상류유량 변화에 대한 교량주변 월류 및 압력흐름 3차원 수치모의

초록

A three-dimensional numerical model based on the RANS equations was developed to investigate the hydraulic characteristics of overtopping and pressure flow around bridge structures under extreme hydrologic conditions. The free surface was treated using the density function method, and turbulence closure was achieved with a nonlinear k-ε turbulence model. Numerical simulations revealed that, under overtopping conditions, the upstream velocity decreased due to the backwater effect, while the maximum flow velocity induced by overtopping reached approximately Uover,max/U0=2.0. For pressure flow, the maximum velocity ranged from Upressue,max/ U0=1.8-2.7. As the upstream discharge increased, the difference in water depth between the upstream and downstream became larger, leading to the development of strong shear layers and recirculation zones downstream of the bridge, accompanied by significant free-surface fluctuations. An increase in Δh caused both the mean velocity ratio (U/U0) and high turbulent kinetic energy zones (TKE/TKE0) to expand. For the submerged-orifice type of pressure flow, the maximum velocity was predicted as Upressue,max/U0=2.7. As the flow transitioned to overtopping, Δh/h0=0.15-0.48 resulted in an overtopping discharge ratio of 22%-37%. The results demonstrated that flow type transitions around bridges significantly alter shear and turbulence structures, which are closely related to local scour and hydraulic stability. This study provides three-dimensional insights into bridge hydraulics under extreme flow conditions and offers fundamental hydraulic data that can support future bridge design and maintenance for flood-safety assessment.

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