한국농림기상학회지, 제 11권 제4호(2009) (pISSN 1229-5671, eISSN 2288-1859)
Korean Journal of Agricultural and Forest Meteorology, Vol. 11, No. 4, (2009), pp. 192~205
DOI: 10.5532/KJAFM.2009.11.4.192
ⓒ Author(s) 2014. CC Attribution 3.0 License.


계산유체역학모형 CFD_NIMR_SNU를 이용한 국지적으로
가열된 산악지역의 상세 바람 흐름 모사
−화왕산 산불 사례 −

구해정, 최영진, 김규랑, 변재영
국립기상연구소 응용기상연구과

(2009년 10월 26일 접수; 2009년 12월 16일 수정; 2009년 12월 16일 수락)

Simulation of Detailed Wind Flow over a Locally Heated Mountain
Area Using a Computational Fluid Dynamics Model,
CFD_NIMR_SNU
– a fire case at Mt. Hwawang –

Hae-Jung Koo, Young-Jean Choi, Kyu Rang Kim, Jae-Young Byon
Meteorological Application Research Laboratory, National Institute of Meteorological Research,
KMA, 45 Gisangcheong-gil, Dongjak-gu, Seoul, 156-720, Republic of Korea

(Received October 26, 2009; Revised December 16, 2009; Accepted December 16, 2009)

ABSTRACT
The unexpected wind over the Mt. Hwawang on 9 February 2009 was deadly when many spectators were watching a traditional event to burn dried grasses and the fire went out of control due to the wind. We analyzed the fatal wind based on wind flow simulations over a digitized complex terrain of the mountain with a localized heating area using a three dimensional computational fluid dynamics model, CFD_NIMR_SNU (Computational Fluid Dynamics_National Institute of Meteorological Research_Seoul National University). Three levels of fire intensity were simulated: no fire, 300oC and 600oC of surface temperature at the site on fire. The surface heat accelerated vertical wind speed by as much as 0.7 m s-1 (for 300oC) and 1.1 m s-1 (for 600oC) at the center of the fire. Turbulent kinetic energy was increased by the heat itself and by the increased mechanical force, which in turn was generated by the thermal convection. The heating together with the complex terrain and strong boundary wind induced the unexpected high wind conditions with turbulence at the mountain. The CFD_NIMR_SNU model provided valuable analysis data to understand the consequences of the fatal mountain fire. It is suggested that the place of fire was calm at the time of the fire setting due to the elevated terrain of the windward side. The suppression of wind was easily reversed when there was fire, which caused updraft of hot air by the fire and the strong boundary wind. The strong boundary wind in conjunction with the fire event caused the strong turbulence, resulting in many fire casualties. The model can be utilized in turbulence forecasting over a small area due to surface fire in conjunction with a mesoscale weather model to help fire prevention at the field.

Keyword: CFD, Turbulence, TKE, Mountain fire

MAIN

적요

2009년 2월 9일 화왕산에서는 대보름 행사인 ‘억새 태우기’가 많은 사람들이 지켜보는 가운데 시작되었지만 예상하지 못한 강풍으로 산불로 확대되어 많은 인명피해가 발생하였다. 본 연구에서는 3차원 계산 유체역학 모형인 CFD_NIMR_SNU 모형을 이용하여 복잡한 산악지역에서 국지적 가열에 따른 바람장을 모사함으로써 이날 발생한 산악 화재의 특성을 분석하였다. 화재가 발생한 지역의 지표 온도는 가열이 없을 때, 300oC 및 600oC 일 때의 3가지 가열 강도조건을 주어 모사하였다. 지표 가열은 화재 발생 지역 중앙에서 수직 바람장을 0.7m s-1(300oC)와 1.1m s-1(600oC)만큼 증가시켰다. 난류운동에너지는 화재의 열에너지 자체 및 열적 순환에 의해 증가된 운동에너지에 의해 증가하였다. 화재로 인한 열은 복잡한 지형과 강한 경계 바람 조건과 함께 화왕산의 예상하지 못한 난류와 강풍 조건을 유도하였다. CFD_NIMR_SNU 모형은 인명피해를 발생시킨 산불을 이해하는데 도움이 되는 귀중한 분석 자료를 제공하였다. 모사 결과에 따르면 화재 발생 지점은 풍상측의 높은 지형으로 인하여 화재 발생 직전까지는 바람이 거의 억제되었던 것으로 보인다. 이러한 바람의 억제는 화재 발생에 따른 뜨거운 공기의 상승과 강한 경계 바람 조건에 의해 쉽게 되돌려졌다. 즉, 강한 경계 바람과 화재로 인한 가열이 함께 작용하여 강한 난류가 만들어졌고, 여러 명의 사상자가 발생한 산악 화재로 확산되었던 것이다. CFD_NIMR_SNU 모형은 중규모 모형과의 결합을 통하여 좁은 영역의 화재로 인한 난류 예보를 생산하는 등 산불 예방을 위해 활용될 수 있을 것이다.

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