Cetin Kiris

Computational Fluid Dynamics (CFD) using Reynolds Averaged Navier Stokes (RANS) based closure modeling has become a cornerstone of aerodynamic analysis, driven by advancements in high-performance computing. While efficient algorithms for rapid steady-state modeling have matured RANS simulations over the past two decades, most efforts have focused on attached flow conditions, which represent less than 25% of the total aerodynamics development effort.

As CFD expands beyond design and optimization towards Certification and Qualification by Analysis, there's growing interest in high-fidelity numerical modeling for flight envelope regions characterized by large separated flows. These flows are significantly influenced by large-scale turbulence dynamics, and most RANS closures have limited success in such conditions. While this has led some manufacturers to incorporate scale-resolving simulations, widespread use of technologies like Wall Modeled Large Eddy Simulations (WMLES) remains limited due to the high computational cost and lack of automation in LES-quality grid generation for complex geometries.

This talk will demonstrate that automated Cartesian octree grid generation and an accurate high-Reynolds number viscous immersed boundary treatment for complex geometries can effectively address the grid generation bottleneck. Furthermore, carefully designed non-dissipative discretizations, implemented via a highly optimized software stack leveraging modern GPUs, can enable accurate LES at a computational cost comparable to RANS simulations using existing commercial software. The presentation will showcase detailed LES investigations of engineering problems involving separated flow aerodynamics and aeroacoustics. These simulations were performed on modest compute resources using 2 to 8 general-purpose GPU cards like the Nvidia RTX-4090 and Nvidia L40S. This breakthrough has the potential to enable LES utilization for a wide range of off-design flight characteristics without requiring access to DOE-class supercomputers.

Biography

After a distinguished 35-year journey at NASA, Dr. Cetin Kiris is now the CEO and founder of an early-stage technology startup that focuses on providing physics-based simulation capabilities to accelerate digital transformation of physical prototyping to predictive, fast, and cost-effective computing. Prior to his departure from NASA, Dr. Kiris served as the branch chief of the Computational Aerosciences Branch at NASA Ames Research Center. He initiated and orchestrated the development of LAVA, a computational framework for Launch, Ascent, and Vehicle Aerodynamics. He received his master's degree and Ph.D. in Aeronautics and Astronautics from Stanford University. He has published over 200 technical papers and co-authored a book on numerical simulations of incompressible flows. He has received numerous honors and awards, including NASA Outstanding Leadership Medal; NASA Exceptional Achievement Medal; NASA Software of the Year Award; NASA Commercial Invention of the Year Award for co-developing the NASA-DeBakey Ventricular Assist Device.