Michel Ravachol

A CONSISTENT FINITE ELEMENT APPROACH TO LARGE EDDY SIMULATION

This paper presents validation test cases of an LES solver based on an unstructured finite-element compressible Navier-Stokes code. After a short description of the industrial tool, we explain the incremental approach we have adopted in order to attain a reliable LES capability. Each step is illustrated by numerical examples and comparisons with experiments or theoretical results.

A Multi-platform Shared- or Distributed-Memory Navier-Stokes Code

Computational Fluid Dynamics (CFD) has always been an avid consumer of computing resources, and thus developed concurrently with the progresses in computer hardware. Born with the good old mainframes, CFD came to maturity with the vector architectures of the eighties (Cray, Convex, IBM, NEC). In 1992, VIRGINIE, the Navier–Stokes code in use at Dassault Aviation, was successfully ported onto the Intel IPSC 860 at ONERA. The first in-house massively parallel architecture dedicated to CFD was an IBM SPl, soon upgraded to an SP2. The high level of vectorization of Dassault–Aviations Navier–stokes code enabled performances in the 500 MFLOPS range. The implementations of VIRGINIE are described in this chapter on both the IBM SP2 and the NEC SX-4. The idea behind the SX-4 port was to keep the alterations to VIRGIN IE at their minimum and to use a code as close as possible to the SP2 version. Parallel computations are performed on a daily basis in the Aerodynamic Modelization Department at Dassault Aviation. A few civil and military applications are presented. The chapter also presents two parallel ports of the same vectorized finite-element Navier–stokes code onto two different parallel architectures, the IBM SP2 and the NEC SX-4. The SP2 is conceptually simpler since it implements a paradigm close to the idea of a finite element method. The unique drawback is that more effort must be deployed in order to split every new mesh into blocks.

Improvements of Upwind Formulations on Unstructured Meshes

In the framework of Euler solvers on unstructured meshes, a class of methods is based on an interpretation of a Galerkin formulation as a finite volume approximation on a dual mesh made of cells. In this paper, we propose a new definition for the dual cells, that may improve the accuracy and grid-insensitiveness for this methodology.

Status and Future Challenges of CFD in a Coupled Simulation Environment for Aircraft Design

The state of the art of Computational Fluid Dynamics and the axis of improvements are described. The issue of flutter prediction is addressed first: the use of linearized Euler solvers for transonic flutter is explained. Recent advances in optimum aerodynamic shape design are presented next, the results demonstrate the applicability of optimization based on the Euler equations and open the way to multidisciplinary optimum design. Finally, the use of Large Eddy Simulation for accurate turbulent flow simulation is illustrated.

Low boom airplane design process at Dassault Aviation

Dassault Aviation as a civil aircraft manufacturer is studying the feasibility of a supersonic business jet. One of the prerequisites for an environmentally friendly and economically viable supersonic aircraft is that its sonic boom signature is reduced to a level acceptable for flight over populated areas. The method presented here is part of the Dassault Aviation toolbox dedicated to the evaluation and/or to the design process of a low boom constrained supersonic aircraft.