The hole exited on the suction side at the location of the observed tip vortex 

 attachment point — at the foil midchord and approximately 0.10 in. (0.00254 m) in- 

 board of the tip. Two channel diameters were investigated, 0.125 in. (0.0032 m) and 

 0.188 in. (0.0048 m) , and they were drilled at an angle of 10 deg with respect to the 

 foil chordline. Figure 9 shows an overall view and a tip closeup of the 0.125 in. 

 (0.0032 m) channel model. 



For the active mass injection foil, a tube or nozzle was fabricated into the 

 foil suction side tip — in close vicinity of the tip vortex attachment point — which 

 enabled water to be injected, downstream, directly into the tip vortex core. The 

 end of the injection nozzle was located at midchord, inboard approximately 0.072 in. 

 (0.00183 m) from the tip, and oriented in a chordwise direction. This tube, with a 

 0.133 in. (0.00338 m) outside diameter, was fitted and faired into a channel which 

 was cut into the surface of the foil tip. Inside the foil, the tube connected to a 

 larger feed-line which extended the entire span of the model. Figure 10 shows a 

 closeup of the active mass injection tip area. 



The active mass injection pumping system consisted of a turbine pump — Aurora, 

 3 

 20 gal/min (0.0751 m /min) at 350 ft (160.7 m) head — a flow meter, relief and con- 

 trol valves, etc. Water was taken from the lower branch of the 24-in. VPWT and 

 pumped to the foil injection nozzel at flow rates ranging from 0.3 to 2.4 gal/min 

 (1.13 X lo~^ to 9.07 X 10"-^ m'^/min). 



MEASURING AND MOUNTING APPARATUS 



The model mounting and measuring apparatus is shown schematically in Figure 5. 

 Photographs of the assembled components are shown in Figure 11. The apparatus bolted 

 to a rectangular mounting plate which fitted flush into the top of the 2-D test sec- 

 tion wall. The models bolted directly to a strain gaged force dynamometer, enclosed 

 in the cylindrical housing, which sensed forces normal and tangential to the foil 

 chord. Also, the roll moment associated with the normal force was measured. The 

 dynamometer, designed to accommodate a maximum normal and tangential force of 1000 

 and 80 lb (4450 to 356 N) , respectively, was supported by bearings which allowed ro- 

 tation about an axis through 40 percent root foil chord — through a series of reduc- 

 tion gears. As shown, the model angle of attack could be changed from outside the 

 tunnel through the use of a handcrank and an extension rod. Model access was ob- 

 tained by lifting the apparatus, as shown in Figure 5, out through the tunnel access 

 hatch. 



14 



