The NextSim project aims at significantly improving the performance of computer simulations of flows around air vehicles and making this capability available to the European aeronautics industry. At the beginning of the project a suite of industrially relevant test cases and scenarios were defined, along with reference results obtained with the next generation Computational Fluid Dynamics (CFD) software CODA in its initial status.
After one year, some of the simulation scenarios have been revisited and computed with an updated version of the software in order to assess the progress made through the development activities along the project. A direct one-to-one comparison of the achieved runtime on the same HPC cluster allows to quantify and assess the impact on specific simulation scenarios. As an example, the figures below demonstrate a third-order Discontinuous Galerkin simulation of the NASA Common Research Model configuration under high-lift conditions on a relatively coarse computational mesh. As previously confirmed, the results obtained in terms of aerodynamic lift and drag coefficients compare favorably with results in previous international workshops.
The runtime to achieve a fully converged solution could be reduced to less than half as compared to the initial status on the same number of processors by exploiting new and improved solver settings w.r.t. the implicit solution algorithm. With the perspective of the future adoption of these improvements in an industrial environment it is important to establish best practice guidelines for the required solver parameters. The NextSim project will explicitly address this challenge in the last year of its duration. In view of this perspective it is particularly interesting that the settings exploited in the example shown here have not been obtained via optimization on the given scenario itself, but have been transferred from experience obtained on a different scenario of an aircraft under cruise flight conditions, solved with a Finite Volume numerical scheme (in CODA). Thus, the successful transfer to this new case already demonstrates first steps towards defining a best practice approach.
Computer simulation of the air pressure on the surface of a simplified aircraft model in high-lift conditions during landing. A higher-order numerical method (Discontinuous Galerkin) has been used to produce the results. Credit: DLR (CC BY-NC-ND 3.0)
Residual convergence of the simulation, indicating that the runtime could be reduced by over 50% with improved algorithms and solver settings. Credit: DLR (CC BY-NC-ND 3.0)