Fluid Velocity

FLOW-3D를 이용한 교각 주변 국부 세굴 깊이 모델링

연구 배경 및 목적

  • 문제 정의: 교각 주변에서 발생하는 국부 세굴(Local Scour)은 하천 바닥 침식을 유발하여 교량의 구조적 안정성을 위협하는 주요 요인 중 하나이다.
  • 연구 목적:
    • FLOW-3D를 활용한 세굴 모델 개발: CFD(Computational Fluid Dynamics) 기반 수치 모델을 사용하여 교각 주변의 세굴 형상을 예측.
    • 실험 데이터와의 비교: 실험실 실험과 수치 모델의 결과를 비교하여 모델의 신뢰성을 평가.
    • 세굴 깊이 및 유속 패턴 분석: 교각 앞쪽 및 후류에서 형성되는 유동 구조와 세굴의 관계를 분석.

연구 방법

  1. 실험 데이터 수집 및 모델링
    • 실험실 실험:
      • 터키 가지안테프 대학교의 수리 실험실에서 수행.
      • 0.8m × 0.9m 크기의 직사각형 수로에서 직경 10cm의 원형 교각을 배치.
      • 유량 0.048 m³/s, 유속 0.48 m/s, 수심 11cm 설정.
      • 세굴층은 비응집성(non-cohesive) 모래(d₅₀ = 1.45mm)로 구성.
    • FLOW-3D 기반 CFD 모델링:
      • VOF(Volume of Fluid) 기법을 사용하여 자유 수면 모델링.
      • RNG k-ε 난류 모델을 적용하여 난류 흐름 분석.
      • 침식 및 퇴적 모델을 적용하여 하상 변화 예측.
  2. 격자 설정 및 경계 조건
    • 메쉬 독립성 검토: 64,000개 이상의 격자를 사용하여 최적화 수행.
    • 경계 조건:
      • 입구: 일정한 유속(0.48 m/s) 설정.
      • 출구: 자유 유출 조건 적용.
      • 하천 바닥: 이동 가능 침전층(Sediment Bed)으로 설정.

주요 결과

  1. 세굴 깊이 비교
    • 실험 값: 6.9 cm
    • FLOW-3D 예측값: 6.5 cm (실험 대비 오차 10%)
    • 실험과 수치 모델의 결과가 높은 상관관계를 보임.
  2. 유동 및 세굴 패턴 분석
    • 유속 분포:
      • 교각 전면부에서 강한 와류(Horseshoe Vortex) 발생 → 침식 심화.
      • 후류 영역에서는 유속이 감소하며 퇴적 형성.
    • 세굴 형상:
      • 최대 세굴 깊이는 교각 전면부 및 측면에서 발생.
      • FLOW-3D 모델은 세굴 발생 위치 및 심도를 효과적으로 예측.
  3. 시간에 따른 세굴 발전
    • 실험 및 CFD 모델 모두에서 1시간 후 세굴 깊이가 안정화됨.
    • 세굴 속도는 초기 30분 동안 급격히 증가한 후 점진적으로 감소.

결론 및 향후 연구

  • 결론:
    • FLOW-3D 기반 CFD 모델은 교각 주변의 세굴 깊이를 실험 결과와 높은 정확도로 예측할 수 있음.
    • RNG k-ε 난류 모델이 국부 세굴 해석에 적합함을 확인.
    • 세굴 깊이 예측에서 실험 대비 오차는 약 10%로 양호한 결과를 보임.
  • 향후 연구 방향:
    • 더 정교한 난류 모델(예: LES) 적용 및 비교.
    • 다양한 교각 형상 및 유량 조건에서 추가 검증.
    • 인공지능(AI) 및 머신러닝을 활용한 세굴 예측 모델 개발.

연구의 의의

이 연구는 FLOW-3D를 이용한 국부 세굴 예측의 신뢰성을 검증하고, 교량 설계 및 유지보수 전략 수립에 활용될 수 있는 중요한 기초 데이터를 제공한다.

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