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DTSTART;TZID=America/Chicago:20181111T140600
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UID:submissions.supercomputing.org_SC18_sess160_ws_whpc128@linklings.com
SUMMARY:Efficient Application of Low Mach Number Hydrodynamics Code to Ste
 llar Flows
DESCRIPTION:Duoming Fan (Lawrence Berkeley National Laboratory)\n\nAstroph
 ysical phenomena that occur in the low Mach number regime are often comput
 ationally expensive because the time step is constrained by both the chara
 cteristic fluid velocity and, by comparison, the much larger speed of soun
 d. In addition, astrophysical flows are generally highly turbulent, and co
 nsiderable computational cost is required to resolve the local flow in sma
 ller regions of interest. We introduce MAESTROeX, a low Mach number hydrod
 ynamics code for computing stellar flows that uses the AMReX C++/F90 libra
 ries and software structure. By filtering out the acoustic waves from the 
 governing equations, MAESTROeX uses a time step constraint that is based o
 nly on the fluid velocity rather than the sound speed. It also incorporate
 s adaptive mesh refinement (AMR) to efficiently increase spatial resolutio
 ns by locally refining the grid in the regions of interest. Additionally, 
 to allow the proper capture of the effects of an expanding star, MAESTROeX
  uses a novel one-dimensional radial base state whose evolution is coupled
  to the evolution of the full state. In our latest attempt to improve the 
 local hydrodynamic equilibrium errors caused by the radial base states, th
 e base states are now computed at uneven intervals as to directly map to t
 he Cartesian grid. The performance and scalability of MAESTROeX are evalua
 ted on NERSC and OLCF systems scalable to over 100K cores. Future work inc
 ludes improving the current algorithm and offloading simple subroutines to
  GPUs to increase computational efficiency, and incorporating new physics 
 into the system such as those needed for rotating stars.\n\nTag: Diversity
 , Education, Hot Topics\n\nRegistration Category: Workshop Reg Pass\n\nSes
 sion Chairs: Toni Collis (Women in High Performance Computing); Weronika F
 ilinger (Edinburgh Parallel Computing Centre (EPCC); University of Edinbur
 gh, Scotland); and Misbah Mubarak (Amazon Web Services)\n\n
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