Title Page
Abstract
Contents
Nomenclature 11
Chapter 1. Introduction 17
1.1. Inflight icing and simulation 17
1.2. Issues in inflight icing simulation 20
1.2.1. Unsteady effect owing to body motion 21
1.2.2. Surface roughness growth 24
1.2.3. Laminar-turbulence transition due to surface roughness 27
1.3. Motivation and scope of the dissertation 28
Chapter 2. Backgrounds for inflight icing and simulation 32
2.1. Icing scenario 32
2.1.1. Icing clouds 35
2.1.2. Icing envelope 36
2.1.3. Parameters for inflight icing 39
2.1.4. Classification of ice shapes 42
2.2. Numerical simulation for inflight icing 46
2.2.1. Aerodynamic module 48
2.2.2. Droplet impingement module 50
2.2.3. Thermodynamic module 51
2.2.4. Ice growth module 53
2.3. ICEPAC 54
Chapter 3. Quasi-unsteady ice accretion solver 58
3.1. Alternative approaches 59
3.1.1. Analytical methods 59
3.1.2. Loose coupling methods - averaged airflow with icing analysis 61
3.1.3. Loose coupling methods - Applying RANS solver 63
3.1.4. Quasi-steady approach for moving body 65
3.2. Quasi-unsteady ice accretion solver 69
3.2.1. Concept of quasi-unsteady ice accretion solver 69
3.2.2. Implementation of quasi-unsteady ice accretion solver to ICEPAC 72
3.2.3. Quasi-steady ice accretion solver for an oscillating airfoil 79
Chapter 4. Physics based roughness modeling 81
4.1. Physics in roughness development 83
4.2. Alternative approaches 86
4.2.1. Multizone model 86
4.2.2. Empirical roughness distribution model 87
4.2.3. Physics based roughness distribution model 88
4.3. Local surface roughness modeling 90
4.3.1. Maximum bead height 90
4.3.2. Water film behavior 92
4.3.3. Implementation of roughness model in ICEPAC 94
Chapter 5. Roughness induced transition model 96
5.1. Alternative approaches 97
5.1.1. 1st generation icing code with inviscid flow solver[이미지참조] 97
5.1.2. 2nd generation icing code with RANS equation[이미지참조] 98
5.2. Roughness induced transition modeling 100
5.2.1. Roughness amplification parameter, Ar[이미지참조] 100
5.2.2. Modifying turbulence model 102
5.2.3. Applying model to in-flight icing code 106
Chapter 6. Verification and validation 108
6.1. Quasi-unsteady approach 108
6.1.1. Oscillating NACA 0015 airfoil with a smooth surface 109
6.1.2. Oscillating S809 airfoil with leading-edge roughness 111
6.1.3. Collection efficiency of the oscillating airfoil 115
6.2. Laminar-turbulent transition 118
6.2.1. Flat plate case 118
6.2.2. Airfoil with roughness of leading edge 121
6.3. Roughness distribution model 123
6.3.1. Roughness height comparison 123
Chapter 7. Application: Icing on fixed airfoil 128
7.1. Roughness distribution and laminar-turbulent transition 128
7.2. Effect on roughness and transition model on ice shape 132
Chapter 8. Application: Icing on oscillating airfoil 145
8.1. Effect of oscillating frequency on icing solvers 147
8.1.1. Convective heat transfer 148
8.1.2. Collection efficiency 152
8.1.3. Water film thickness 154
8.2. Effect of roughness on oscillating airfoil icing 156
8.3. Ice shape comparison 161
Chapter 9. Conclusion and Future Works 165
References 171
국문 초록 187
Table 1. Time and cost requirement for inflight icing tests 18
Table 2. Characteristics of clouds 33
Table 3. Generation of inflight icing code 49
Table 4. Verification and validation case for quasi-unsteady approach 109
Table 5. Summary of roughness-related characteristics 121
Table 6. Validation cases for surface roughness 123
Table 7. Rough-smooth zone transition location and ice/impinging limit 125
Table 8. Transition onset and transitional region length 129
Table 9. Validation cases for shapes of ice 132
Table 10. Parameters for the experiments of Boeing-NASA consortium 145
Table 11. Time step selection for icing simulation for oscillating airfoil 146
Table 12. Distance of impinging limit from leading edge at upper surface 151
Table 13. Distance of impinging limit from leading edge at upper surface 152
Fig. 1. Cloud Classification 34
Fig. 2. Continuous Maximum (Stratiform Clouds) Atmospheric Icing Conditions 37
Fig. 3. Intermittent Maximum (Cumuliform Clouds) Atmospheric Icing Conditions 37
Fig. 4. Natural Probabilities for LWC Averages at Altitudes up to 2500 ft above ground level (AGL) 39
Fig. 5. Feature of Rime Ice 43
Fig. 6. Feature of Glaze Ice 44
Fig. 7. Feature of Mixed Ice 45
Fig. 8. Structure of general inflight icing code 47
Fig. 9. Overall procedure of ICEPAC 55
Fig. 10. Analysis of performance degradation due to icing on the rotorblade 60
Fig. 11. Procedure for rotorcraft icing performance analysis proposed by Britton 61
Fig. 12. Procedure for ice shape prediction via loose coupling CFD method 64
Fig. 13. Comparison of the ice shape for oscilltiating airfoil at different frequency 66
Fig. 14. Characterization of the oscillating motion into discretized angle of attack 68
Fig. 15. Procedure for predicting ice on oscillating airfoil via quasi-unsteady approach 71
Fig. 16. Quasi-unsteady approach for the icing analysis of an oscillating airfoil 75
Fig. 17. Hybrid grid for oscillating airfoil simulation 78
Fig. 18. Quasi-steady approach for the icing analysis of an oscillating airfoil 80
Fig. 19. Simplified roughness growth process according to bead formation 85
Fig. 20. Schematic view of the spherical bead geometry 91
Fig. 21. Implementation of physics based roughness model on ICEPAC 95
Fig. 22. Implementation of the roughness-induced transition model in ICEPAC 103
Fig. 23. Comparison between the aerodynamic coefficients of an oscillating airfoil and a smooth surface 110
Fig. 24. Comparison between the aerodynamic coefficients of an oscillating airfoil with leading-edge roughness 112
Fig. 25. Verification of the droplet impingement module for the quasi-steady and quasi-unsteady solver 116
Fig. 26. Zero-gradient flat plate case (Rex=1,300,000)[이미지참조] 118
Fig. 27. Coefficients of skin friction for zero-gradient flat plate 120
Fig. 28. Integrated intermittency for partially roughened NACA0012 122
Fig. 29. Comparison of heights of surface roughness 124
Fig. 30. Comparison of heat transfer coefficients 130
Fig. 31. Ice shape compared with the NASA IRT cases 136
Fig. 32. Shape analysis for cases of mixed ice 141
Fig. 33. hcv for case 1 (V∞=102.8 m/s, T∞=-11.11℃, LWC=0.55 g/㎥, MVD=20 µm)[이미지참조] 143
Fig. 34. Convective heat transfer coefficient for different oscillating frequencies and steady state assumption 149
Fig. 35. γ (intermittency) distribution for different oscillating frequencies and steady state assumption 150
Fig. 36. Collection efficiency for different oscillating frequencies and steady state assumption 153
Fig. 37. Water film thickness for different oscillating frequencies and steady state assumption 155
Fig. 38. Ice shapes for different roughness heights 158
Fig. 39. Ratio for the empirical roughness height according to the reduced frequency 159
Fig. 40. Comparison between the ice shapes on oscillating airfoils 163