ABSTRACT 



Resistance has been measured of nine bodies of revolution, having equal 

 volume but varying forebody shapes. Forebody shapes ranged from extremely 

 blunt to extremely fine and included two that were flat faced. The forebodies 

 were altered by changing their length-to-diameter ratios (L/D's) and prismatic 

 coefficients. Drag results indicate that when the prismatic coefficient is fixed 

 and the L/D is decreased, the residual resistance will increase modestly. 

 Increasing the prismatic coefficient at small L/D's increases residual resistance; 

 however, at moderate L/D's it does not. The results suggest that a flat-faced 

 shape in itself does not increase resistance. 



In addition to resistance experiments, transition regions on the models 

 were located, using hot film probes. Calculations predicted laminar separation 

 on five of the model forebodies. The hot film measurements confirmed that 

 separation did occur at the locations predicted; downstream of the separation 

 locations, turbulent flow occurred immediately. The remaining four fore- 

 bodies exhibited well-defined natural transition regions. Flow properties in 

 the transition regions, measured by the hot film gages have been compared 

 with predicted spatial amplification ratios of disturbances, calculated by 

 linear stability theory. Results have failed to show a single relationship 

 between measured flow properties and computed spatial amplification ratios. 

 Correlation of amplification factors with flow regimes varied, both with 

 forebody shape and Reynolds number. 



ADMINISTRATIVE INFORMATION 



This work was funded and authorized by the Naval Sea Systems Command under the 

 hydrodynamics part of the very high speed submarines program, Task Area SF 434 215 1Z, 

 Work Unit 1-1520-004, and the improvements in submarine hydrodynamics program, Task 

 Area SSL66007, Work Unit 1-1552-135. 



INTRODUCTION 



Experiments have been conducted on nine bodies of revolution having different forebody 

 shapes. The primary purpose of the experiments was to determine what effect changing 

 forebody shape would have on resistance. As a means to this end, the roles of transition, 

 laminar separation, and turbulence stimulation in the analysis of model data have also been 

 investigated. These phenomena have been examined using hot film probes, located in the 

 model surfaces - resulting in a new method for analyzing model drag data as reported by 

 McCarthy, Power, and Huang. 1 Results of both the resistance and hot film measurements are 

 presented in this report. 



1 



