1316 
the line of contact T between the reflected plane shock R 
and the incident one is always on the wall. The phenomenon 
is evidently stationary for an observer moving with the line 
of contact (cf. fig. 7b) so that it is determined by the 
Fige 7 
WALL WALL 
kinematical condition that the relative flow of the fluid 
is parallel to the wall both initially and finally. Now the 
only changes in material velocity are normal to the shocks, 
viz., vat the incident shock of strength £ and Vat the 
reflected shock of strength ©. Since the total change of 
material velocity normal to the wall must be zero, for 
normalization in the region between the two shocks, 
vcos& + ucos a’=0 (9a 
Furthermore, the total change of material velocity parallel 
to the wall must be equal to the difference between the 
initial parallel velocity and the final one, i.e., 
e 
-u': Vee) eo) Pinay Dee 
usinga- VU sine = A, See (9b 
2 6g° 
