Frederic Chalot

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.

LES and DES Simulations for Aircraft Design

The paper first describes developments performed to achieve an accurate and efficient simulation capacity using turbulence models based on the LES and DES approaches. The development is performed within the industrial code used at Dassault for the aerodynamics design of both military aircraft and business jets. The issues of subgrid scale implementation and wall treatment approaches are addressed. The paper then presents industrial applications performed at Dassault related to aerodynamic design. Examples demonstrate the impact of LES and DES on key design issues where complex flow features are present.

Higher-Order Stabilized Finite Elements in an Industrial Navier-Stokes Code

This chapter covers Dassault Aviation’s contribution to Workpackage 3 of the ADIGMA Project, which focuses on the extension of its stabilized finite element industrial Navier-Stokes code to higher-order elements. Mesh generation aspects are treated and especially the issue of highly-stretched curved elements close to the wall boundary of Navier-Stokes meshes. The high-order approach is carefully assessed using inviscid subsonic and transonic, laminar, and high Reynolds number turbulent flows.

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.

Higher-Order RANS and DES in an Industrial Stabilized Finite Element Code

This chapter describes the contribution of Dassault Aviation to the IDIHOM Project. It focuses on the extension of its stabilized finite element Navier-Stokes code to higher-order elements and more specifically on industrial RANS and DES applications.

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.

SOLVING LINEAR SYSTEMS WITH MULTIPLE RIGHT-HAND SIDES WITH GMRES : AN APPLICATION TO AIRCRAFT DESIGN

To create efficient new aerodynamic designs or predict the onset of flutter, the linearised Navier-Stokes equations might be used. In some cases, many right-hand sides must be solved keeping the same matrix. In this paper, techniques which enable to solve several righthand sides at the same time, such as Block GMRes, or reuse pieces of information computed in the previous solves, such as Krylov space recycling, are investigated. They will be tested on both simple and industrial test cases.

Goal-Oriented Mesh Adaptation in an Industrial Stabilized Finite Element Navier-Stokes Code

This chapter describes Dassault Aviation’s contribution to Workpackage 5 of the ADIGMA Project. The adjoint operator developed in the framework of optimum design is used to estimate the error in the solution with respect to a given target quantity. Local values of this error estimation are used as a criterion to refine the mesh. This yields significant improvement over traditional criteria based on the residual or on gradients of physical quantities. The method is carefully tested using inviscid, transonic, laminar, and high Reynolds number turbulent flows.