Three-dimensional CFD simulations with large displacement of the geometries using a connectivity-change moving mesh approach

This paper deals with three-dimensional (3D) numerical simulations involving 3D moving geometries with large displacements on unstructured meshes. Such simulations are of great value to industry, but remain very time-consuming. A robust moving mesh algorithm coupling an elasticity-like mesh deformation solution and mesh optimizations was proposed in previous works, which removes the need for global remeshing when performing large displacements. The optimizations, and in particular generalized edge/face swapping, preserve the initial quality of the mesh throughout the simulation. We propose to integrate an Arbitrary Lagrangian Eulerian compressible flow solver into this process to demonstrate its capabilities in a full CFD computation context. This solver relies on a local enforcement of the discrete geometric conservation law to preserve the order of accuracy of the time integration. The displacement of the geometries is either imposed, or driven by fluid–structure interaction (FSI). In the latter case, the six degrees of freedom approach for rigid bodies is considered. Finally, several 3D imposed-motion and FSI examples are given to validate the proposed approach, both in academic and industrial configurations

Towards goal-oriented mesh adaptation for fluid-structure interaction

In order to address fluid-structure interaction, we present an a priori analysis for an ALE compressible flow model. This analysis is the key for an anisotropic metricbased mesh adaptation

Connectivity-change moving mesh methods for high-order meshes: Toward closed advancing-layer high-order boundary layer mesh generation

International audienceCurved mesh generation starting from a P1 mesh and closed advancing-layer boundary layer mesh generation both rely on mesh deformation and mesh optimization techniques. The approach presented in this work is to generalize connectivity-change moving mesh methods to high-order meshes. This approach is based on a high-order linear elasticity solver for the mesh deformation and on high-order mesh optimization operators such as mesh smoothing and generalized swapping. Thanks to this method, Pk meshes are generated from P1 meshes and closed advancing-layer boundary layer mesh generation will soon be possible

P2 mesh optimization operators

International audienceCurved mesh generation starting from a P1 mesh relies on mesh deformation and mesh optimization techniques. Mesh optimization techniques consist in locally modifying the mesh in order to improve it with respect to a given quality criterion. This work presents the generalization of two mesh quality-based optimization operators to P2 meshes. The generalized operators consist in mesh smoothing and generalized swapping. With the use of these operators, P2 mesh generation starting from a P1 mesh is more robust and P2 connectivity-change moving mesh methods for large displacements are now possible

Grid-Adapted FUN3D Computations for the Second High Lift Prediction Workshop

Contributions of the unstructured Reynolds-averaged Navier-Stokes code FUN3D to the 2nd AIAA CFD High Lift Prediction Workshop are described, and detailed comparisons are made with experimental data. Using workshop-supplied grids, results for the clean wing configuration are compared with results from the structured code CFL3D Using the same turbulence model, both codes compare reasonably well in terms of total forces and moments, and the maximum lift is similarly over-predicted for both codes compared to experiment. By including more representative geometry features such as slat and flap brackets and slat pressure tube bundles, FUN3D captures the general effects of the Reynolds number variation, but under-predicts maximum lift on workshop-supplied grids in comparison with the experimental data, due to excessive separation. However, when output-based, off-body grid adaptation in FUN3D is employed, results improve considerably. In particular, when the geometry includes both brackets and the pressure tube bundles, grid adaptation results in a more accurate prediction of lift near stall in comparison with the wind-tunnel data. Furthermore, a rotation-corrected turbulence model shows improved pressure predictions on the outboard span when using adapted grids

Adaptive sonic boom sensitivity analysis

This paper presents an accurate approach to simulate the sonic boom of a supersonic aircraft. The near field flow is modeled by the conservative Euler equations and is solved using a finite volume approach on adapted unstructured tetrahedral meshes. Then, from the CFD solution, the pressure distribution under the aircraft is extracted and used to set up the initial conditions of the propagation algorithm in the far field. The pressure distribution is propagated down to the ground in order to obtain the sonic boom signature using a ray tracing algorithm based upon the Thomas waveform parameter method. In this study, a sonic boom sensitivity analysis on the SSBJ geometry provided by Dassault Aviation is carried out

High Order Sonic Boom Modeling by Adaptive Methods

International audienceThis paper presents an accurate approach to simulate the sonic boom of supersonic aircrafts. The near-field flow is modeled by the conservative Euler equations and is solved using a vertex-centered finite volume approach on adapted unstructured tetrahedral meshes. A metric-based anisotropic mesh adaptation is considered to control the interpolation error in Lp norm. Then, from the CFD solution, the pressure distribution under the aircraft is extracted and used to set up the initial conditions of the propagation algorithm in the far-field. The pressure distribution is propagated down to the ground in order to obtain the sonic boom signature using a ray tracing algorithm based upon the Thomas waveform parameter method. In this study, a sonic boom sensitivity analysis is carried out on several aircraft designs (low-drag and low-boom shapes)