Fig. 3. Control and dissipating culvert end flow velocity in FLOW-3D environment at t = 20 s (a) control (b) ALT 1 and (c) ALT 2

FLOW-3D 기반 CFD 수치 시뮬레이션을 이용한 침식 방지용 소멸형 암거 출구 설계

Fig. 3. Control and dissipating culvert end flow velocity in FLOW-3D environment at t = 20 s (a) control (b) ALT 1 and (c) ALT 2
Fig. 3. Control and dissipating culvert end flow velocity in FLOW-3D environment at t = 20 s (a) control (b) ALT 1 and (c) ALT 2

연구 배경 및 목적

문제 정의

  • 고속 유출수가 암거(culvert) 출구에서 발생시키는 하류 침식(erosion)과 세굴(scouring)은 수리공학 분야에서 중요한 문제임.
  • 암거 시스템의 구조적 손상은 유지보수 비용 증가 및 환경적 문제(수생 생물 이동 장애 등)를 유발할 수 있음.
  • 기존 연구들은 암거 출구에서 발생하는 고속 유출수의 운동에너지 감소 방안이 필요함을 강조해왔음.

연구 목적

  • FLOW-3D CFD 모델을 활용하여 새로운 소멸형 암거 출구 설계를 개발 및 분석.
  • 표준 암거(기존 모델)와 두 가지 대체 설계안(ALT 1, ALT 2)의 비교 분석 수행.
  • 유출수의 속도 및 운동에너지를 측정하여 최적의 암거 출구 설계를 도출.

연구 방법

수치 모델 설정 (FLOW-3D 적용)

  • FLOW-3D v11.1.0 사용
  • VOF(Volume of Fluid) 기법을 활용하여 자유 표면 추적
  • 난류 모델: RNG k-ε 난류 모델 사용
  • 격자(cell) 크기: 0.02m, 총 약 250,000개 셀 적용
  • 경계 조건:
    • 유입부: 일정 유량(0.2 m³/s) 적용
    • 유출부: 자유 방출 조건 적용
    • 바닥 및 벽면: 매끄러운 벽면(smooth wall) 처리

실험 검증 및 보정

  • Taha et al. (2020) 실험 데이터를 활용하여 FLOW-3D 모델 보정 및 검증 수행.
  • 암거 상류 수심 데이터(R² > 0.90, RMSE < 1.9 cm)와 비교하여 신뢰성 확보.

분석 대상

  1. 표준 암거 (기본 설계)
  2. 대체 설계 1 (ALT 1)
  3. 대체 설계 2 (ALT 2)

주요 결과

유속 분석

  • 기본 설계 대비 ALT 1 및 ALT 2의 하류 유속 감소 효과 확인.
  • 중심선 유속:
    • 표준 암거: 1.37 m/s
    • ALT 1: 0.83 m/s
    • ALT 2: 0.73 m/s

운동에너지 분석

  • 하류 평균 운동에너지 비교 결과:
    • 표준 암거: 1.37 J/kg²
    • ALT 1: 0.83 J/kg² (약 39% 감소)
    • ALT 2: 0.73 J/kg² (약 47% 감소)

침식 분석 (Sandbox 실험 기반)

  • 침식된 하류 모래 질량 비교:
    • 표준 암거: 9.4 kg 침식
    • ALT 1: 8.3 kg 침식 (약 11.1% 감소)
    • ALT 2: 9.0 kg 침식 (약 4.2% 감소)

결론 및 향후 연구

결론

  • FLOW-3D 기반 수치 해석을 통해 대체 설계(ALT 1, ALT 2)가 기존 암거 출구 대비 침식 및 세굴 저감 효과가 있음을 확인.
  • ALT 1 설계가 상대적으로 운동에너지 및 침식 감소 효과가 더 우수함.
  • FLOW-3D는 암거 출구 설계 최적화 및 침식 저감 대책 수립에 활용 가능함.

향후 연구 방향

  • LES(Large Eddy Simulation) 난류 모델을 활용한 추가 분석.
  • 실제 현장 실험과의 비교 검증을 통한 모델 정밀도 향상.
  • 다양한 유량 및 암거 형상에 대한 추가 연구 수행.

연구의 의의

이 연구는 FLOW-3D를 활용하여 침식 방지용 소멸형 암거 출구 설계를 수치적으로 분석한 최초 연구 중 하나로, 환경 친화적인 암거 설계 및 유지보수 비용 절감에 기여할 수 있는 실질적인 데이터를 제공하였다.

Fig. 1. Plan view of control and alternative dissipating culvert end designs (a) control culvert end plan view (b) alternative dissipating culvert end (ALT 1) plan view and (c) alternative dissipating culvert end (ALT 2) plan view
Fig. 1. Plan view of control and alternative dissipating culvert end designs (a) control culvert end plan view (b) alternative dissipating culvert end (ALT 1) plan view and (c) alternative dissipating culvert end (ALT 2) plan view
Fig. 3. Control and dissipating culvert end flow velocity in FLOW-3D environment at t = 20 s (a) control (b) ALT 1 and (c) ALT 2
Fig. 3. Control and dissipating culvert end flow velocity in FLOW-3D environment at t = 20 s (a) control (b) ALT 1 and (c) ALT 2
Fig. 4. Experimental and simulation results on culvert upstream water depth at different flow rates
Fig. 4. Experimental and simulation results on culvert upstream water depth at different flow rates

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