Basic hydrodynamics and Introduction to FLASH Kuo-Chuan Pan ( ) - PowerPoint PPT Presentation

Basic hydrodynamics and Introduction to FLASH Kuo-Chuan Pan ( 潘國全 ) Institute of Astronomy, NTHU � 1 Numerical Astrophysics Summer School: Computational Astrophysical Fluid Dynamics, 2019.09.04, IoA, NTHU

Outline: •Astrophysical fluids •Basic hydrodynamic equations •Introduction to the FLASH code � 2 NA School: Comp. Astrophysical Fluid Dynamics, Sep 4-6, 2019, IoA, NTHU

Why we need simulations in Astronomy? •We receive and record, but we do not experiment or perturb (too distant) •Astrophysical systems involve extreme conditions that cannot be replicated in lab (mostly) •Timescales are >> human lifetime (mostly) � 3 NA School: Comp. Astrophysical Fluid Dynamics, Sep 4-6, 2019, IoA, NTHU

Observation and Computation Analogies Observation Data reduction / Calibration DATA Astrophysical object Telescope Detectors Simulation cool PN Supercomputer DATA Mathematical Model Codes Data analysis / Visualization � 4 NA School: Comp. Astrophysical Fluid Dynamics, Sep 4-6, 2019, IoA, NTHU

Frontier Astronomy Research Observations Theoretical Astrophysics Observational Astronomy Hypothesis Validation Realization Postdiction, Prediction Formulation Computational Astrophysics Michael Norman (1997) � 5 NA School: Comp. Astrophysical Fluid Dynamics, Sep 4-6, 2019, IoA, NTHU

Astrophysical Problems Stars/Binaries Planetary disk Interstellar medium (~0.1-1000 AU) (~100-1000 AU) (~10-100 pc) Planets (~ Earth radius) Large scale Galaxy Galaxy clusters � 6 structure (~50 kpc) (~1 Mpc) (~1 Gpc) � 6 NA School: Comp. Astrophysical Fluid Dynamics, Sep 4-6, 2019, IoA, NTHU

Astrophysical Simulations 2018 ApJ 2012 ApJ, 750, 151 2013MNRAS � 7 2012 ApJ, 746, 74 2009 MNRAS 398, 1082 2005 ApJS 160, 28 � 7 NA School: Comp. Astrophysical Fluid Dynamics, Sep 4-6, 2019, IoA, NTHU

Fluid Approximation •To solve the gas dynamics equations, one could use N-body method if we know the force between two particles. •However, the number of particles is usually huge (N A =10 23 ). It is impossible to use direct N-body method to study the gas dynamics. -> Fluid � 8 � 8 NA School: Comp. Astrophysical Fluid Dynamics, Sep 4-6, 2019, IoA, NTHU

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