39 



The results of drag measurements made by Reichardt 54 and the TMB 

 drag measurements 40 on various axisymmetric obstacles are shown in Figure 2~[ . 











DRA 



i i i i i 



G OF CAVITATING HEAD 



Ff 



)rm: 



NOT 



1 — 



















o DISC 















I: CURVES EXTENDED TO 0"=0 ARE OF THE FORM 















& HEMISPHERE 















c„(a-) = c D (0)(i*o-) 

























14 



> H REICHARDT CONICAL BODIES 

 o H. REICHARDT CIRCULAR DISC 















































° H REICHARDT SC 



uUF 



RIN 















































1.2 



. — - S^ 



















































=- 









il 





a 





























^ 





rr=-- 



-==- 



^'' 

















__- 



ase 



u!t 





























"' 











""" /"""' 







1.0 



r 



f" 























1 





I 



— - 



— - 



--" 





































0.8 





































































r^'hztr- 











































06 













-% h—i- 







































































































04 



r% 



„,Ji 





































-(TMB) 















i_ t .H— r*~ 















































02 





— 































































































2-1 SEMIELLISOID (TMB) 





















































1 









0.3 



04 



05 



CAVITATION INDEX 0" 



Figure 27 - Drag of Various Models at Different Cavitation Numbers 



In this figure, the curves which are extrapolated down to a = are of the 

 form of Equation [21]. The correlation of the TMB data and Reichardt's data 

 with Equation [21 ] is very good over a rather wide range of cavitation numbers. 

 It will further be seen that Reichardt's data for cones appear to be on a line 

 defined by Equation [21 ]. However, the slope of drag curves for the forms 

 with surface curvature is somewhat greater. This difference might be attrib- 

 uted to the fact that for the disc and cones the point of separation is fixed 

 at the downstream edges for all cavitation numbers; for the curved surfaces, 

 on the other hand, the separation point was observed in the TMB tests to shift 

 with changing cavitation number. A part of this shift may be attributed to 

 the dependence of the pressure distribution and boundary-layer growth on 

 Reynolds number, 71 but the largest part is probably associated with the curva- 

 ture of the surface. The extension of free-streamline theory with finite cav- 

 itation numbers for curved surfaces will be required to throw more light on 

 this point. (The two-dimensional cavity for a = behind curved forms has 

 been treated by Levi-Civita, see- Reference 6o. ) 



