Summary of Data from the Sixth AIAA CFD Drag Prediction Workshop: Case 1 Code Verification.

Area of Science:

• Computational Fluid Dynamics (CFD)
• Aerodynamics
• Turbulence Modeling

Background:

• The Sixth AIAA CFD Drag Prediction Workshop (DPW-VI) Case 1 focused on code verification for turbulent flow over a 2D NACA 0012 airfoil.
• Reynolds-Averaged Navier-Stokes (RANS) turbulence models were employed, with a benchmark solution available for the Spalart-Allmaras (SA) model.

Purpose of the Study:

• To assess the accuracy and consistency of computational fluid dynamics (CFD) codes used for aerodynamic analysis.
• To verify that numerical algorithms and software implementations are free from programming errors.

Main Methods:

• 31 submissions from 16 teams were analyzed, primarily using various versions of the Spalart-Allmaras (SA) model.
• Other turbulence models included k-omega SST, k-kl, k-epsilon, an algebraic Reynolds stress model, and Lattice Boltzmann Method (LBM) with Very Large Eddy Simulation (VLES).
• Diverse grid types such as structured, unstructured, Cartesian, and adapted grids were utilized.

Main Results:

• 21 submissions using standard SA model variants were considered for the benchmark.
• While many submissions demonstrated first-order convergence, several exhibited nonconvergent solutions or incorrect results for aerodynamic forces and moments.
• Discrepancies were observed even with standard SA model implementations, including SA-noft2 and SA-neg variants.

Conclusions:

• Rigorous code verification is crucial and must be performed before design, model validation, and analysis studies.
• The study underscores the challenges in achieving reliable CFD solutions and the importance of verifying numerical methods.
• Inconsistent results highlight the need for standardized verification procedures in aerodynamic research.