Simulation-Enabled Discoveries in Fluid Turbulence
TimeWednesday, June 19th2:45pm - 3:15pm
DescriptionComputation has emerged as the indispensable third leg of scientific discovery along with the traditional two branches of theory and experiment. In this talk we discuss discoveries that resulted from high-performance simulations of turbulent and magnetohydrodynamics (MHD) flows.
We present results from DNS (direct numerical simulation) and LES (large-eddy simulation) of convective turbulence and wall-bounded turbulent flows. An open question in convective turbulence pertained to the scaling behavior of the energy spectrum. Our largest spectral simulation at a resolution of 40963 led to the conclusion that the energy spectrum follows the Kolmogorov scaling (k-5/3).
An open question in wall-bounded turbulent flows is whether the mean velocity profile obeys a log-law or a power-law. Our LES results at extremely large Reynolds numbers (Re~1011) provide strong evidence that turbulence gravitates naturally towards the log-law scaling. Another interesting discovery is about the so-called “drag crisis”, i.e., the drag undergoes a drastic reduction at Re~300,000. Our LES have overturned the conventional wisdom that the drag crisis is due to the transition of the boundary layer from a laminar to a turbulent state.
We believe these case studies amply demonstrate that simulation enabled discoveries are no longer a myth, and that computations are a legitimate tool to answer clearly posed questions in science and engineering.
Acknowledgement: The Cray XC40 Shaheen II at KAUST was used for all simulations reported. This research was partially supported under the KAUST Competitive Research Grant funds and baseline research funds of R. Samtaney.