Joseph Barranco - Computational Fluid Dynamics Lab

Computational Fluid Dynamics Laboratory

Joseph Barranco
barranco@kitp.ucsb.edu

NSF Astronomy & Astrophysics Postdoctoral Fellow

Kavli Institute for Theoretical Physics
Kohn Hall, University of California
Santa Barbara, CA 93106
(805) 893-4092

Joseph is investigating the dynamics of 3D vortices in protoplanetary disks (thin, cool disks of gas and dust in orbit around newly forming protostars) with a parallel spectral code on the Blue Horizon supercomputer. Some of the lingering questions he addresses are: What is the structure of 3D vortices in a protoplanetary disk? Are they columns that extend vertically through the disk, through many scale heights of pressure and density? Or are they more "pancake-like" and confined to the mid-plane? Are the vortices stable to small perturbations, such as vertical shear? Are 3D vortices robust and long-lived coherent structures? Do small vortices merge to form larger vortices the way vortices on Jupiter do?

One of the enduring puzzles in the formation of planetary systems is how millimeter-sized dust grains agglomerate to become kilometer-sized, self gravitating planetesimals, the "building blocks" of planets. One theory is that the dust grains settle into the mid-plane of the protoplanetary disk until they reach a critical density that triggers a gravitational instability to clumping. However, turbulence within the disk is likely to stir up the dust grains and prevent them from reaching this critical density. A competing theory is that dust grains grow by pair-wise collisions, forming fractal structures. It is unclear, however, how robust such structures would be to successive collisions. A new and exciting theory is that vortices in a protoplanetary disk may capture dust grains at their centers, "seeding" the formation of planetesimals.

Research Interests

Astrophysical and Geophysical Fluid Dynamics, Accretion Disks, Star and Planet Formation, Vortex Dynamics

Selected Publications

Barranco, J.A., Marcus, P.S., & Umurhan, O.M. 2000, "Scalings and Asymptotics of Coherent Vortices in Protoplanetary Disks," in Studying Turbulence Using Numerical Simulation Databases - VIII, Proceedings of the 2000 Summer Program, Stanford University/NASA-Ames Center for Turbulence Research, 85-95. Article

Barranco, J.A., & Marcus, P.S. 2000, "Vortices in Protoplanetary Disks and the Formation of Planetesimals," in Studying Turbulence Using Numerical Simulation Databases - VIII, Proceedings of the 2000 Summer Program, Stanford University/NASA-Ames Center for Turbulence Research, 97-108. Article

Barranco, J.A., & Goodman, A.A. 1998, "Coherent Dense Cores. I. NH3 Observations," The Astrophysical Journal. 504 207-222.

Goodman, A.A., Barranco, J.A., Wilner, D.J. & Heyer, M.H. 1998, "Coherence in Dense Cores. II. The Transition to Coherence," The Astrophysical Journal. 504 223-246.