1. The successful integration to the right end of the duct allows the iteration to begin on the impedance conditions at x = L. Figures 7-10 depict the variation of the velocity amplitude of each harmonic through the duct for a case where the impedance conditions at x = L are satisfied by the iteration. Several cases were calculated using different reflectlon coefficients to initiate the iteration. In each case the iteration converged to the same solution. Also, the flow i n the vicinity of the throat is i n the near-sonic region. The parameters for each case are identical except for the number of harmonics. These figures illustrate the dominance of the fundamental signal. The fundamental signal i n Fig. 10 computed using four harmonics is not appreciably different from that in Fig. 7 using one harmonic. Also shown i s the rapid increare in the intensity of the disturbance near the throat region. The higher harmonics do not become significant until the throat is approached. signal there i s a reduction of its amplitude at the exit. Including higher harmonics reduces the amplitude of the fundamental signal to a s t i l l lower value at the exit, thus the increased intensity near the throat appears to transfer energy from the fundamental to the higher harmonics. The results of the case using four harmonics were used as input for a case using ten harmonics. performed on this case due to the large computation time that would have been rFquired for ten harmonics. Integration to the exit would be performed to determine ifa singularity would appear that was undetected by using four harmonics. Also the impedance conditions a t x = L were evaluated to determine ifthey were s t i l l satisfied. This example confirms the results of Fig. 10. For the first two harmonics the results are essentially the same as that obtained by using four hamonics in the computation of the solution. The only significant result of this case not shown in Fig. 10 is the reduction of the third and fourth harmonics at the exit due to their interaction with the higher harmonics.
2. Figures 13 and 14 are similar to the two previous figures, but here the reduction i n the intensity of the fundamental signal at the duct exit by increasingp1and bio, respectively, i s shown. Input values for these figures are identical to those used to compute the cases inFigs. 11 and 12.
3. Sonic Block Silencing for Axial and Screw‐Type Compressors
4. Propagation of Sound through a Variable‐Area Duct with a Steady Compressible Flow