以實驗方法研究孤立波於黏性泥床上過垂直圓柱

Abstract

孤立波是一種波浪形式，其非線性和頻散效應之間的平衡特性使其能夠長時間保持完整性。然而，對於孤立波作用於黏性泥床上的速度場研究仍然有限，尤其是針對孤立波作用於黏性泥床上的垂直圓柱結構物周圍的速度場的研究更加缺乏。以往的文獻主要使用真實的泥土進行實驗，但是由於泥土不透光，無法通過光學方法獲取高精度和高空間解析度的速度場測量數據。在本研究中，以透明黏性流體模仿泥土，並利用粒子影像測速法（particle image velocimetry, PIV）測量了孤立波傳遞到黏性泥床中的垂直圓柱結構物周圍的速度場，同時，利用Canny 邊緣偵測方法捕捉了泥面起伏的變化情況。研究結果顯示，黏性泥床會產生回流現象，即向波浪傳播的反方向流動。當孤立波通過垂直圓柱結構物時，我們觀察到在結構物的迎流側，泥面先上升再下降，而在背流側，泥面也呈現類似的變化。這項研究對於孤立波、黏性泥床和垂直圓柱結構物之間的相互作用，與實驗室前人研究的定性比較結果相似，並提供了較新穎的實驗方法，同時也提供了實驗數據供數值模型進行比對。

Solitary waves are a wave phenomenon that maintains integrity over a long duration due to the balance between nonlinearity and dispersion effects. However, there is limited research on the velocity field of solitary waves acting on a viscous mud bed, particularly around vertical cylindrical structures. Previous studies mainly employed real soil in experiments, but the opaqueness of soil restricts the acquisition of high-precision and high-spatial-resolution velocity field measurements using optical methods. In this study, a transparent viscous fluid was used as a surrogate for soil, and Particle Image Velocimetry (PIV) was employed to measure the velocity field around vertical cylindrical structures as solitary waves propagated into the viscous mud bed. Additionally, variations in the mud surface were captured using the Canny edge detection method. The results revealed the occurrence of flow reversal, i.e., flow in the opposite direction of wave propagation, in the presence of the viscous mud bed. As the solitary wave passed the vertical cylindrical structures, we observed an upward and then downward movement of the mud surface on the upstream side, while a similar pattern was observed on the downstream side. This study provides insights into the interaction between solitary waves, viscous mud beds, and vertical cylindrical structures, validating qualitatively with previous laboratory studies and offering a novel experimental approach and data for numerical model comparisons.