準超越 空洞 프로펠러 周圍의 空洞 流動 解析 = Analysis of the cavitating flow around trans-cavitating marine propellers

다국어 초록 (Multilingual Abstract)

As the loading on blades of a marine propeller increases, cavitation plays an important role in th unsteady hull forces and also causes severe noise and vibration problems at the stern.
In order to control these problems at the stern of a ship and also to design a propeller with a sufficient but not excessive cavitation margin, it is desirable to predict the extent and behavior of the cavity on the surface of the propeller blades with and improved accuracy.
Recently, there are many ships, of which speed is too slow for super-cavitating propeller, yet too fast for sub-cavitating propeller. In this transient range of this ship speed, conventional propellers have mostly been used till now, for which airfoil sections are adopted along the whole radial position of the blade. However, even for fast ship propellers, local relative velocities along the blades are very different according to the radial positions. That is, the relative cavitation number near the hub is too big for super-cavitation and yet near the blade tip is too small for sub-cavitation.
Propellers for ships in medium speed range always suffers from the super-cavitation in the outer radii of the blade whereas the blade in the inner radii dose not cavitate at all. To solve this problem, Yim developed a so-called trans-cavitating propeller(TCP), which has the super-cavitating wedge-type section near the tip and the sbu-cavitating airfoil-type section near the hub.
The purpose of this thesis is to develop a tool for the analysis of the cavitating flow around trans-cavitation theory was applied in order to analyze the performance of the 2-dimensional foils. The numerical results correlated very well with experimental data.
Two trans-cavitating propellers, manufactured and tasted in KRISO, are selected to validate the lifting surface procedure. For a TCP with a Johnson's five term section, the comparison between the numerical prediction and experiments in fairly good and promising.
The comparison, for the second TCP with the drastic geometric variation near the trailing edge of the wedge-type section, is not satisfactory, due to the lack of numerical convergence.
The new lifting surface procedure, developed and validated with 2-D foils and a TCP, is Generally considered applicable to the practical design of the trans-cavitating propeller with Johnson's five tern section, but needs further refinements to correctly reflect the rapid change of the geometry in the chordwise direction.

목차 (Table of Contents)

• 목차
• Nomenclature = iii
• List of Figures = xi
• 1. 서언 = 1
• 2. 경계치 문제의 정식화 = 8
• 2.1 기본가정 = 8
• 2.2 지배방적식 및 경계 조건 = 10
• 2.3 특이점 분포법 =13
• 2.4 특이점 분포법 = 15
• 2.5 유기속도 계산 = 21
• 2.6 프로펠러 기하학 = 23
• 2.7 후연 반류면의 기하학 = 27
• 2.8 날개에서의 힘과 모멘트 계산 = 29
• 3. 2차원 날개 주위의 공동 유동 = 32
• 3.1 2차원 정상 공동 수중익 문제의 경계치 문제 = 32
• 3.2 2차원 정상 공동 수중익 문제의 수치 정식화 = 34
• 3.3. Lighthill의 수정법 적용에 의한 섭동 속도의 수정 = 38
• 3.4 2차원 정상 공동 수중익의 수치 해석 결과 = 41
• 4. 준초월 공동 프로펠러 주위의 유동해석 = 77
• 4.1 프로펠러 날개의 이산화 = 77
• 4.2 프로펠러 표면에서의 운동학적 경계 조건 = 80
• 4.3 공동 표면에서의 운동학적 경계 조건 = 85
• 4.4 공동 마감 조건 = 89
• 4.5 공동 표면에서의 동역학적 경계조건 = 94
• 4.6 준초월 공동 프로펠러의 기하학 = 100
• 4.7 준초월 공동 프로펠러의 수치해석 결과 = 103
• 5. 결언 = 115
• 참고문헌 = 117
• 부록A. 날개 앞날에서의 특이함수 거동 = 123
• B. Lighthill 수정법 = 125
• Abstract = 126