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3D Numerical Experiments on Drag Resistance in Vegetated Flows

Author(s): Dimitris Souliotis; Panagiotis Prinos

Linked Author(s): Panagiotis Prinos

Keywords: Drag resistance; Submerged vegetation; Drag coefficient; RANS

Abstract: In this work three dimensional computations, based on the RANS equations and a turbulence model of the k-ε type, have been performed for calculating drag resistance in a vegetated channel for various submergence ratios and vegetation densities. The submergence ratio, H/h (H=flow depth, h=vegetation height) varies from 1. 17 to 5. 0 and the vegetation density α (α= A/V, A= frontal area of the cylinder and V= volume influenced by a single cylinder) from 2. 048 to 4. 3. The vegetation is considered three-dimensional, rigid, simulated as cylindrical roughness and arranged in a staggered or a non-staggered pattern according to experimental data (Garcia and Lopez, 2001, Poggi et al., 2004 and Huthoff et al., 2006). Four methods have been used for the calculation of the drag coefficient, Cd: (a) direct calculation from the computed distribution of the respective forces and (b) three indirect methods based on the simplified momentum equation (by including and excluding the gradients of the significant shear stress) and on the force balance between gravity force and drag force. The effect of submergence ratio (H/h), Reynolds number (Re) and array density (αdr) on Cd is investigated.


Year: 2007

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