2017-01-012024-05-17https://scholars.lib.ntu.edu.tw/handle/123456789/682031摘要：流量資料是防洪工程建設與洪水災害管理的重要依據，由於影響流量的因素非常複雜，傳統的接觸式測量流量方法受限於精度、效率、天氣與人員安全考量已經無法滿足需求，然而非接觸測量受限於表面流場與水下三維流場還未建立明確的關係，因此還無法廣泛應用於現場觀測。如能通過影像以遙測水流表面特性來反推水下三維地形與流場，將可提高非接觸測量流量的時效與精度。水流表面的渦結構常可見于天然河川中，本計畫將以水槽實驗為主，類比不同的同調結構(coherent structure)之演化過程來進行水理研究，在水槽中用高頻PIV 找出表面湍流結構特性、脈動速度、積分尺度與水下湍流渦結構、二次環流間的關係，通過此函數由表面特徵推估水下地形與流場。進一步，以此為基礎，在不同河段與水流條件下用LSPIV 結合無人機實施野外非接觸測量，通過實測資料比較與分析來揭示水面處與水下湍流同調結構之機制與演化過程的相互間複雜關係。本研究的水槽實驗和野外試驗結果可為數值模擬提供基礎性的資料，研究成果更可為將來現場建立大範圍的流量水位監測做好技術上的準備。<br> Abstract: The flow rate data is one of the most important information for the flooding management and disaster control. Our ability to accurately predict the flow rate in open-channel flows using only the free-surface characteristics is currently limited by the capabilities of the measurement instruments and lack of adequate models to describe between the free-surface characteristics, velocity distribution, and bathymetry for the variety of situations encountered in field conditions. This study is concerned with the description of open-channel flow over large-scale roughness and determination of surface coherent structures in view of implementing non-contact, remote discharge estimation techniques. Discharge estimation based on a pointwise velocity measurement at the free surface requires to relate this velocity with the depth-averaged velocity using additional characteristics embedded in the signature of the bed geometry on the free-surface. These problems are addressed through experimental studies. Experiments were performed in a hydraulic flume with varying flow depth and bed roughness. Rectangular ribs and two-dimensional dune-shaped obstacles were placed on the flume bottom to simulate different bed roughness conditions. Time-resolved Particle Image Velocimetry (PIV) measurements were made to obtain coherent structures at various locations. Large-Scale Particle Image Velocimetry (LSPIV) measurements were made to determine the velocity distribution at the free-surface. Combining these data can help to develop the adequate models for discharge measurements with LSPIV. Other than that, the study can provide the constructive information for the numerical modeling and the real-time discharge measurement system.同調結構明渠非接觸測量粒子影像測速Coherent structureOpen channelNon-intrusive measurementLSPIV