流體對滾動圓桶中二相顆粒流之影響

Abstract

本文研究顆粒於滾動圓桶中在不同間隙流體及不同轉速下之穩態運動行為。實驗過程使用高速攝影機搭配影像處理以及粒子追蹤測速法(Particle Tracking Velocimetry, PTV)計算出顆粒的瞬時速度，透過空間平均進而求出各種不同的流場性質及重要參數。包括體積分率、混合體平均速度、流動層厚度、應變率、顆粒溫度，觀察分析出間隙流體對於顆粒行為之影響。發現混合體之性質在乾、濕及完全沉浸狀況與在半沉浸及甘油沉浸狀況下有明顯的不同。 此外再由觀測混合體於自由表面的主流速度與滾筒轉速之關係配合Tegez等人在2003年發表的學術文章，將混合體流動行為分類為顆粒流(Granular flow)、暫態流(Transition flow)及黏塑性流(Viscoplastic flow)三種類型。

This article studies the steady state particle motion in a rotating drum with various interstitial liquids and at different drum speeds. An image analysis routine, that integrates Circular Hough Transformation and particle tracking velocimetry, has been developed to monitor the instantaneous individual particle velocity. Through a spatial and temporal average scheme, the bulk quasi-steady behavior was obtained which consider the collective particle motions as a continuum. The flow properties were investigated, including the solid-volume concentration, bulk velocity components, flowing layer thickness, bulk normal and shear strain rates, and granular temperature. Special efforts were made to investigate the influences of interstitial liquid on these granular flow dynamic properties. It is observed that the flow behaviors of the dry, water-wetted, and water-submerged cases are much different to the water-saturated and glycerol-saturated cases. A comparison between the flow surface velocity and the drum speed was made following the work by Tegez et. al. (2002[6], 2003[7]). Possible flow classifications – a granular, a transitional, or a viscoplastic type – is attempted according to the current experimental findings.