HYDRODYNAMICAL RELATIONS U 



and for estimates of magnitude may be approximated by 



AC0(>S) ^ TavAS 



where Tav is the mean temperature. For a final pressure of 3.10^ 

 lb. /in. 2 we obtain 



Aco(,S) = 330-0.06-4.19 = 83 joules/gm. 



80 



70 



60 



50 



20 



10 



500 



o 



UJ 



200 



lor 



2 4 6 8 10 12 



PRESSURE (kILOBARS) 



14 



Fig. 2.4 Velocities at a shock front as a function of pressure for low pressures. 



which is less than 5 per cent of the change of 1,750 joules/gm. at con- 

 stant entropy. 



An interesting consequence of the result is that the F-Y curve for 

 the shock wave passes, at about 360,000 Ib./in.^ pressure, through a 

 region found by Bridgman to be a solid state of equilibrium which he 

 labelled "Ice VII." This order of pressure is realized at a distance of 

 about two charge radii for TNT, but the actual formation of ice by the 

 shock wave is not to be expected in the times that the water remains in 



