and computed (by displacement-body model) values of C is, in general, less 



than O.Ol which is about the accuracy of the measurement. The measured 



values of C are tabulated in Table 3. 

 P 

 As will be seen later, the displacement body of Afterbody 5 is convex 



from the parallel middle body up to x/L = 0.898 and becomes concave down- 

 stream from x/L > 0.90, which is rather close to the inflection point of 

 the actual body (x/L = 0.913). The differences in the theoretical values 

 of off-body pressure distributions computed from the displacement body and 

 the actual body are very noticeable at x/L = 0.951 where the measured 

 pressure distributions agree rather well with the distributions computed 

 from the displacement-body model. The close agreement between the computed 

 displacement-body and measured static pressure distributions for Afterbody 

 5, as well as Afterbodies 1 and 2 (Reference 1), support the displacement- 

 body concept for computing the potential flow outside of the displacement 

 surface. The pressure coefficients inside the displacement body may be 



more accurately calculated by a streamline curvature method proposed by 



12 

 Dyne. However, in the present calculation method the value of C is 



assumed to be constant inside the displacement body. The maximum error of 



the value of C from this approximation is less than 2 percent inside the 



displacement body (Figure 6) , 



MEASURED AND COMPUTED MEAN VELOCITY PROFILE 

 MEASUREMENT 



The axial and radial mean velocity components were measured by the 

 "X" hot-film sensor. At a given axial location, measurements were taken 

 at numerous radial positions to obtain the velocity profile. The hot-film 

 probe was mounted with the sensing elements in a vertical position. At 

 each radial position, 1024 data values were collected in 8 seconds. The 

 linearized data were input to a computer code which calculated and printed 

 the values of the mean velocity components u in the axial direction and 

 v in the radial direction (given in Table 4). 



A single element hot-wire sensor also was used to compare with the 

 results of the "X" sensor. The values of the axial mean velocity component 



17 



