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Significant pressure differences also occur on the lower surface for the tip-launcher case in the 0-30% chord region. Similar results are encountered on both the upper and lower surfaces for BL locations closer to the tip launcher. This result may be indicative of the aerodynamic influence of the tip launcher. With this in mind, the pressure distributions are examined for more inboard BL locations, and noticed a significant influence due to the LE antennae (located at BL154) as far inboard as BL146. This effect is unexpected given how relatively small this component is on the aircraft. Based on this significant influence from a small component, it is hypothesized that small aerodynamic differences between stores can cause significant changes in the flow-field, possibly influencing the occurrence of LCO. This may explain why nearly identical configurations have different LCO flight test results which are not predicted by classical flutter analyses. Lissajous Analysis Figure 6-18 and Figure 6-19 show the set of Lissajous plots (-Cp vs. local displacement from the upper surface of the airfoil at various chord vs. span locations) for the rolling, 8Hz ±0.5°, case, to examine linearity and phase relationships. -Cp is chosen as the dependent variable since it is proportional to lift, and the upper surface of the airfoil is being examined. Local vertical displacement is chosen as the independent variable as opposed to AOA, or some other more typical aerodynamic parameter, due to the fact that as this work continues to more complex motions, i.e. vibration and flutter modes, comparison will be made in a straightforward manner with the same technique. A low-pass filter is applied to the data at 100 Hz to filter out the noise due to turbulence effects. The left-hand side of Figure 6-18 corresponds to the LE of the wing, and the right-hand side corresponds to the TE of the wing. The top of the figures corresponds to the wingtip and the bottom to the root of the wing. The left-hand side of Figure 6-19 corresponds to the same 2-D Lissajous plots seen in Figure 6-18, and the right-hand side corresponds to the 3- 80
D Lissajous plots with time being the third dimension. The red circle in all figures indicates the starting point of the cycle, and the black arrows indicate the direction of rotation. The orientation of the Lissajous plots for the tip-launcher case in Figure 6-18 is slightly different from the clean-wing case seen in Figure 6-9, since the tip-launcher plots include two extra span stations, one on the tip launcher (BL183) and one at 100% span (BL180). However, the overall trends are similar. Most of the plots are circular in nature. Much of the forward portion of the wing exhibits a 90° phase shift. However, upon movement inboard toward the wing root, a more elliptical behavior is seen. Near the transition from counter-clockwise to clockwise rotation on the right portion of the plot, regions of 180° phase shift emerge. The figure-eights and other “odd” shapes are also seen for the tip-launcher case, indicating a continuous phase variation within 1 cycle. These occur most prominently in the tip launcher and LE antennae locations, and along the TE. Figure 6-19 A) and D) are individual Lissajous figures taken at 98% span vs. 44% chord location, which corresponds to the secondary shock region ahead of the primary shock as seen in Figure 6-15 C). In this region, an odd circular shape forms due to the continuous phase variation caused by the formation of this secondary shock, which is due to the tip launcher’s presence. The 3-D plot in C) provides more insight as to how the Cp varies with time. Notably, a loop feature is seen occurring in the last quarter of the cycle. Figure 6-19 B) and E) are individual Lissajous figures taken at 93% span vs. 67% chord location, which corresponds to shock recovery region as seen in Figure 6-16 C). The phase relationship for this figure is close to 45° with some unsteadiness due to the shock transition. The 3-D plot in E) shows a loop feature happening in the last half of the cycle. Figure 6-19 C) and F) are individual Lissajous figures taken at 88% span vs. 70% chord location, which also corresponds to shock recovery region as seen in Figure 81
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TEMPORAL ANALYSIS OF TRANSONIC FLOW
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To Dodjie 3
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TABLE OF CONTENTS ACKNOWLEDGMENTS .
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Summary ...........................
