40 



Figure 28 - Extension of Riabouchinsky 



Model to Two -Dimensional Wedges by 



Plesset and Shaffer— Reference ~[2 



An extension of the Riabouchinsky model to two-dimensional wedges, 

 Figure 28, has been carried out by Plesset and Shaffer. 72 As an approximation 

 to cones, they assumed that the pressure distribution is nearly the same as 



that found from the two-dimensional 

 flow about a wedge of the same in- 

 cluded angle. Their comparison of 

 the results obtained using this as- 

 sumption with Reichardt's data is 

 shown in Figure 29. As might have 

 been anticipated, the theoretical 

 drag coefficients are somewhat high, 

 but, nevertheless, the agreement is . 

 reasonably good for all cases except 

 the 14° included angle. The writers 

 offer no explanation for this large 

 discrepancy. However, it might be 

 pointed out that, for such small 

 entrance angles, boundary layer ef- 

 fects may become of importance and 

 separation may occur somewhat for- 

 ward of the downstream edge with a 

 resultant alteration in the boundary 

 conditions. It is also of interest 

 that the curves of Plesset and 

 Shaffer are fitted very well by 

 Equation [21 ] . 



The length of the two- 

 dimensional cavity formed behind a 

 plate and the breadth at the maximum 

 section have been given in various 

 forms by the writers cited. The re- 

 sults of the exact solution for the 

 Riabouchinsky model, stated in terms 

 of parameters k and a , in the form given by Gurevich are as follows: 

 The cavitation number is 



,_P -(1 + Vl - k 2 ) 



Figure 29 - Comparison of Theory of 



Plesset and Shaffer with Reichardt's 



Data for Discs and Cones — From 



Reference J2 



2V\ 



\-f 



The length of the cavity a is 



-M 1 - E - 



ulk 2 E 



