tailieunhanh - UNSTEADY AERODYNAMICS, AEROACOUSTICS AND AEROELASTICITY OF TURBOMACHINES Episode 6

Tham khảo tài liệu 'unsteady aerodynamics, aeroacoustics and aeroelasticity of turbomachines episode 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 254 Figure 1. Comparison of the lift coefficient for different hub-tip ratios. Mo Mn Mr and Ũ 3n n 0 Upstream r 0 Downstream n l Upstream n 1 Downstream Cuts Or Figure 2. Comparison of the upstream and downstream acoustic coefficients for different hub-tip ratios. Mo Mn Mr and ữ 3n Interaction of Acoustic and Vortical Disturbances with an Annular Cascade 255 Effect of Mean Flow Variation on the Scattering In a swirling mean fbw various radial profiles can be obtained by considering different combinations of free vortex and rigid body swirl. To illustrate how the radial variation of the mean ft w changes the aeroacoustic response we consider four different mean ft ws with the same total Mach number of at the mean radius. The first mean ft w is axial and uniform. The three swirling ft ws have the same axial and swirl Mach numbers of and respectively at the mean radius and consist of a free vortex swirl distribution with Mr a rigid body swirl with Mq and a combination of free vortex and rigid body swirl Mr and Mq . The c rm ratio at the mean radius is ũ 3n mg B 16 V 24 rh rt and a grid of nx X ng X nr 161 X 21 X 21 is used. The gust radial component ur 0 and its upwash a u 1. For the uniform ft w only one propagating acoustic mode -8 0 exists while two propagating modes -8 0 -8 1 exist for the three swirling ft ws. Figure 3 compares the absolute value of the unsteady lift coefficient along the span for the different mean ft ws. The figure shows significant difference in the value and variation trend between the uniform ft w case and the swirling ft w cases indicating that the swirl effect significantly modifies the unsteady lift. The differences in the lift coefficient of the three swirling ft ws are not significant. We now examine the magnitude of the upstream and downstream acoustic coefficients presented in Table 1 . The table shows that the downstream acoustic coefficients are larger than .

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