학위논문(박사)--서울대학교 대학원 :공과대학 기계항공공학부,2020. 2. 이관중.The wake vortices of an aircraft descend by self-induction that enables a pilot to identify wake locations. A pilot taking off an aircraft can avoid a wake vortex encounter by performing early rotation and flying at or above the climb path of the preceding aircraft. Such an operation results in a situation, in which two wake vortices are present in the air simultaneously in close proximity. Also, there is a possibility of interactions among vortices where runways are parallel so that a pair of vortices from an aircraft moves to another runway due to crosswind. If the interaction between wake vortex pairs induces a rapid dissipation, it may be possible to adjust the take-off separation time and, therefore, in-crease the airport capacity.
In this study, the transport and decay characteristic processes involving interactions between the wake vortex pairs formed by the preceding and following aircraft have been analyzed. The decay processes were ana-lyzed by selecting suitable initial conditions that took into account the high altitude of the following aircraft and the descent of the preceding wake vortices. The high altitude of the following aircraft was included as initial conditions, and atmospheric turbulence conditions were applied to large eddy simulations to account for the vortex core instability and non-linear transport and decay. The obtained results were analyzed to identify the decay characteristic processes that induce the rapid dissipation of the wake vortices and their conditions.
The numerical simulation results were analyzed to identify the decay processes that induce the rapid dissipation of wake vortices such as merging into a single counter-rotating pair, rapid dissipation, and formation of a vortex ring with or without a deformation of the lower vortex pair. The third process could be effectively used to adjust the take-off separation time for increasing the capacity at airports.항공기의 와후류는 자기 유도에 의해 하강하는 특징을 가지기 때문에 그 위치를 식별할 수 있다 . 이륙하는 조종사는 선행 항공기의 이륙 지점 앞에서 이륙하고 선행 항공기의 등반 경로 위로 비행하면 와후류 를 피할 수 있다 . 이러한 회피 비행은 두 개의 와후류 가 동시에 근접하여 대기 중에 존재하는 상황 이 발생할 수 있으며 두 쌍 사이의 거리가 충분히 가까운 경우 상호작용이 발생할 것이다 또한 선행 항공기 에서 발생한 와후류 가 인접 활주로로 이동할 경우 에도 와후류 간의 상호작용이 발생할 수 있다. 본 연구는 선행 항공기와 후행 공기에 의해 생성된 서로 다른 wake vortex pair 간의 상호 작용으로 인해 발생하는 이동 및 소산 특성 프로세스를 수치해석으로 분석하였다. 후행 항공기의 높은 고도는 초기 조건으로 고려되었으며, 와후류 의 불안정성과 비선형 수송 및 붕괴를 설명하기 위해 대기 난류 조건이 수치해석 에 적용되었다 . 해석 결과를 분석하여 단일 와후류 쌍으 로의 합병 , 빠른 소산 , vortex ring 의 형성 이후 하부 vortex pair 를 변형하거나 변형없이 각각 소산하는 프로세스를 확인하였다.Chapter 1. Introduction 1
1.1 Airport capacity and wake vortex 1
1.2 Previous study about wake vortex 7
1.3 Outline of Dissertation 13
Chapter 2. Numerical simulations 14
2.1 Large eddy simulation and computational domain 16
2.1.1 Reynolds averaging 18
2.1.2 Favre (mass) averaging 19
2.1.3 Favre- and Reynolds-Averaged Navier-Stokes Equations 20
2.1.4 Spatial filtering 22
2.1.5 Filtered governing equations 23
2.1.6 Subgrid-scale modeling 25
2.1.7 Numerical scheme 27
2.1.8 Computational grid 32
2.2 Background turbulence field 33
2.2.1 Stochastic Noise Generation and Radiation (SNGR) 34
2.2.2 Artificial External Forcing 35
2.3 Wake vortex initialization 39
2.4 Core line identification and calculations of wake vortex parameters 40
2.5 Validation of numerical methods 43
Chapter 3. Time delay wake vortex interaction 48
3.1 Single Pair of Vortices 51
3.2 Interaction Between Two Pairs of Vortices 55
3.2.1 Light medium wake vortices interaction 55
3.2.2 Medium medium wake vortices interaction 59
3.2.1 Medium heavy wake vortices interaction 62
3.3 Summary of the time delay interaction 64
Chapter 4. Vertical Four Vortex System 66
4.1 Definition of a vertical four-vortex system 66
4.2 V4VS numerical simulation cases 68
4.3 Overall temporal evolutions of V4VS 69
4.3.1 Effect of the vertical distance at a large circulation ratio 71
4.3.2 Effect of the vertical distance at the same circulation 73
4.3.3 Effect of the vertical distance at a small circulation ratio 75
4.4 Criteria for switching between different decay processes 77
4.4.1 Non-linear interactions of the co-rotating pair 79
4.4.2 Two decay processes occurring at a high vertical distance 81
4.4.3 Linking of the upper vortex pair 84
4.5 Four decay processes of V4VS 86
4.5.1 Merging the 1st V4VS characteristic decay process 88
4.5.2 Wrapping the 2nd V4VS characteristic decay process 91
4.5.3 Ring deformation the 3rd V4VS characteristic decay process 94
4.5.4 Parallel ring dissipation the 4th V4VS characteristic decay process 97
4.6 Dissipation effects of various V4VS decay processes 100
4.7 V4VS efficiency assessment for increasing airport efficiency 102
Chapter 5. Conclusion 104
References . 107
Appendix A. deterministic wake vortex model (DVM) [17] 113
Appendix B. Vortex parameters raw data for vertical four vortex interaction cases 115
B.1 Hv05Rg10 116
B.2 Hv10Rg10 117
B.3 Hv15Rg10 118
B.4 Hv20Rg10 119
B.5 Hv25Rg10 120
B.6 Hv30Rg10 121
B.7 Hv05Rg15 122
B.8 Hv10Rg15 123
B.9 Hv15Rg15 124
B.10 Hv20Rg15 125
B.11 Hv25Rg15 126
B.12 Hv30Rg15 127
B.13 Hv05Rg07 128
B.14 Hv10Rg07 129
B.15 Hv15Rg07 130
B.16 Hv20Rg07 131
B.17 Hv25Rg07 132
B.18 Hv30Rg07 133
B.19 Single wake vortex pair at Γ0=530m2/s 134
B.20 Single wake vortex pair at Γ0=360m2/s 135
국문초록 136Docto