coefficient. The dashed curve, denoted by potential flow theory, represents the 

 predictions of the XYZ potential flow method of Dawson and Dean before using the 

 displacement body concept. The solid curve shows C on the displacement body after 

 one iteration of the displacement body procedure. The computed pressure coefficient 

 is 



S-^-l^' "^ 



where U is the computed potential flow velocity on the displacement body and U is 

 the free-stream velocity, 100 ft/sec (30.48 m/s). 



Two results are immediately apparent from the comparisons given in Figure 6. 

 First, the theory was not able to predict accurately the values of the pressure 

 coefficient for x/L > 0.93. At these locations, the boundary layer is much thicker 

 than the body cross section and theoretical displacement thicknesses were not 

 available due to premature abortion of the computer code calculation in the separa- 

 tion region. Second, the predictions using the displacement body concept agree 

 more closely with the measured values than do the data denoted as potential flow. 

 After one iteration of the displacement procedure, overall agreement between 

 theoretical and measured values of the pressure coefficient is considered good even 

 though the predicted values are slightly lower than the measured values. No further 

 iterations of the displacement method have been implemented at present. Further 

 refinement of the three-dimensional wake and near wake region by the displacement 

 body conception should improve the accuracy of the theoretical prediction. 



MEAN VELOCITY PROFILES 



Mean velocity measurements were taken with an "X" hot-film sensor which was 



stepped away from the body in the n direction. Measurements of velocity in the 



axial X and normal n directions, u and v , respectively, were taken with the 

 e X n 



probe elements alined vertically. The sensor elements were rotated 90 degrees to 

 the horizontal position to measure the mean velocity w„ in the direction. An 

 on-line computer was used to collect data at a sample rate of 1024 data values in 

 8 sec. 



11 



