初始體積占有率影響顆粒崩塌行為之研究;The Effect of Initial Volume Fraction on Granular Collapse

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题名:	初始體積占有率影響顆粒崩塌行為之研究;The Effect of Initial Volume Fraction on Granular Collapse
作者:	林奕均;Lin, Yi-Chun
贡献者:	能源工程研究所
关键词:	顆粒流;體積占有率;潰壩;granular flow;volume fraction;dam-break
日期:	2017-12-18
上传时间:	2018-01-16 10:44:42 (UTC+8)
出版者:	國立中央大學
摘要:	本研究在一矩形玻璃槽中進行乾顆粒崩塌實驗，控制崩塌前顆粒床體的體積佔有率，分析並探討其崩塌流態及流場速度結果。實驗設備為一長70公分長，10公分寬矩形槽體，及能迅速抽離槽體以模擬潰壩崩塌之壓克力檔板。研究中針對0.60、0.62、0.64、0.65四組體積佔有率及粗細兩種顆粒試體的實驗設置拍攝實驗影像，分析其隨時間變化的輪廓剖面、破壞面、沉積速度及角度。並以PIV (Particle image velocimetry)技術計算顆粒崩塌流的速度。實驗結果顯示，細顆粒顆粒體積較小，達到相同體積占有率時等重的顆粒數較粗顆粒更多，顆粒的接觸點多摩擦力大，因此顆粒體較粗顆粒更能維持結構。而各組實驗在體積占有率上升的同時，顆粒間的間隙被更多的小顆粒填充，結構的穩定性提升，崩塌延遲、流動層縮小。但崩塌的速度值是與顆粒堆積的高度關係較大，雖然因體積佔有率的上升而略有下降，但崩塌過程速度的極值出現在自由表面，在同樣寬高比的各組實驗下速度極值及速度變化的進程相近。;This study experimentally investigates the dam-break collapse process of a dry granular step in a transparent glass chute by particle image analysis. Two types of uniform spherical glass beads were piled up with four different bed volume fraction to elucidate their flow characteristics. For all cases in this study, the pile bed high and aspect ratio are all the same. PIV (Particle image velocimetry) were used to analysis for the velocity profiles measured at the side wall. Failure surface, deposit profile and flow regime are discussed by processing the recorded image. The case with fine particles shows more stability than coarse case during the experiment because there are more particles contacted which bring about higher friction angle. The effect of increasing volume fraction is similar, like the flow area of collapsing of dense cases are smaller than loose one. But there is not much effect of volume fraction on velocity magnitude. The variety of velocity in the process and the maximum value in each cases are approximative.
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