Additives Injected Into the Boundary Layer of an Underwater Body 



15 

 Drag 

 Reduction -gms 



10 



O.ZSmm. Nose Slot 

 Flow Rote 1 3 ml/sec. 



500 ppm 



2,500 ppm 



100 200 300 400 500 600 700 



Tunnel velocity - cnn/sec. 



Fig. 13 - Drag reduction using POLYOX WSR-301 



being injected and to monitor the dye concentration in the wake of the body. A 

 series of runs was carried out at 450 cm/sec, using pure water and a 100 ppm 

 solution of POLYOX WSR-301. The dye used was Rhodamine 'B', which is de- 

 tectable to about 1 part in 10^^ by a fluorometer (Model 111, G. K. Turner, Palo 

 Alto, Calif.). The initial concentration of the dye in the fluids was 1 part in 10"*. 

 The flow rate through the slot was 30 ml/sec. 



Visual observations of the flow over the body indicated that the dye was al- 

 most immediately mixed into the boundary layer. The boundary layer thickness 

 at the downstream end of the cylindrical section of the body was about 0.3 cm. 

 Separation occurred over the tail section of the body, and the boundary layer at 

 the trailing edge appeared to be about 2.5 cm thick. The dye measurements 

 were made 7 cm downstream from the tail of the body. At this location the 

 boundary layer appeared to have about the same diameter as the cylindrical por- 

 tion of the body. 



The total head pressure in the working section of the tunnel, which is about 

 0.7 kilograms per square inch above atmospheric pressure, was used to draw 

 the fluid from the wake through a conical pilot probe, with a 2 mm opening, to 

 the fluorometer. The probe was mounted on a holder which could be continu- 

 ously moved across the wake and could be placed vertically in accurately meas- 

 ured steps. When the dye was injected the probe was moved at a known speed 

 through the wake and the output was recorded on a paper chart. The probe was 

 then moved vertically and the process repeated. The dye did not affect the 

 properties of the polymer solution, because the drag reduction was the same as 

 obtained for previous runs. 



987 



