MAESTRO: Low Mach Number Astrophysics
Overview
As part of the SciDAC Computational Astrophysics Consortium we have developed a new low Mach number hydrodynamics code, MAESTRO, that includes stellar equations of state and nuclear reaction networks. We are currently using MAESTRO to study the convective phase of Type Ia supernovae and Type I Xray bursts.
Development of MAESTRO is in collaboration with Mike Zingale at Stony Brook Univeristy.
MAESTRO Download
To get a copy of the latest version of the MAESTRO repository using git, please visit our Downloads page.MAESTRO Email Support List
If you are interested in using MAESTRO, please join our MAESTRO mailing list to receive any updates and see questions other users are asking: https://groups.google.com/forum/#!forum/maestrohelp .

White Dwarf ConvectionFor a great overview of our white dwarf convection and ignition studies using MAESTRO, see Mike Zingale's White Dwarf Convection page. 
Why A Low Mach Number Approach?
A large number of interesting astrophysical phenomena occur in the low Mach number regime, where the characteristic fluid velocity is small compared to the speed of sound. Evolving these flows with a fully compressible simulation code is inefficient because
these codes compute the effect of sound waves, which are unimportant for our problems of interest.
For an explicit timediscretization (i.e., the new state is expressed solely in terms of the present state), a fundamental limitation exists
on the size of the allowable timesteps  the CFL condition. A timestep is restricted such that information may only propagate across one zone in the computational grid per timestep. In compressible flow, information propagates at the speeds: u,
Our desire is to reformulate the equations of hydrodynamics to filter out sound waves, while retaining the compressibility effects important to the problem at hand. This will result in a timestep constraint of the form
MAESTRO Features
Coordinate Systems
MAESTRO supports calculations in 2D and 3D Cartesian coordinates.Unsplit PPM Hydrodynamics
MAESTRO uses an unsplit version of the piecewise parabolic method (PPM), with new limiters that avoid reducing the accuracy of the scheme at smooth extrema.Modular Equation of State and Reaction Networks
MAESTRO is written in a modular fashion so that the routines for the equation of state and reaction network can be supplied by the user. The reactions are included in the time integration scheme in a secondorder accurate operatorsplit formulation (Strang splitting).AMR in MAESTRO
Our approach to adaptive refinement in MAESTRO uses a nested hierarchy of logicallyrectangular grids with refinement of the grids only in space, i.e. all levels are advanced with the same time step. The integration algorithm on the grid hierarchy is such that each substep of a time step is completed at all levels before proceding to the next substep. Data is synchronized between levels at the completion of each substep.During the regridding step, increasingly finer grids are recursively embedded in coarse grids until the solution is sufficiently resolved. An error estimation procedure based on userspecified criteria evaluates where additional refinement is needed and grid generation procedures dynamically create or remove rectangular fine grid patches as resolution requirements change.
Visualization
Software Framework
The MAESTRO software is written in the Fortran90 BoxLib software framework developed by CCSE.Questions?
Contact Ann Almgren.

MAESTRO in the News: First Full Simulation of Star's Final Hours. 
MAESTROrelated Publications
M. Zingale, C. M. Malone, A. Nonaka, A. S. Almgren, and J. B. Bell, "Comparisons of Two and ThreeDimensional Convection in Type I Xray Bursts," submitted for publication [pdf].
A.M. Jacobs, M. Zingale, A. Nonaka, A.S. Almgren, J.B. Bell, "Low Mach Number Modeling of Convection in Helium Shells on SubChandrasekhar White Dwarfs II: Bulk Properties of Simple Models," submitted for publication, 2015 [arxiv].
M. Zingale, A. Nonaka, A. S. Almgren, J. B. Bell, C. Malone, and R. Orvedahl, "Low Mach Number Modeling of Convection in Helium Shells on SubChandrasekhar White Dwarfs. I. Methodology", Astrophysical Journal, 764, 97, 2013.
Ann Almgren, John Bell, Andy Nonaka and Michael Zingale, "Low Mach Number Modeling of Stratified Flows," Finite Volumes for Complex Applications VII  Methods and Theoretical Apsects, Springer Proceedings in Mathematics and Statistics, eds. J. Fuhrmann, M. Ohlberger, C. Rohde, Berlin, June 2014. [link]
C. M. Malone, M. Zingale, A. Nonaka, A. S. Almgren, and J. B. Bell, "Multidimensional Modeling of Type I Xray Bursts. II. TwoDimensional Convection in a Mixed H/He Accretor", Astrophysical Journal, 788, 115, 2014. [arxiv]
C. Gilet, A.S. Almgren, J.B. Bell, A. Nonaka, S.E. Woosley and M. Zingale, "LowMach Number Modeling of Core Convection in Massive Stars", Astrophysical Journal, 773, 137, 2013. [pdf]
A. Nonaka, A. J. Aspden, M. Zingale, A. S. Almgren, J. B. Bell, and S. E. Woosley, "HighResolution Simulations of Convection Preceding Ignition in Type Ia Supernovae Using Adaptive Mesh Refinement", Astrophysical Journal, 745, 73, 2012. [pdf]
M. Zingale, A. Nonaka, A. S. Almgren, J. B. Bell, C. M. Malone, and S. E. Woosley, "The Convective Phase Preceding Type Ia Supernovae", Astrophysical Journal, 740, 8, 2011. [pdf]
A. Nonaka, A. S. Almgren, J. B. Bell, H. Ma, S. E. Woosley, and M. Zingale, "From Convection to Explosion: EndtoEnd Simulation of Type Ia Supernovae," Proceedings of SciDAC 2011, Denver, CO, July 2011. [pdf]
C. M. Malone, A. Nonaka, A. S. Almgren, J. B. Bell, and M. Zingale "Multidimensional Modeling of Type I Xray Bursts. I. TwoDimensional Convection Prior to the Outburst of a pure ^{4}He Accretor", Astrophysical Journal, 728, 118, Feb. 2011. [arxiv]
A. Almgren, J. Bell, D. Kasen, M. Lijewski, A. Nonaka, P. Nugent, C. Rendleman, R. Thomas, M. Zingale, "MAESTRO, CASTRO and SEDONA  Petascale Codes for Astrophysical Applications," SciDAC 2010, J. of Physics: Conference Series, Chattanooga, Tennessee, July 2010. [arxiv]
H. Ma, M. Zingale, S. E. Woosley, A. J. Aspden, J. B. Bell, A. S. Almgren, A. Nonaka, and S. Dong, "Type Ia Supernovae: Advances in Large Scale Simulation," Proceedings of SciDAC 2010, Chattanooga, TN, July 2010. [pdf]
A. Nonaka, A. S. Almgren, J. B. Bell, M. J. Lijewski, C. M. Malone, and M. Zingale, "MAESTRO: An Adaptive Low Mach Number Hydrodynamics Algorithm for Stellar Flows", Astrophysical Journal Supplement Series, 188, 358383, June 2010. [pdf] [arxiv]
M. Zingale, A. S. Almgren, J. B. Bell, A. Nonaka, and S. E. Woosley, "Low Mach Number Modeling of Type Ia Supernovae. IV. White Dwarf Convection", Astrophysical Journal, 704, 196210, 2009. [pdf]
S. E. Woosley, A. S. Almgren, A. J. Aspden, J. B. Bell, D. Kasen, A. R. Kerstein, H. Ma, A. Nonaka, and M. Zingale, "Type Ia Supernovae: Advances in Large Scale Simulation ", SciDAC 2009, J. of Physics: Conference Series, 180, July 2009. [pdf]
A. S. Almgren, J. B. Bell, A. Nonaka, M. Zingale, "A New Low Mach Number Approach in Astrophysics", Computers in Science and Engineering, vol. 11, no. 2, pp. 2433, March/April 2009. [CiSE]
M. Zingale, A. S. Almgren, J. B. Bell, C. M. Malone and A. Nonaka, "Astrophysical Applications of the MAESTRO Code", SciDAC 2008, J. of Physics: Conference Series, 125, Seattle Washington, July 2008. [pdf]
A. S. Almgren, J. B. Bell, and M. Zingale, "MAESTRO: A Low Mach Number Stellar Hydrodynamics Code ", SciDAC 2007, J. of Physics: Conference Series, Boston, Massachusetts, July 2007.
A. S. Almgren, J. B. Bell, A. Nonaka, and M. Zingale, "Low Mach Number Modeling of Type Ia Supernovae. III. Reactions", Astrophysical Journal, 684, 449470, 2008. LBNL Report LBNL58673 Pt. III. [pdf]
A. S. Almgren, J. B. Bell, C. A. Rendleman, and M. Zingale, "Low Mach Number Modeling of Type Ia Supernovae. II. Energy Evolution", Astrophysical Journal, 649, 927938, 2006. LBNL Report LBNL58673 Pt. II. [pdf]
A. S. Almgren, J. B. Bell, C. A. Rendleman, and M. Zingale, "Low Mach Number Modeling of Type Ia Supernovae. I. Hydrodynamics", Astrophysical Journal, 637, 922936, 2006. LBNL Report LBNL58673. [pdf](revised)