本研究採用一1.5公尺長，0.1公尺寬，1.0公尺高的矩形玻璃儲槽模型以及氣壓缸的方式迅速抽離擋板讓預先填好的顆粒體模擬出顆粒潰壩(dam-break)實驗，並在於相同初始寬高比(initial aspect ratio)下，使用顆粒粒徑比的不同及改變細粉含量大小下探討顆粒崩塌流流動性及運動狀態之影響。且為了捕捉到顆粒崩塌瞬間每一個時間點運動變化，透過高速攝影機以及搭配PIV技術(Particle image velocimetry)來觀察顆粒崩塌流速度上的變化以及特定時間點下其速度剖面的差異。
由實驗結果得知隨著細粉含量的增加，使得細粉存在於粗顆粒中因崩塌過程重力驅動使得崩塌狀態下細粉的旋轉減少了粗顆粒及壁面之間摩擦而造成的潤滑效果(lubrication effect)，造成其整體崩塌持續時間增長，流動性因此而變得較佳。且顆粒崩塌流動過程，因細粉滲透與粗顆粒分離而造成粗顆粒浮出在崩塌自由表面上，而造成粗顆粒在細粉所形成的潤滑層上流動來增加其流動性。且藉由分析特定位置(δL/3+Li)下顆粒流動的速度剖面來探討顆粒崩塌深度上速度至自由表面上的速度變化，以及隨著細粉含量的增加所造成顆粒崩塌流其流動性的增加。

In this study, we used a pneumatic cylinder to quickly lift the baffle through air intake and exhaust, so that the pre-filled particles collapsed instantaneously to conduct a series of particle collapse experiments. And under the same initial aspect ratio, use different particle size ratios and change the content of fine particles to observe the difference in particle flow behavior. In order to capture the changes in particle motion when the particles collapse, high-speed cameras and PIV technology (particle image velocimetry) are used to observe the changes in the flow velocity of the particle collapse and the velocity distribution at a specific characteristic time point of the particle collapse.
According to the experimental results, as the content of fine particles increases, the rotation of the fine particles in the collapsed state of the fine particles between the coarse particles will reduce the lubrication effect caused by the friction between the coarse particles and the wall surface, and cause its overall duration to increase collapse mobility. Due to the infiltration of fine particles and the separation of coarse particles, the process of particle collapse and flow produces a pure particle layer on the collapsed free surface. By analyzing the velocity distribution of the particle flow at a specific location (δL/3+Li), the velocity in the depth direction can be analyzed. The effect of surface velocity changes and particle collapse flow caused by the increase of fine particles.

[1]Rondon, L., Pouliquen, O., and Aussillous, P., “Granular collapsein a fluid: Role of the initial volume fraction,” Physics of Fluids, 23, 073301, 2011.
[2]Lube, G., Huppert, H. E., Sparks, R. S. J.,and Freundt, A., “Collapses of two-dimensional granular columns,” Physical Review E, 72, 041301, 2005.
[3]Lajeunesse, E., Monnier, J. B., and Homsy, G. M., “Granular slumping on a horizontal surface,” Physics of Fluids, 17, 103302, 2005.
[4]H . T . Chou and C. F Lee., “Falling process of a rectangular granular step,” Granular Matter, 13:39–51, 2011.
[5]Lube, G., Huppert, H. E., Sparks, R. S. J., and Freundt, A., “Static and flowing regions in granular collapses down channels,” Physics of Fluids, 19, 043301, 2007.
[6]Artoni, R., Santomaso, A. C., Gabrieli, F., Tono, D., and Cola, S., “Collapse of quasi-two-dimensional wet granular columns,”Physical ReviewE, 87, 032205, 2013.
[7]Gongdan, Z., Wright, N. G., Qicheng, S., and Qipeng, C., “Experimental Study on the Mobility of Channelized Granular Mass Flow,” Acta Geologica Sinica, Vol.90, pp.988-998, 2016.
[8]Dade,W.B., and Huppert, H. E., “Long-runout rockfalls,”Geology.,Vol26, pp.803-806, 1998.
[9]Zhou, W., Xu, K., Ma, G., Yang, L., and Chang, X., “Effects of particle size ratio on the macro- and microscopic behaviors of binary mixtures at the maximum packing efficiency state,” Granular Matter, 18:81, 2016.
[10]Meruane, C., Tamburrino, A., and Roche, O., “Dynamics of dense granular flows of small-and-large-grain mixtures in an ambient fluid,” Physical Review E, 86, 026311, 2012.
[11]Linares-Guerrero, E., Goujon, C., and Zenit, R., “Increased mobility of bidisperse granular avalanches,” J. Fluid Mech, vol.593, pp.475-504, 2007.
[12]Vallejo, Luis E., Espitia, Jairo M. and Bernardo Caicedo., “The influence of the fractal particle size distribution on the mobility of dry granular materials,” EPJ Web of Conferences, 140, 03032, 2017.
[13]Phillips, J., Hogg, A., Kerswell, R., and Thomas, N., “Enhanced mobility of granular mixtures of fine and coarse particles,” Earth and Planetary Science Letters, 246, pp.466-480, 2006.
[14]Adrian, Ronald J., “Image shifting technique to resolve directional ambiguity in double pulsed velocimetry,” Applied Optics, Vol. 25, pp.3855-3858, 1986.
[15]Du Pont, S.C., Fischer, R., Gondret, P., Perrin, B., Rabaud, M., “Wall effects on granular heap stability,” Europhys. Lett., 61(4), pp.492–498, 2003.
[16]Liao, C. C., Ou, S. F., Chen, S. L., and Chen, Y. R., “Influences of fine powder on dynamic properties and density segregation in a rotating drum,” Advanced Powder Technology, vol.31, pp.1702-1707 ,2020.
[17]Huang, X., Bec, S., and Colombani, J., “Ambivalent role of fine particles on the stability of a humid granular pile in a rotating drum,” Powder Technology, 279, pp.254-261, 2015.
[18]Huang, X., Bec, S., and Colombani, J., “Influence of fine particles on the stability of a humid granular pile,” Physical Review E, 90, 052201, 2014.
[19]Lube, G., Huppert, H. E., Sparks, R. S. J., and Hallworth, M. A., “Axisymmetric collapses of granular columns,” Journal of Fluid Mechanics, 508, pp.175–199, 2004.
[20]Lajeunesse, E., Mangeney-Castelnau, A., and Vilotte, J. P., “Spreading of a granular mass on a horizontal plane,” Physics of Fluids, 16(7), pp.2371–2381, 2004.
[21]Xu, X., Sun, Q., Jin, F., and Chen, Y., “Measurements of velocity and pressure of a collapsing granular pile,” Powder Technology, 303, pp.147–155, 2016.
[22]Girolami, L., Hergault, V., Vinay, G., and Wachs, A., “A three-dimensional discrete-grain model for the simulation of dam-break rectangular collapses: comparison between numerical results and experiments,” Granular Matter, 14(3), pp.381–392, 2012.
[23]Bonamy, D., Daviaud, F., and Laurent, L., “Experimental study of granular surface flows via a fast camera: A continuous description,” Physics of Fluids, 14(5), pp.1666–1673, 2002.
[24]Torres-Serra, J., Romero, E., and Rodríguez-Ferran, A., “A new column collapse apparatus for the characterisation of the flowability of granular materials,” Powder Technology, 2019.