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More MHD

General Relativity (GR)

Started seriously on special relativity this week. Spent most of Monday on homework along with parts of Wednesday.

Magnetohydrodynamics (MHD)

Spent all of Tuesday and most of Wednesday on this. Reading through Teyssier and preparing for my presentation on MHD for the computational physics seminar people. Dug into some more details on Alfvén and magnetosonic waves (“magnetosonic” is easily the coolest word), these 4 extra waves significantly complicated the solution to the Riemann problem and so an exact solver isn’t really practical at all. The most popular solver is the HLLD solver (Miyoshi & Kusano 2005) which I will be implementing for my/Cholla’s MHD code.

mhd waves Note the much more complex wave structure now that the sound waves have split into the fast and slow magnetosonic waves

Computational Tools

I spent Thursday writing a C++ class for performance timing. It can be found in my hydro-sandbox in the file named PerfTimer.h. This new timer starts and stops with simple member functions, handles all the converting and cleaning of timing data, and outputs performance timing statistics in a neat and clean way. It can also directly save the timing data so more in depth analysis can be done.

I’ve started converting my hydro code in hydro-sandbox to use a Van Leer integrator instead of a CTU integrator so that I can use the VL+CT method for MHD detailed in Stone & Gardiner 2009.

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