- 205 - 



[F.4] 



(c'+iq')v-« = k [jQ(kD) sin 



N 

 + y (a sin(n+l)e - b cos (n+1) g) Tri"''""'"j , (kD) 

 n=l " " "+1 



N 



+ I {h cos(n-l)6 - a sin (n-1) 6) TTi'^~-'"j , (kD) ] 

 ^, n n n-1 



n=l 



for some frequency 6. The cross-spectral density for the signals of 

 two perpendicular differential pressure gauges is: 



, CF.5D 



(c'+iq')^ ^ ^ — ^- J2^^°^ ^^" 23 

 X y 



N 



+ I (?-^ sin{n+2)B-b^ cos (n+2) g) Tri'^"^^J^_^2 (^D) 

 n=l 



N 

 - I Ca^ sin(n-2)B-b cos (n-2) g) iri'^'^J _2 (kD) ] 

 n=l ^ 



For the configuration of the DPG prototype, five 

 non-ambiguous cross-correlations are possible. This suggests that 

 the first five directional Fourier coefficient pairs (first eleven 

 coefficients) could be developed from Equations F.2 through F.5. 

 Five additional ambiguous cross-correlations are possible so that 

 these eleven coefficients might be better fit by least squares 

 analysis. If the configuration of the DPG arms was altered such that 

 the angle between each of the arms was unique, it is theoretically 



