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Change in Flow Structures Inside an Armor Layer by the Layer Thickness and the Existence of Periphyton Mat

Author(s): Norio Tanaka; Yu Hasemi

Linked Author(s): Norio Tanaka

Keywords: No Keywords

Abstract: Flume experiments were conducted for clarifying the turbulent structure and shear stress characteristics in the armored stone-bed layer with and without periphyton mat on the gravels. The periphyton model (PEM) was set as a cross-stream roughness element on the stone considering the similar additional drag and lift characteristics. Flume experiments were conducted, flow structure was visualized and flow field was measured using a Particle Image Velocimetry. Effects of submergence of the large stones were investigated through the vertical distribution of velocity and Reynolds stress. Momentum exchange between the upper layer and the armor layer occurred through the eddies generated behind the roughness elements in case without PEM, however the momentum exchange was reduced, and the location of maximum Reynolds stress was shifted up. The three dimensional turbulent structure around the stone is changed and the flow becomes a skimming type flow, by the existence of the PEM.

DOI:

Year: 2018

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