[atmcfd]

i`m going through anderson`s 'CFD and its applications",and i`m stuck on pg. 308
(analysis of quasi one dimensional subsonic-supersonic nozzle). here the initial condition of density,temperature and velocity is given by the equations

p = 1 - 0.3146x
T = 1 - 0.2314x . initial conditions at t = 0
V = (0.1 + 1.09x)T^1/2
where 'x' is the axis where the grid points are evenly spaced

forgive me if dis question`s stupid, but what is the origin of these eqns? there is no explanation offered in the text as to what are the governing principles behind these. are these just taken arbitrarily or what...
please help.

thanks in advance,
atm