[FLASH-USERS] Relativistic hydrodynamics

[Geoff Bicknell]

Dear Flash community:

I am looking at the relativistic solver in FLASH and I may enhance 
that to be give better spatial accuracy. However, for the present, I 
am a bit confused by the units.

In general I am used to setting up simulations so that quantities are 
of order unity and then I  scale variables according to the the 
allowable scalings that are present in the problem (e.g. see 
Sutherland & Bicknell 2007, ApJ for an example of this approach). 
FLASH does things differently by insisting that one adopts specific 
physical scales. Given the wide range of problems for which FLASH is 
envisaged, this is fair enough; one can still scale the results.

However, I am a bit mystified by the write-up on the RHD solver in 
the FLASH manual. There the equations are written with a velocity 
scale such that c=1. However, the velocity scale in the physical 
constants unit is not arbitrary. Does one define the length and time 
units so that c=1?

Regards,
Geoff Bicknell

-- 
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Professor Geoffrey Bicknell
Research School of Astronomy & Astrophysics, Australian National University,
Mt Stromlo Observatory, Cotter Rd., Weston ACT 2611, AUSTRALIA
T:+61 (0)2 6125 0245 M: +61 (0)402 302 802  F: +61 (0)2 6125 0233
W: http://www.mso.anu.edu.au/~geoff
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