TY - GEN
T1 - Methods for predicting vertical velocity distributions in open channel flows with submerged rigid vegetation
AU - Tang, Xiaonan
N1 - Publisher Copyright:
© Proceeding of the 21st LAHR-APD Congress 2018. All rights reserved.
PY - 2018/9/1
Y1 - 2018/9/1
N2 - This paper evaluates the four analytical models of Klopstra, Defina, Baptist, and Nepf model for predicting vertical velocity distributions of flow in an open channel with submerged rigid vegetation, in order to examine their sensibility to vegetation density and submergence ratios (H/h), where H is flow depth and h is vegetation height. Fourteen experimental datasets used cover the ratios of H/h =1.25 ∼ 3.33, and various vegetation density of a =1.1 ∼ 18.5 m-1 (a defined as the frontal areas of the vegetation per unit volume). For submerged vegetated flow, the vertical velocity distribution can often be described by two layers, the vegetation layer in the lower part and the non-vegetation layer in the upper part. The vegetation retards flow by exerting drag force on the flow, thus resulting in different velocities between the vegetation layer and the upper surface layer. Based on an eddy mixing-layer analogy, different analytical models have been proposed for predicting vertical velocity distribution in the two layers, and four models were chosen to examine their sensibility when tested against different independent datasets from those used in their original papers. Our studies show that the four models can predict reasonably well under a certain range of vegetation density and submergence, and that the prediction of all the models are less sensitive in the lower region. The studies also reveal that under the same submergence, the predictions of the four models in the upper layer are less sensitive to low vegetation density (e.g. ah <1) than to high vegetation density (ah >1), but that for the same vegetation density, all four models are much sensitive to the vegetation submergence ratio (H/h). It was also found that the Defina and Klopstra models are almost the same despite some simplification made in the Klopstra model, if the same mixing length scale of eddies (A,)is used. Finally, close examination on A, in the analytical models, and it was found that the predictions of the models (the Baptist, Defina and Klopstra models) are less sensitive to the vegetation density and submergence when A, is evaluated by 0.02√Hh.
AB - This paper evaluates the four analytical models of Klopstra, Defina, Baptist, and Nepf model for predicting vertical velocity distributions of flow in an open channel with submerged rigid vegetation, in order to examine their sensibility to vegetation density and submergence ratios (H/h), where H is flow depth and h is vegetation height. Fourteen experimental datasets used cover the ratios of H/h =1.25 ∼ 3.33, and various vegetation density of a =1.1 ∼ 18.5 m-1 (a defined as the frontal areas of the vegetation per unit volume). For submerged vegetated flow, the vertical velocity distribution can often be described by two layers, the vegetation layer in the lower part and the non-vegetation layer in the upper part. The vegetation retards flow by exerting drag force on the flow, thus resulting in different velocities between the vegetation layer and the upper surface layer. Based on an eddy mixing-layer analogy, different analytical models have been proposed for predicting vertical velocity distribution in the two layers, and four models were chosen to examine their sensibility when tested against different independent datasets from those used in their original papers. Our studies show that the four models can predict reasonably well under a certain range of vegetation density and submergence, and that the prediction of all the models are less sensitive in the lower region. The studies also reveal that under the same submergence, the predictions of the four models in the upper layer are less sensitive to low vegetation density (e.g. ah <1) than to high vegetation density (ah >1), but that for the same vegetation density, all four models are much sensitive to the vegetation submergence ratio (H/h). It was also found that the Defina and Klopstra models are almost the same despite some simplification made in the Klopstra model, if the same mixing length scale of eddies (A,)is used. Finally, close examination on A, in the analytical models, and it was found that the predictions of the models (the Baptist, Defina and Klopstra models) are less sensitive to the vegetation density and submergence when A, is evaluated by 0.02√Hh.
KW - Analytical model
KW - Open channel flow
KW - Rigid vegetation
KW - Vegetated flow
KW - Vertical velocity profile
UR - http://www.scopus.com/inward/record.url?scp=85056380275&partnerID=8YFLogxK
M3 - Conference Proceeding
AN - SCOPUS:85056380275
T3 - Proceedings - International Association for Hydro-Environment Engineering and Research (IAHR)-Asia Pacific Division (APD) Congress: Multi-Perspective Water for Sustainable Development, IAHR-APD 2018
SP - 567
EP - 576
BT - Proceedings - International Association for Hydro-Environment Engineering and Research (IAHR)-Asia Pacific Division (APD) Congress
A2 - Warniyati, Warniyati
A2 - Legono, Djoko
A2 - Setiawan, Hendy
A2 - Hairani, Ani
A2 - Olii, Muhammad Ramdhan
A2 - Ahmad, Johan Syafri Mahathir
A2 - Karlina, null
A2 - Hambali, Roby
A2 - Benazir, null
PB - Department of Civil and Environmental Engineering, Faculty of Engineering, Universitas Gadjah Mada
T2 - 21st Congress of International Association for Hydro-Environment Engineering and Research-Asia Pacific Division: Multi-Perspective Water for Sustainable Development, IAHR-APD 2018
Y2 - 2 September 2018 through 5 September 2018
ER -