Philip Marcus
Professor Emeritus of Mechanical Engineering
Tien-Modak Chancellor’s Chair in Engineering
University of California Berkeley
Seminar Information
Engineering Building Unit 2 (EBU2)
Room 479
Seminar Recording Available: Please contact seminar coordinator, Jake Blair at (j1blair@ucsd.edu)
Although Jupiter’s Great Red Spot (GRS) has been of interest since Robert Hooke observed in 1664, there has been no 3D numerical simulation of it until this year. This is because the GRS occurs in a turbulent, rapidly-rotating atmosphere, with its top in a very stratified part of the atmosphere, and its bottom in a convection zone. A variety of physical processes (internal waves, inertial waves, local convection, strong shear, and strong rotation, along with numerous instabilities) control the GRS, and each process acts on a different time and space scale. All these processes must be accurately simulated, so this problem is numerically challenging. We approach the problem using an initial-value and carry out a search over initial-condition space to determine what, if any, conditions lead to a stable vortex that agrees with the velocity and temperatures observations obtained from the Hubble Space Telescope, the James Webb Space Telescope, and the Juno satellite. Our search required over 300 simulations with 500 X 500 X 500 spectral modes (equivalent to 6000 X 6000 X 6000 finite difference points), so the initial-value code needed to be fast. We found that the region of initial-value space that led to a stable vortex that agreed with all the observation is, for all practical purposes, unique. Our calculations give specific heights for the bottom, top, and middle of the Great Red Spot with little freedom for changes in these heights without the simulation becoming unstable or differing qualitatively from the temperature observations. An unusual property of the GRS is that it is “hollow” with no vorticity at its center. Our simulations reproduce this result. We know of no other hollow vortices either in the lab or in nature, but since simulating this hollow vortex, we believe that we know the physics that governs it, and we are currently collaborating with colleagues to design an experiment to build a hollow vortex in the lab.
Philip Marcus is the Tien-Modak Chancellor’s Chair in Engineering, emeritus at the University of California at Berkeley, and a Professor of Fluid Dynamics in the Department of Mechanical Engineering and in the Program in Applied Science & Technology. He is a former associate editor of The Journal of Computational Physics and of The Journal of Fluid Dynamics. He is a Fellow of the American Physical Society and a former Chair of its Division of Fluid Dynamics. He received his BS in Physics from Caltech and his PhD in Physics from Princeton. Before he came to UC Berkeley, he was a post-doc at Cornell and a professor in Applied Mathematics at MIT and professor of Astronomy and of Applied Mathematics at Harvard. He is interested in a wide range of fluid flows: from rotating, stratified turbulence, to the zombie vortex instability, to the formation of stars and planets, to ocean vortices, and to laboratory flows to the use of novel ways of carrying out three-dimensional morphing and using that framework along with Bayesian Optimization to “optimally design” aerodynamic hydrodynamic devices. He has developed a variety of algorithms for large-scale computational fluid dynamics that incorporate spectral methods.