穩態乾顆粒流經障礙物之作用力: 即時量測與藉影像分析之估測

In-Situ and Image-Based Force Measurement for a Steady Dry Granular Flow Over an Obstacle

江明哲(Ming-Jhe Jiang)

指導教授 ： 楊馥菱

國立臺灣大學/工學院/機械工程學研究所/碩士(2012年)

https://doi.org/10.6342/NTU.2012.03050

摘要

本實驗探討流經傾斜滑道的穩態乾顆粒流，並以兩顆荷重元與一張力感測器組成長方形障礙物，以即時量測顆粒流跨越障礙物時所產生的衝擊力，荷重力， 與側向摩擦力。同時輔以高速照相機由滑道側邊拍攝顆粒流之行為，配合影像分析求得顆粒流之速度與密度，進一步以體積控制分析(control volume analysis)計算顆粒流所產生的力並與即時量測之衝擊力，荷重力，與側向摩擦力比較。體積控制分析與即時量測的結果吻合，同時在比較的過程之中發現質點軌跡測速法(PTV)無法作用於顆粒流過於稀疏的情況。
在產生穩態顆粒流的過程，發現儲存槽內不同的堆積幾何形狀會影響出口的顆粒排放速度，當堆積的長度小於某一特定長度時，流出的顆粒總量與時間的關係會呈現出不同的趨勢。為解釋此現象，我們以高速影像探討其可能原因。

關鍵字

穩態乾顆粒流 ； 即時量測 ； 質點軌跡測速法

並列摘要

This work attempts direct and indirect measurements for the force developed by a steady dry granular flow down an incline as it impinges and runs over an obstacle constructed by putting together two load cells and one shear cell. Three load cells were implemented to achieve in-situ measurements of the impact force, the tangential friction, and the overhead normal loads. High-speed imaging technique and relevant image analysis were employed to estimate depth profiles of the flow density and velocity which information were further integrated into a two-dimensional control
volume analysis to estimate the corresponding force components using the requirement of streamwise momentum conservation. The force data obtained from the
3D in-situ and 2D indirect measurements agree well over the inspected inclination angles, 23 and 26 degrees, provided that the flow is not too loose or too thin for which
erroneous PTV is inevitable. In addition, we also discover unique temporal profiles for reservoir discharge and explanations are given based on relevant high-speed
imaging analysis.

並列關鍵字

steady dry granular flow ； in-situ measurements ； Particle Tracking Velocimetry

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