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LIST OF FIGURES Figure page 2-1 F-1
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6-9 Lissajous plots of upper surfac
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6-45 2-D (left column) and 3-D (rig
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incrementally since this capability
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are not sufficient to provide an an
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4. Contribute to the work of others
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Classical aircraft flutter is chara
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Popular methods for finding the sol
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LCO amplitude but not the mechanism
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speed for the particular configurat
Page 29 and 30: Denegri 23 explains the flutter fli
Page 31 and 32: Doublet-lattice Denegri 1, 7,12,13
Page 33 and 34: Batina’s work and uses an F-16 ha
Page 35 and 36: As a result of Denegri’s previous
Page 37 and 38: Figure 2-1. F-16 store stations. Fi
Page 39 and 40: Figure 2-5. Flutter flight test bui
Page 41 and 42: Stokes (RANS) equations on hybrid u
Page 43 and 44: CHAPTER 4 ANALYSIS TECHNIQUES Intro
Page 45 and 46: time-localization cannot be determi
Page 47 and 48: A B C D E Figure 4-3. Analysis of s
Page 49 and 50: (CFD) analyses in order to capture
Page 51 and 52: the appropriate time step for the n
Page 53 and 54: Wing1, is the wing-only (no fuselag
Page 55 and 56: similar to DES but with modificatio
Page 57 and 58: Figure 5-1. Time step comparison of
Page 59 and 60: A B Figure 5-3. Flow results for 8
Page 61 and 62: A B Figure 5-5. Flow results for 8
Page 63 and 64: Figure 5-7. Turbulence model compar
Page 65 and 66: Figure 5-9. CFD vs. wind tunnel com
Page 67 and 68: Figure 5-11. CFD vs. wind tunnel co
Page 69 and 70: Figure 5-13. CFD vs. wind tunnel co
Page 71 and 72: server cluster comprised of 5,120 p
Page 73 and 74: of oscillation. The 88% span locati
Page 75 and 76: since it is proportional to lift, a
Page 77 and 78: of phase. Figure 6-10 B) and D) are
Page 79: The instantaneous Cp measurements p
Page 83 and 84: frequency of 8Hz. The wavelet plot
Page 85 and 86: vortex is observed travelling outbo
Page 87 and 88: near 70% chord and the second near
Page 89 and 90: expected from a lift curve slope. A
Page 91 and 92: shape of this Lissajous is nonlinea
Page 93 and 94: occurring at harmonics, and assumes
Page 95 and 96: the same direction of rotation on t
Page 97 and 98: the roll cycle, and the black arrow
Page 99 and 100: B) shows the fast Fourier transform
Page 101 and 102: is that shock separation aft of the
Page 103 and 104: on the upper surface, a much larger
Page 105 and 106: Figure 6-1. F-16 wing planform with
Page 107 and 108: A C B Figure 6-4. DDES of F-16 in s
Page 109 and 110: Cp (Non-dimensional) Cp (Non-dimens
Page 111 and 112: -Cp (Non-dimensional) A -Cp (Non-di
Page 113 and 114: -Cp (Non-dimensional) A -Cp (Non-di
Page 115 and 116: -Cp (Non-dimensional) A Time (sec)
Page 117 and 118: A B Figure 6-14. DDES-SARC of F-16
Page 121 and 122: Figure 6-18. Lissajous plots of upp
Page 123 and 124: -Cp (Non-dimensional) Frequency (Hz
Page 125 and 126: -Cp (Non-dimensional) A Frequency (
Page 127 and 128: A B Figure 6-24. DDES-SARC of F-16
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Cp (Non-dimensional) Cp (Non-dimens
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-Cp (Non-dimensional) A -Cp (Non-di
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-Cp (Non-dimensional) A -Cp (Non-di
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-Cp (Non-dimensional) A Time (sec)
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A B D Figure 6-40. DDES of F-16 in
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Cp (Non-dimensional) Cp (Non-dimens
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Figure 6-44. Lissajous plots of upp
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A B Figure 6-50. DDES-SARC of F-16
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Figure 6-52. Lissajous plots of upp
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Impact on Future Design of Aircraft
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The size of the Mach=1 iso-surface
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these cases in order to identify th
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15. Dawson, K. S., and Sussinham, J
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41. Thomas, J. P., Dowell, E. H., a
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67. Cunningham, A. M., Jr., and den
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93. Parker, G. H., Maple, R. C., an
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121. Travin, A. K., Shur, M. L., Sp
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