42 HYDRODYNAMICAL RELATIONS 



this condition, as transitions of this kind take place very slowly. The 

 water is rather in a metastable condition not amenable to conventional 

 measurement. 



In use of the shock front data of Table 2.1, it is to be remembered 

 that the equation of state used is only approximate and involves con- 

 siderable extrapolation for pressures above 360,000 Ib./in.^ (25 kilobars) 



(a). Pressures up to 1.5 kilobars, initial temperature 15° C, acoustic sound velocity Co = 1500.5 

 m./sec. 



(b). Pressures up to 14 kilobars, initial temperature 25° C, acoustic sound velocity c<, = 152S.5 

 m./sec. 

 Data employed: 



y (T) : Knudsen's Tables, as given in Oceanographical Tables, compiled by Zubov, Commissariat 

 of Agriculture USSR, Moscow. 

 Co.- Values given by Mathews in Report HD-282, British Admiralty Hydrographic Office, 

 which also gives compressibility data of Ekman for pressures up to 1.5 kilobars. For 

 pressures up to 11 kilobars, the Tait equation was fitted to data of Adams, J ACS 63, 

 3769 (1931). 



Table 2.2 Properties of weak shock fronts in salt water (3.79 weight per cent NaCl) 

 from calculations of Arons and Halverson (4) . 



for want of experimental data. The values at higher pressures are 

 therefore of necessity increasingly uncertain, and the values at pressures 

 below 15 kilobars should be obtained from Table 2.2 and Fig. 2.4, which 

 are based on more accurate data on water at lower pressures. For ex- 

 ample, the velocity of sound at atmospheric pressure and 20° C. given 

 by Kirkwood is 4,797 ft. /sec, and the best value is about 4,967 ft./sec. 

 Penney (83) has also made calculations of shock front velocity, sound 

 velocity and particle velocity as a function of pressure behind the shock 



