Quantifying Uncertainty in Computational Fluid Dynamics Drag Computations on Unstructured Meshes

The present Paper investigates drag dispersion in computational fluid dynamics computations due to variations in the discretization domain. The application addresses typical aeronautical configurations. A Reynolds-averaged Navier-Stokes formulation is adopted and is solved using an unstructured implicit finite volume approach. The ONERA M6 wing is the configuration adopted for the present study. A total of 49 different grids is evaluated for this wing geometry under two flow conditions. The results obtained indicate that a variation of as much as 0.7 drag counts is expected on drag values due to the mesh effects alone, considering a 95% confidence level, in a total absolute drag of about 96 drag counts. The main contribution of the present Paper is to increase awareness of the need to assess dispersion when performing computational fluid dynamics computations and, in particular, in drag prediction. The Paper also contributes to quantifying the uncertainty associated with the use of unstructured computational meshes.