本文應用ROMS模式模擬南灣海域潮流流場，以了解該海域潮流流場特性。本文使用之ROMS原始碼係自公開網域下載取得，實際應用前，先針對影響模式穩定度之因素進行測試，求得最佳之計算時步長與水平渦黏滯係數；再利用實測潮流資料調整模式之底床摩擦係數，以獲得最佳模擬結果。
實際模擬一個月南灣海域潮流流場，結果顯示該海域每日各發生一次順時針及逆時針渦流，順時針渦流規模較逆時針渦流大，可以涵蓋整個南灣海域。在大退潮末期潮流經由貓鼻頭海岬南緣進入灣內，逐漸形成逆時針渦流，該渦流最強發生在小漲潮中期；在大漲潮初期流場呈現順時針渦流分佈，該渦流最強發生在大退潮中期。潮流所產生的平均流，在南灣海域主要呈現順時針渦流，在後壁湖附近另有一小型的逆時針渦流。

ROMS model is applied to understand the characteristic of tidal current in Nan Wan Bay. To get the best setting of time step and horizontal eddy viscosity, the computational stability of the model is carried out first. And then bottom friction coefficient is adjusted by observed data, so as to get the optimal simulation.
The numerical results demonstrate that a counterclockwise eddy and a clockwise eddy exit in the bay everyday, the latter is bigger in size and fills the entire bay. Form lower low water, tidal current passes by the south part of MBT and develops a counterclockwise eddy, until lower high water the current has its maximum. Latter, a clockwise eddy exits in the bay during flood and develop well on the middle of higher high water and lower low water. The tidally-induced averaged current is a clockwise eddy for the most part of the bay and a small size of counterclockwise eddy in the west coast of the bay.

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