eight test positions and the alinement was checked by the pressure balance technique. 

 A Preston tube using a 0.072-in. (1.83-nim) inside diameter was attached and alined 

 with the flow at the pressure taps to measure the shear stress. The Preston tube 



was calibrated in a 1-in. (2.54-cm) diameter water-pipe flow facility described 



9 

 by Huang and von Kerczek. These pressure taps were connected to a multiple pres- 

 sure scanivalve system that takes one integral pressure transducer with its zeroing 

 circuit and measures a single pressure in sequence along the stern upper meridian. 



The pressure transducer was designed for measuring low pressures of up to 1 psi 



_3 

 (6.895 X 10 Pa). The zero-drift linearity, scanivalve hysteresis, and pressure 



transducer zeroing circuit were carefully checked and the overall accuracy was found 



to be within 0.5 percent of the dynamic pressure. 



The mean axial and radial velocities and the turbulence intensities for the 

 Reynolds stress calculations were measured by a TSI, Inc. Model 1241-20 "X" type 

 hot-film probe. The probe elements are 0.002 in. (0.05 mm) in diameter with a 

 sensing length of 0.04 in. (1.0 mm). The spacing between the two cross elements is 

 0.04 in. (1.0 mm). A typical schematic of the hot-film probe used is shown in 

 Figure 5. A two-channel hot-wire and hot-film anemometer with linear izers was used 

 to monitor the response of the hot-film probe. A temperature compensating sensor 

 (probe) was used with each hot-film element to regulate the operating temperature of 

 the sensor with changes in air temperature. The "X" hot film and its temperature- 

 compensated sensor were calibrated together through the expected air temperature- 

 range and supplied with their individual linearization polynomial coefficients at 

 the factory. 



The frequency response of the anemometer system, for reliable measurements 

 claimed by the manufacturer, is to 100 kHz. Calibration of the "X" hot film was 

 made before and after each set of measurements. It was found that the hot-film 

 anemometer system had a +0'5 percent accuracy, +0.75 ft/sec (+0.23 m/s) accuracy 

 at the free-stream velocity of 150 ft/sec (45.72 m/s), during the entire experiment. 

 An estimate was made of the crossflow velocity by yawing the "X" hot-film probe in 

 the free stream. It was found that the crossflow velocities were about one percent 

 of the free-stream velocity. 



The linearized signals were fed into a Time/Data Model 1923-C real-time 

 analyzer. Both channels of the analog signal were digitized at a rate of 128 points 



