水下爆炸現象與附近不同厚度嵌板結構交互影響的模擬研究

THE SIMULATION STUDY OF THE INTERACTION BETWEEN UNDERWATER EXPLOSION PHENOMENON AND NEARBY CLAMP PLATE STRUCTURE

水下爆炸有震波與氣泡兩種現象，震波的影響研究較常見，氣泡的研究多在空化領域。水下爆炸氣泡因為複雜且試驗資源需求高，以致文獻較少。但是氣泡的影響不容小覷，氣泡產生的影響與震波疊加，可能產生震波階段無法發生的破壞，因此有必要將震波與氣泡影響綜合討論。作者模擬嵌板附近的水下爆炸，探討震波、氣泡與嵌板的交互影響。嵌板幾何形狀簡單，容易製作數值模型，容易與理論比對，適宜由此開始建立研究基礎。作者使用FEM軟體LS-DYNA，運用其ALE及FSI計算法模擬不同間距、不同厚度嵌板受水下爆炸影響的反應。比較理論、試驗結果，確認板中心速度、應變、氣泡漲縮、噴流、崩潰等行為，模擬均與之相符，驗證模擬方式正確。根據模擬結果發現震波、氣泡漲縮與結構振動模式是交互影響的，結構振動在彈回時推擠氣泡，改變氣泡收縮到崩潰的形狀，從而變化噴流形狀尖端速率及脈衝特性，其脈絡關係複雜，值得進一步研究。這些觀察是試驗難以做到的，說明模擬的價值。後續將由這個基礎精進，試圖釐清複雜的交互作用現象及進行較接近真實場景的應用。

Underwater explosion (UNDEX) has two phenomena: shock wave and bubble. Papers subject to shock wave are more common than bubble. UNDEX bubble is much complex and higher level of experiment resource requirements than shock wave, papers of UNDEX bubble are rare, and most of the related papers are in the field of cavitation. However, the power of bubble should not be underestimated, influences by bubble can superimpose with the influences of shock wave, and result damage that shock wave can’t produce alone, so it is necessary to discuss shock wave and bubble at same time. The author simulated an UNDEX near a clamped plate structure; explore the interaction between shock wave, bubble and clamped plate. Clamped plate has simple geometry, easy to build numerical model and easy to compare with theories, is an appropriate point to start the exploration. The author uses FEM software LS-DYNA and its ALE, FSI algorithms to simulate UNDEX phenomenon near clamp plates with different thickness and stand-off. By comparing with theories and experiment results, showing the behavior of plate center velocity, strain, bubble expansion and contraction, jetting and collapse, are all match. Verify that the simulation methods are correct. From the results of simulation, the interactions between shock wave, bubble and structural are discussed. When plate vibration is excited by shock wave, its rebound can be hindered by following bubble expansion, and this delated rebound will in turn influence the characteristics of bubble collapse, bubble shape, pulsation and jet. The contexts or relations inside are complex, worth further investigation. These observations are difficult to conduct experimentally, illustrate the value of simulation. In future, the author will attempt to clarify complex interaction phenomena and make applications to real scenarios base on this foundation.