URANS와 DES 모형을 이용한 만곡개수로에서의 난류흐름 수치모의

국문 초록 (Abstract)

본 연구에서는 만곡개수로에서 발생하는 나선형 흐름구조의 이차류의 특 징으로 분석하기 위해 3차원 수치모의를 수행하였다. 수치모의 대상으로는 Siebert (1982)의 연속만곡수로와 실험 조건을 적용하였으며 난류 모형으로 는 하이브리드 RANS/LES 기법 종류 중 하나인 IDDES와  SST 난 류 모델을 통하여 발생하는 난류를 해석하였다. 격자의 구조에 따른 모델 의 난류 해석을 보기 위해  SST 난류모델은 늘림 격자 구조와 균일 격자 구조에 따른 수치모의를 수행하였고 IDDES 난류모델은 늘림 격자 구조에서 수치모의를 진행하였다. 또한 VOF기법을 적용하여 자유수면 변 동을 해석하였다. 수치모의의 적용성을 확인하기 위해 기존의 연구 Siebert (1982)의 수리 실험값과 Stoesser et al. (2010)의 RANS와 LES 난류모델 을 통한 수치모의 값과의 비교를 통해 보였다. 자유수면을 고려하여 수치 모의를 진행한 IDDES와  SST 모델 모두 최대 유속의 분포는 개수로 특징인 수면 근처에서 형성되는 것을 볼 수 있었으나 IDDES 모델의 경우 시간 평균의 부족으로 인한 결과를 보였다.  SST모델의 경우 수면 근 처에서의 이차류 해석에 있어 RANS 모델과 유사하게 해석되는 것을 보였 으며 수리 실험값과 유사한 LES 모델에 비해 부정확한 모습을 보였다. 전 반적인 이차류의 해석에 있어  SST의 균일 구조 격자가 늘림 격자 구조보다 좀 더 나은 해석 값을 보이지만 절대적인 격자의 차이로 인해 발 생하는 원인으로 보이며 추가적인 실험을 통해 정확한 비교가 필요하다. 또한 잠긴수제로 인한 이차류 저감 효과를 수치모의를 통해 수행하였으며 Park et al. (2019)의 90° 만곡수로 형상과 잠긴수제 재원 및 설치구간을 수치모의 대상으로 적용하였다. 잠긴수제의 설치를 통해 하상에서의 흐름 은 잠긴수제 설치 전에 비해 수로의 중앙으로 이동하는 것을 볼 수 있었으 며 잠긴수제 주변에서 복잡한 흐름을 보였다. 잠긴수제 설치 전 수로의 만 곡부 단면에서의 이차류는 만곡부 외측에 강하게 형성되는 것을 보였나 잠 긴수제를 설치 후 만곡부 이차류가 수로 중앙으로 분포되며 바닥이 아닌 중앙수심에서 형성되는 것을 보였다. 만곡부 외측의 흐름방향 유속 또한 저감되는 효과를 보았다. 결과적으로 잠긴수제의 설치로 인한 이차류의 형 성과 흐름방향 유속의 변화는 만곡부 외측의 하상에 안정에 영향을 미칠 것으로 보인다.

목차 (Table of Contents)

• 차 례
• 국문 요약 ·································································································· Ⅰ
• Abstract ·································································································· Ⅲ
• 표 차례 ········································································································ Ⅴ
• 그림 차례 ···································································································· Ⅵ
• 제 1 장 서 론 ································································································1
• 1.1 연구 배경 및 목적 ···················································································1
• 1.2 연구 내용 ···································································································2
• 1.3 연구 동향 ···································································································3
• 1.3.1 만곡 수로 ························································································3
• 1.3.2 수중 수제 ························································································6
• 제 2 장 수치해석 방법 ························································································7
• 2.1 지배 방정식·······························································································7
• 2.2 VOF 기법 ··································································································8
• 2.3 난류 모델 ·································································································10
• 2.3.1  SST ·····················································································11
• 2.3.2 IDDES ···························································································13
• 2.4 수치모의프로그램 ···················································································16
• 제 3장 연속만곡수로 ··························································································17
• 3.1 수치 모형 적용 ·······················································································17
• 3.2 계산 격자 조건 ·······················································································18
• 3,2.1  SST ·····················································································19
• 3.2.2 IDDES ···························································································20
• 3.3 수치 기법 및 경계조건 ·······································································21
• 3.3.1  SST ···················································································21
• 3.3.2 IDDES ·························································································23
• 3.4 수치해석 결과 및 분석 ·······································································24
• 제 4 장 90° 만곡수로에서 잠긴수제 설치에 따른 이차류 변화 ·······36
• 4.1 수리 모형 실험 ···················································································36
• 4.1.1 하상 적용 ······················································································36
• 4.1.2 격자 구성 ····················································································37
• 4.2 수치 기법 및 경계조건 ·······································································39
• 4.2.1 수치기법 ························································································39
• 4.2.2 경계조건 ························································································39
• 4.3 수치해석 결과 ·······················································································41
• 제 5 장 결론 ·········································································································44
• 5.1 연속만곡수로 ·························································································44
• 5.2 90° 만곡수로에서 잠긴수제 설치에 따른 이차류 변화 ···············45
• 참고문헌 ·············································································································· 46