HYDRODYNAMICAL RELATIONS 



61 



than a, the increase being greater for stronger shock fronts. The maxi- 

 mum vahie of a for regular reflection decreases with increasing P/Po, 

 the Umiting value being indicated by the line marked extreme. A 

 corresponding set of curves for the reflected pressures is plotted in Fig. 



UJ 



-I 

 o 

 z 

 < 



90° I ^-^— -4 



75' 



Z 



2 60 



E ^s** 



30 



15" 



Of 15* SO'* 45° 60° 



ANGLE OF INCIDENCE OC 



75' 



90' 



Fig. 2.11 Angle of reflection a.' as a function of angle of incidence a. for 

 shock fronts of different strengths. 



2.12. Rather than plotting P' jPo it is found convenient to use the 

 auxiliary variable ^ defined by 



r = 



P' ^B 

 Po + B 



It is seen from the plot that the strength of the reflected wave, as 

 measured by ^', increases significantly for sufficiently large values of a 

 and P/Po. For example, for P = 37,500 Ib./in.^ {P/P, = W) and 

 an angle of incidence of 40°, the pressure P' behind the reflected wave 



