Simulation Enabled Discoveries: Case Studies in MHD and Fluid Dynamics
16:00 - 16:30
Computation has emerged as the indispensible third leg of scientific discovery along with the traditional two branches of theory and experiment. In this talk we discuss some case studies from magnetohydrodynamics (MHD) and fluid dynamics based on research conducted in the Fluid & Plasma Simulation Laboratory.
Our first case study is that of magnetic suppression of the Richtmyer-Meshkov instability (RMI). In hydrodynamics, a density interface separating two fluids is unstable under impulsive acceleration. This instability aka RMI has been the bane of inertial confinement fusion where it is considered highly detrimental. The suppression of this instability in the presence of a magnetic field was a purely serendipitous discovery due to large-scale simulations.
The second case study is that of magnetic reconnection (MR). Loosely defined, MR is the breaking and reattachment of magnetic field lines, and is a somewhat ubiquitous phenomenon in our universe: it accompanies coronal mass ejections from our Sun, observed in the earth’s magneto-tail, etc. Standard quasi-steady models in single-fluid resistive MHD severely under predict the reconnection rate compared with observations. A key-missing piece of physics is an instability dubbed the plasmoid instability. Large-scale MHD simulations led to the discovery of this instability demonstrating that the reconnection rate saturates for Lundquist number greater than 104.
The fluid dynamics examples pertain to simulations of wall-bounded turbulence. Here we focus on the simulation of the drag crisis in flow over bluff bodies and show how large-eddy simulations can successfully reproduce this phenomenon.
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