高密度射流入寬水庫之實驗量測分析平面映射密度場與表面速度場之研究

Experimental Density and Surface Velocity Mapping of Dense Jets Plunging into a Wide Reservoir

伍亭竹(Ting-Chu Wu)

指導教授 ： 卡艾瑋

國立臺灣大學/工學院/土木工程學研究所/碩士(2021年)

https://doi.org/10.6342/NTU202102019

摘要

本論文主要研究目標為平面座標中異重射流流入寬渠道的行為。實驗渠道採用透明壓克力作為材料，鹽水作為高密度流體，從穩定的窄入流裝置流入注滿水的寬渠道，進行一系列的水工模型試驗。此研究主要分為兩大實驗部分，一方面為密度分布場實驗分析，另一方面為表面速度場實驗分析。
密度分布場的實驗是以亞甲基藍作為染劑，光線從渠道下向上照射，利用比爾朗伯的光吸收基本定律，由亮度判定各位置的濃度，藉此得到密度場。而在表面速度場方面則是使用螢光顆粒，紫光燈由上往下照射，以數位攝影機觀察大範圍表面速度變化，與高速攝影機觀察的局部表面速度變化做疊合，使用顆粒追蹤的方式分析流速。最後將不同實驗條件下之分析結果進行比較。
結果顯示，入射流的密度越高，表面流速會下降，而隨著入射流的密度變高，密度深度也會大致上隨之降低。除此之外，我們還可以從速度場隨時間的變化觀察其擺盪以及渦漩的現象。

關鍵字

高密度射流 ； 平面座標 ； 密度率定 ； 密度分布場 ； 表面速度場 ； 顆粒追蹤法

並列摘要

In this thesis, the main research goal is to study the dense jets plunging into a wide channel by a series of small-scale laboratory experiments. In the experiments, the channel is made of transparent acrylic, and salt water is used to simulate the high-density fluid. The constant dense jet flows into a wide channel filled with water. The research is mainly divided into two experimental parts, one part is density fields experiments, and the other one is velocity fields experiments.
The part of density fields experiments is used Methyl Blue dye to indicate density flow. We light up the channel from the bottom, getting the luminance in each position. After using Beer–Lambert law to analyze the concentration in each position, we can get the density fields. The part of surface velocity fields experiments is added fluorescent particles on the water surface and lighting from the top by black, recorded the experiments by digital camera and high-speed camera simultaneously. The digital camera is used to capture a wide range, while the high-speed camera is focusing on the section near the inflow. Overlapping these two parts to get the surface velocity fields by particle tracking velocimetry. Finally, compare the analysis results under different experimental conditions.
The results show that the surface velocity decreases with the increasing concentration of inflow; the density thickness roughly decreases with the increasing concentration of inflow. In addition, we can also observe the changes of the velocity fields over time, observing their swinging phenomenon and the vortexes.

並列關鍵字

dense jets ； mapping ； concentration calibration ； density fields ； surface velocity fields ； particle tracking velocimetry

參考文獻

Ahmed, D. I., Latrache, N., Nsom, B. (2015). Applied the large scale particle image velocimetry technique for measurement the velocity of gravity currents in the laboratory. Journal of Water Resource and Protection, 7(08), 597.

Capart, H., Young, D. L., Zech, Y. (2002). Voronoï imaging methods for the measurement of granular flows. Experiments in Fluids, 32(1), 121-135.

Cui, P., Zeng, C., Lei, Y. (2015). Experimental analysis on the impact force of viscous debris flow. Earth Surface Processes and Landforms, 40(12), 1644-1655.

Huang, M. Y. F., Huang, A. Y. L., Capart, H. (2010). Joint mapping of bed elevation and flow depth in microscale morphodynamics experiments. Experiments in Fluids, 49(5), 1121-1134.

Lai, C. C. K., Lee, J. H. W. (2012). Mixing of inclined dense jets in stationary ambient. Journal of Hydro-environment Research, 6(1), 9-28.