| 摘要: | 本研究探討了不同飽和狀態下兩相局部潰壩流場中顆粒流動的行為，並對顆粒流動及沉積現象進行詳細分析。實驗使用一個長120 cm、寬10 cm、高50 cm的類二維水平流槽，填充預先準備好的顆粒柱，在相同的初始縱橫比(initial aspect ratio)下，透過氣壓缸快速抽離擋板，以模擬顆粒崩塌(dam-break)現象。實驗中，使用高速攝影機拍攝顆粒崩塌的動態過程，並進行影像處理分析。此外，採用粒子影像測速法(Particle image velocimetry, PIV)來計算顆粒流動時的速度場分布。實驗結果通過分析顆粒及間隙流體在不同特徵時間下的輪廓圖，研究顆粒的跳動距離和下降距離，計算顆粒前沿速率及下降速率，並探討其崩塌的持續時間。此外，通過開源軟體PIVlab分析每個特徵時間點的速度場分布，求得流動層面積，以了解顆粒流動行為在不同飽和度、間隙流體黏滯度及閘門開度條件下的變化。
由實驗結果得知，在不同液體飽和度、間隙流體黏滯度及閘門開度對兩相流顆粒崩塌的流動行為產生顯著影響。隨著液體飽和度的增加，顆粒跳動距離、下降高度及速率均顯著提升，這表明液體在顆粒間降低了內聚力，促進了顆粒的流動和擴散。閘門開度的增加，導致更多顆粒和液體混合物通過閘門，使得跳動距離增加，而下降高度和速率則呈現先上升後下降的趨勢，崩塌持續時間隨之縮短。隨著間隙流體黏滯度的增加，跳動距離相對減少，但在過飽和狀態時相差不大，主要是因為液體位能的影響較大導致黏滯度對跳動距離的影響減弱，而下降高度和速率在未飽和及過飽和狀態下均隨黏滯度增加而下降。在飽和狀態下，發現一個特別的情況，其甘油水溶液的下降速率較慢，但其下降的高度比水還要來的大，這是由於高黏滯度流體對顆粒運動的影響，使顆粒在較長時間內保持運動狀態，從而增加最終的下降高度，然而，由於流體阻力較大，使得顆粒初始運動速率相對較低。最後，我們從速度場剖面發現不同實驗組之間存在顯著的流動行為差異，包括速度大小和速度向量的變化。通過這些數據的分析，我們進行了流動層面積的比較，以比較各組實驗中顆粒和間隙流體的動態行為。
;This study investigates the behavior of particle flow in a two-phase localized dam-break flow under different saturation conditions, with a detailed analysis of particle flow and deposition phenomena. The experiments were conducted using a quasi-two-dimensional horizontal flume, measuring 120 cm in length, 10 cm in width, and 50 cm in height. Prepared particle columns with the same initial aspect ratio were used, and the baffle was quickly removed using an air cylinder to simulate a dam-break scenario. High-speed cameras captured the dynamic process of particle collapse, and image processing analysis was performed. Additionally, Particle Image Velocimetry (PIV) was employed to calculate the velocity field distribution during particle flow. The experimental results were analyzed by examining the profiles of particles and interstitial fluid at different characteristic times, studying the particle runout distance and descent distance, calculating the front velocity and descent velocity of particles, and investigating the collapse duration. Furthermore, the open-source software PIVlab was used to analyze the velocity field distribution at each characteristic time to determine the area of the flowing layer, thereby understanding the variations in particle flow behavior under different saturation levels, interstitial fluid viscosities, and gate openings.
The experimental results indicate that different liquid saturation levels, interstitial fluid viscosities, and gate openings significantly impact the flow behavior of two-phase particle collapse. As liquid saturation increases, particle runout distance, descent height, and velocity all show significant improvement, indicating that the presence of liquid reduces cohesion between particles, promoting their flow and dispersion. An increase in gate opening leads to more particles and liquid mixture passing through the gate, resulting in an increase in runout distance, while descent height and velocity initially increase and then decrease, and the collapse duration is shortened accordingly. With increasing interstitial fluid viscosity, runout distance decreases relatively, but the difference is not significant under supersaturated conditions due to the greater influence of liquid potential energy, which weakens the impact of viscosity on runout distance. Descent height and velocity decrease with increasing viscosity in both unsaturated and supersaturated states. In the saturated state, a special situation is observed where the descent velocity of the glycerol-water solution is slower, but its descent height is greater than that of water. This is because high-viscosity fluid affects particle motion, allowing particles to remain in motion for a longer time, thereby increasing the final descent height, while the initial particle motion velocity is relatively lower due to greater fluid resistance. Finally, from the velocity field profiles, significant differences in flow behavior among different experimental groups were observed, including variations in velocity magnitude and velocity vectors. These data analyses allowed for a comparison of the flowing layer areas to quantify the dynamic behavior of particles and interstitial fluids in each experimental group. |
