本研究主要分為兩個部分，第一部分為整合型座標系統上的應用、第二部分為三相流土石流模擬。本研究將模式皆使用 CUDA 架構進行高效率 GPU 計算，第一部 分採用地形擬合座標系統與傳統卡氏座標系統進行比較兩者在計算上的差異，並且再將地形平滑化的概念，加入地形座標系統中，增加地形座標系統更廣泛的應用於崎嶇地形上的模擬，並以此提出一個整合型地形座標系統，作為土石流災害模擬與沈積物相關的危險流分析。在內文中分別透過理想地形與真實案例應用，探討不同座標系統之間的差異，藉此顯示整合型座標系統的適用性。
第二部分，以地形座標上的二相流數值方法為基礎，建構土石流三相流之理論模型，流體組成包含固體相、懸浮細顆粒相、水相。本研究將其應用於實際案例中，描述崩塌體從山坡滑入河流，濃度較高之土砂碰撞濃度較低流體，兩者不同濃度混合時，對間隙流體的黏滯性產生的巨大變化，土砂將水體往前推移，甚至可能產生湧浪現象，使土石流的模擬能更貼近實際情況。將土石流三相流的模擬結果，與過往研究中使用 CUDA 架構建構之土石流二相流進行結果比較，對照災後衛星影像中比較實際發生路徑，以展現模式應用於現地之可行性。

This paper mainly consists of two parts, the first is the application of an integrated-terrain-following coordinate system, and the second is the three-phase debris flow simulation. The implemented code adopts the CUDA architecture for a GPU-high-efficient computation. The first part compares the discrepancies in results computed in different coordinate systems. Due to the offset caused by the depth integration of the Cartesian coordinate system, and the limitation of shallow curvature of the terrain-fitted coordinate system, this paper proposes an integrated-terrain-following coordinate system. The concept of terrain smoothing is added to the terrain-fitted coordinate system to verify the applicability of the terrain-fitted coordinate system in the simulation of landslide disasters on rough terrain through ideal orographic and practical case applications.
Although the composition of debris flow is complex, the previous research mainly used models of single-phase or two-phase for ease of computation. With these simplified approaches, the significant effects of the clay/silt particle concentration on the viscosity of the debris flow cannot be well described. Accordingly, based on the numerical method of two-phase flow on terrain-fitted coordinates proposed by Tai et al. (2019), the second part is about the construction of a theoretical model of three-phase debris flows, supposed to be composed of the solid, clay/silt particle, and the water phase. The 2009 Hsaiolin event serves as the benchmark application. The interstitial fluid viscosity changed dramatically when the landslide mass approached the river and mixed with the water. The post-event satellite image reveals that there seem to be swells that hit the opposite bank. We compare the simulated flow paths with the bare zones in post-event satellite image. The consistency demonstrates the feasibility of engineering application.

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