當波浪通過波狀底床時，特定頻率之波浪會與底床有顯著的交互作用現象， 進而產生強反射，此現象稱作布拉格共振(Bragg resonance)，而前人研究中提 出受到均勻順向流作用下，共振發生頻率會改變，本文以開源計算流體力學軟 體OpenFOAM進行模擬，希望能以數值分析的方式，模擬受順向、逆向均勻 流作用下之布拉格共振現象，並瞭解局佈流場之特性。
本模式求解雷諾平均N-S方程式，以有限體積法進行偏微分方程式之離散， 並以流體體積法(VOF)追蹤自由液面變化，為合理模擬入、反射波受流作用為 相反，模式選擇造波方法為內質源造波法(Internal mass source wavemaker)，配 合數值海綿層消波(Numerical sponge layer)，造流方法則以鬆弛法(Relaxation method)概念造流，這些數值方法不僅成功模擬波浪與順、逆向均勻流交互作 用，且無須為了避免反射問題將水槽拉長，進行長時間模擬，另外為了分析有 流作用下之反射率，本研究重新推導計算反射率法－三點法並考慮流的影響。
純波、純流、波流交互作用之數值結果與Tsao(1959)之解析解比較，波高 的模擬於波流交互作用時略有不符，故以調整已知波高來造出預期之波浪，而 波長的模擬則與理論預測相當符合。
本研究應用使用之水槽設計參考Magne等人(2005)之實驗水槽設計，於波 狀底床前後考慮存在緩衝斜坡段，數值計算結果趨勢與實驗資料相符合，且能 夠以理論共振發生條件預測主要、次要共振發生之條件，並進一步分析波狀底 床附近之速度場、渦度場。

Present study aims to simulate Bragg resonance phenomenon in the presence of uniform
currents with OpenFOAM CFD tools. Water waves interact with both following and
opposing currents passing through sinusoidal bottom with ramps.
Incident waves are generated by internal mass source method, and sponge layers located at
two sides of flume, which are used for dissipating the outgoing waves and maintaining a
uniform current simultaneously. Theoretically, wave number will change due to the
existence of current. In order to estimate reflectivity, present study modifies the three-point
method considering different wave number between incident and reflected wave.
Numerical model in the study solves the Reynolds Averaged Navier-Stokes (RANS)
equations with k-eplison turbulence closure scheme, and free surface deformation is tracked
by volume of fluid method (VOF).
The numerical model simulation capability in wave-current interaction is validated by
theoretical solution and results are in good agreements. After that, wave, current and
sinusoidal bottom interaction are simulated with different current strength and direction.
Results of the case with no current are compared with experiment data and find resonance
occurring conditions of main and secondary resonance. The conditions successfully predict
resonance occurrence both in following and opposing current conditions. Besides, when
current passes through sinusoidal bottom, there is obvious vortex occurring because of
separation phenomenon.
Present study realizes wave and current interaction in OpenFOAM, especially opposing
current condition, and applies to Bragg resonance simulation. Numerical results extend the
theory resonance condition deriving from potential flow model, which find secondary
resonance condition and successfully predict resonance occurrence under uniform current
even if obvious vortex occurs near the bottom.

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