TY - GEN
T1 - 3D computational modeling of stream flow resistance due to large woody debris
AU - Xu, Yuncheng
AU - Liu, Xiaofeng
N1 - Publisher Copyright:
© 2016 Taylor & Francis Group, London.
PY - 2016
Y1 - 2016
N2 - The study of Large Woody Debris (LWD) is very important in the stream restoration practice. Due to the effects of the irregular geometry of LWD and bathymetry, the stream flow around LWD is complex and turbulent. This paper presents a numerical model to deal with the turbulent flow around LWD with complex geometry, and calculates the flow resistance due to LWD in the streams, with the aim to quantify the momentum extraction from the main flow. In order to simplify the case, the LWD used in this study is made of small trees without leaves manufactured by 3D printing technique. They are placed in a small flume, mimicking the LWD in real stream with an approximately rectangular cross-section. In the computational model, free surface is captured due to its importance when the LWD is partially submerged. The simulated free surface is comparable with the surface elevation data measured by a point gauge in the flume. The drag force due to the tree is calculated by the integral of stress as well as the 1D momentum equation for different LWD angles. The velocity coefficient and the water depth coefficient are used to correct and improve the estimation. The comparison between these two methods suggests there might be substantial error in force when the LWD has complex geometry. The simulation results also indicate that the trees with angles to streamwise larger than 45° cause high velocity in nearbank region downstream, while smaller angles result in large slow flow regions in the wake.
AB - The study of Large Woody Debris (LWD) is very important in the stream restoration practice. Due to the effects of the irregular geometry of LWD and bathymetry, the stream flow around LWD is complex and turbulent. This paper presents a numerical model to deal with the turbulent flow around LWD with complex geometry, and calculates the flow resistance due to LWD in the streams, with the aim to quantify the momentum extraction from the main flow. In order to simplify the case, the LWD used in this study is made of small trees without leaves manufactured by 3D printing technique. They are placed in a small flume, mimicking the LWD in real stream with an approximately rectangular cross-section. In the computational model, free surface is captured due to its importance when the LWD is partially submerged. The simulated free surface is comparable with the surface elevation data measured by a point gauge in the flume. The drag force due to the tree is calculated by the integral of stress as well as the 1D momentum equation for different LWD angles. The velocity coefficient and the water depth coefficient are used to correct and improve the estimation. The comparison between these two methods suggests there might be substantial error in force when the LWD has complex geometry. The simulation results also indicate that the trees with angles to streamwise larger than 45° cause high velocity in nearbank region downstream, while smaller angles result in large slow flow regions in the wake.
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U2 - 10.1201/9781315644479-364
DO - 10.1201/9781315644479-364
M3 - Conference contribution
AN - SCOPUS:85015346822
SN - 9781138029132
T3 - River Flow - Proceedings of the International Conference on Fluvial Hydraulics, RIVER FLOW 2016
SP - 2346
EP - 2353
BT - River Flow - Proceedings of the International Conference on Fluvial Hydraulics, RIVER FLOW 2016
A2 - Constantinescu, George
A2 - Garcia, Marcelo
A2 - Hanes, Dan
PB - CRC Press/Balkema
T2 - International Conference on Fluvial Hydraulics, RIVER FLOW 2016
Y2 - 11 July 2016 through 14 July 2016
ER -