical scheme for hyperbolics well adapted to both aerodynamics and aeroacoustics. The scheme is vertex centered, It applies with second order accuracy to unstructured tetrahedrizations and extends to higher order (up to sixth) on a certain type of cartesian meshes. Several basic aeroacoustic numerical experiments are presented.

Device for assisting aircraft crew when performing flight level changes

Abstract: This device providing assistance to aircraft crew for a flight level change of the aircraft in air traffic, comprising means for viewing the position of the aircraft in the vertical plane, is wherein the viewing means comprise: display means capable of displaying an image comprising at least one zone corresponding to a target altitude (FL) for the aircraft, and in that it comprises: selection means for selecting said zone in the image.

Preparation and Microwave Properties of Silica Coated Ni–Fe–Mo Flakes Composites

Abstract: Fabrication of silica coated permalloy-like flaky particles and microwave properties of uncoated and coated particles dispersed in a polymer matrix are presented. The silica layer is successfully obtained through the Stober process and its thickness is about 50 nm. Permeability and permittivity measurements are carried out using an APC7 coaxial line. It is demonstrated that composites with an insulating layer exhibit the same permeability levels as the ones filled with uncoated permalloy-like flakes but lower permittivity levels which improves its impedance matching and thus enhances its microwave absorbing properties. Calculated reflection loss of 1 mm composite layer shows that peak frequencies are shifted to higher frequencies while their intensities are slightly increased when composites are filled with coated flaky particles (-4.26 dB at 1.89 GHz for the uncoated flakes and -4.53 dB at 2.57 GHz for the coated ones at the same volume content of 21%). Composites filled with higher volume contents are expected to be promising candidates as absorbing materials above the GHz range.