Figure 14. Photograph of flow past yawed wedge. 



the pressure distribution on the upper face OA is the same as if this face were half 

 a wedge AOA' of semi-angle /3 — 8, symmetrically placed in the stream (Fig. 17). 

 Similarly the pressure distribution on the face OB is assumed the same as on a wedge 

 BOB', of semi-angle /? + 8. If we expand these two distributions by Taylor's theorem 

 we then have, by resolving or taking moments, integrating and then letting tend to 

 zero, expressions for the lift-slope and moment-slope coefficients which are readily cal- 

 culated by numerical differentiation from the known pressure distributions. Experi- 

 ments have shown that this approach to the problem, when applied to the cone, at 

 least, gives good agreement with experiment for large cone angles (Fig. 18). This 

 result is in line with the corresponding results obtained by Plesset and Schaffer described 

 above. 



An alternative theory, which might be expected to yield good results for small 

 to moderate cone angles, is based on a modification of the well-known Munk-Jones 

 theory for slender bodies. For very slender bodies this theory assumes that the cross- 

 force may be obtained by considering the rate of change of momentum in the two- 

 dimensional flow on a plane perpendicular to the flow direction, and moving with the 

 free-stream velocity V. This yields the value 2/rad. for C L /a. Fig. 18 shows that as 

 yS — > 0, C L / a ~" > 2 experimentally. 



Since for the cavitating flow past moderately slender cones, the surface velocity 



V s 2 

 V s is constant over much of the surface (V s is given by — - =1 — C Do ) the condi- 

 tion that the flow must be tangential to the surface of the cone may, over most of 

 the surface, be met by letting the cross flow plane move with a velocity V s cos /? 

 past the body. 



229 



