Author(s): Kab Keun Kwon; Junwoo Choi; Sung Bum Yoon
Linked Author(s):
Keywords: Equivalent resistance coefficient; Drag interaction coefficient; Unsubmerged rigid multi-piers; Hydraulic experiment; FLOW-3D
Abstract: In order to estimate the equivalent resistance coefficient n-value which represents the total flow resistance including both form drag due to obstructions and bottom friction in open channel flow, the hydraulic experiment was conducted with rigid square unsubmerged multipiers and simulated by using FLOW-3D, a 3-dimensional computational fluid dynamics code. The square multiple piers were arranged with an equal interval along the flow and transverse directions, respectively, and the water depth and the discharge of a mean uniform flow were measured. As applying the experimental and numerical results to the Manning’s equation, the equivalent resistance coefficient n-value was evaluated and the n-values obtained from the experimental and computational results were well agreed. The results showed that the equivalent resistance coefficient varied with the water depth and the intervals between piers. A semi-analytical formula for the equivalent resistance coefficient was derived from momentum analysis including the drag interaction coefficient evaluated based on the experimental results. The drag interaction implicates the influence of flow resistance caused by each of the uniformly arrayed piers on their adjacent piers. The semi-analytical formula agreed with the results of hydraulic experiment and computation. As a result, it was found that when the rigid square unsubmerged obstructions were uniformly arranged in an open channel, the drag interaction coefficient was strongly dependent on the interval between obstructions, and the equivalent resistance coefficient increased with 2/3 power of water depth.
Year: 2010