Experimental study on large wood filtration performance by herringbone water-sediment separation structure

A herringbone water-sediment separation structure (hereinafter referred to as "herringbone structure") has been shown to be effective in separating coarse inorganic debris; however, less is known regarding the large wood (LW) filtration effect in this structure. This paper presents preliminary research on the wood filtration effect of the herringbone structure based on physical model tests. The results show that the herringbone structure exhibited effective performance in large wood size segregation, with a 100% component filtration rate for LW that diameter (D) larger than ribbed beam opening width (a). The total filtration rate also exceeded 80% when the Fraud number (Fr) is larger than 2.64 and increased with the increase of Fr. After exceeding Fr_max, total filtration rate would be decreased due to overflow. Beside flow condition, structure parameters influence significantly on LW filtration rate. We attempt to explain the filtration process via particle contact trajectory and particle movement trajectory. The inclined angle of ribbed beam (γ) contributed the most variation to the filtration rate via influencing the coincidence with particle contact trajectory and particle movement trajectory. The high sensitivity coefficient of ribbed beam (θ) under relatively low Fr conditions implies remarkable influences on LW filtration effects by causing clogging problem. The ribbed beam opening width (a) together with LW diameter (D) influenced the size segregation performance.