報告書番号

U03001

タイトル（和文）

粒子を伴う流れによる付着藻類の剥離特性

タイトル（英文）

Experimental and Numerical Study for Effects of Contact Solids on Algal Detachment

概要 （図表や脚注は「報告書全文」に掲載しております）

本研究では，土砂移動を伴う流れの付着藻類剥離特性に関する基礎的な知見の把握と予測手法の開発のため，室内実験水路を用いた付着藻類の剥離実験とその数値シミュレーションを実施した．実験では水路内に藻類を付着させたブロックを設置し，流水中に球形粒子や川砂利を投入することにより，粒子接触による藻類の剥離効果を評価した．また，数値シミュレーションでは，粒子接触による藻類剥離モデルを構築し，離散要素法を基にした３次元粒子移動モデルへ取り込みを行った．開発した数値シミュレーション手法の検証のため，実験の再現解析を実施した結果，開発した数値シミュレーション手法を用いて，実験における粒子移動速度や付着藻類残存率の変化特性を比較的良く模擬できることを確認した．

概要 （英文）

In this study, an experiment was conducted in a laboratory to evaluate effects of bed load on the detachment of algae on riverbed. In the experiment, an algae-covered block was placed in the testing flow channel and a certain amount of spherical particles or gravel were continued to add into the flow for an hour. Accordingly, the algae were gradually detached from the block by contact of particles which were transported by flowing water. It was found through the experiment that detachment of algae was increased under conditions of higher particle concentration, larger diameter of particle and faster current.Moreover, a numerical model for evaluating algal detachment due to contact of solid particles was developed. The model was constructed on the basis of a discrete element method, which could compute each solid particle motion in the flow independently, and was applied to simulate the experimental results in the laboratory flow. As a result, it was shown that the predicted velocity profiles of particles and the algal detachment rate due to the particles agreed well with the experimental results.

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