Fifth Drag Prediction Workshop: Computational Fluid Dynamics Studies Carried Out at ONERA

Abstract

This article presents the computational studies which have been performed at ONERA in the context of the 5 th AIAA Drag Prediction Workshop (DPW-5). A grid convergence process and a buffet onset study have been carried out using a Reynolds-averaged Navier-Stokes (RANS) solver and far-field methods. In this work, the Multi-Block (MB) grids of the Common Research Model (CRM) provided by the DPW-5 Committee are employed and a new meshing strategy involving overset techniques and Cartesian grids is tested. All these meshes are computed with the ONERA-elsA code using the Spalart-Allmaras turbulence model and far-field drag analyses are performed with the ONERA-ffd72 software. The grid convergence study led with the Common MB grids gives an extrapolated drag value close to 250 drag counts, which corresponds to the numerical median of all DPW-5 participants. The meshing approach using Cartesian grids also provides promising results. Comparisons with NASA wind tunnel tests show reasonable discrepancies between Computational Fluid Dynamics (CFD) predictions and experimental drag measurements. The buffet onset study completed with the medium Common MB grid is aimed at investigating an angle of attack sweep at cruise Mach number. Global and local analyses combining near-field and far-field approaches are presented.

Validation of a near-body and off-body grid partitioning methodology for aircraft aerodynamic performance prediction

“…These structured grids have produced consistent results and relatively good agreement with the National Transonic Facility (NTF) experimental data [25]. The different characteristics of these meshes are indicated in Table 1.…”

“…3. If the expected accuracy for drag prediction is below the count (1 drag count = 0.0001 CD, where CD is the drag coefficient), the grid convergence study shown in [25] has indicated that the fourth refinement level (L4/17 million elements) is sufficient to evaluate the aerodynamic coefficients correctly.…”

“…Finally, the closest reference data that can be used for this paper corresponds to the numerical results obtained with the DPW-5 common grids described above. Some of these outcomes are presented in [25], they include near-field and far-field components. Since the grid converged value of drag obtained by ONERA is very close to the CFD median of all DPW-5 participants [30], i.e.…”

“…All the near-body grids presented here are basic O-type grids but C-type grids can be done as well. As it has been proved as sufficient [25], the refinement of the mesh L4 has been used as an example for the surface grids which are shown below.…”

“…The CRM is an open geometry representative of current wide-body commercial aircraft [23], for which a wealth of experimental and numerical data is available. This configuration has been deeply studied at ONERA [24][25][26] in the framework of DPW-4 (San Antonio, 2009) and DPW-5 (New Orleans, 2012) which was focused on a deep grid convergence study.…”