RotLES: A Rotorcraft-based Lattice Boltzmann LES code for Rapid Analysis and Design Space Exploration

In this NASA-TM, an overview is provided of an exploratory study into developing an LBM rotorcraft based LES tool called RotLES. Approaches explored in the RotLES code are designed to allow for rapid analysis and design space exploration all within the context of a user-friendly, minimal setup required framework. In RotLES, handling of solid body geometries and rotor modeling is designed to require minimal user setup, thus allowing for rapid case generation. Solid body geometries can be modeled automatically from a user provided STL file. Rotor modeling is handled through either actuator disk or actuator line source term modeling, both being defined using rotor definitions commonly available in both early stages conceptual and preliminary vehicle design. To enable rapid analysis with large scale grids, RotLES is coded using the NVIDIA CUDA language with CUDA aware OpenMPI. The inclusion of multi-GPU processing allows for scalable and rapid case turn around, allowing for multi-rotor unsteady simulations with billions of lattices to run in just a few hours. For validation of the RotLES model, outwash predictions for a single rotor are presented. Results showed RotLES closely tracks blade-resolved OVERFLOW predictions while greatly reducing overall computational expense. In closing remarks, a list of suggested future work is provided.