現今五代戰機的內置彈艙，在高巡航速度飛行下，會因自由剪切層的撞擊，在彈艙內部形成封閉流場系統，使得彈艙內產生較大的壓力梯度以及高分貝數的噪音，這會導致戰機在極度危險的條件下飛行。因此本研究運用低成本CFD(Computational Fluid Dynamics)計算流體技術，模擬殲-31在穿音速和超音速流場條件下，裝載一、二、四顆飛彈後，內部封閉流場系統所造成OASPL(Overall Sound Pressure Level)總聲壓級和壓力梯度的改變，以及內部可能產生共振之頻率峰值，提前幫助彈艙設計者預測可能發生的危害。使用DES(Detached Eddy Simulation)分離渦流模擬搭配SST k-ω紊流模型，進行殲-31彈艙內的氣動特性模擬，主要使用非結構六面體網格進行節點的劃分，而為了增加本研究計算之可信度，首先與美國阿諾德工程發展中心的風洞實驗，進行彈艙內的聲場與流場數據之比較驗證，驗證結果表明:數值方法可以在相對誤差2%內，準確預測頻率峰值的產生，而彈艙內的壓力係數分布預測，也是與實驗相當吻合。本研究在網格獨立性結果發現，較精細的網格可以解析出較準確的壓力波傳遞訊號，而這會使得壓力訊號在經過快速傅立葉後，高頻率的頻率峰值將會被解析出來，本研究也從模擬結果推測若再進一步增加網格，將可以解析出更高頻率的峰值。
本研究在殲-31彈艙模擬結果表明:飛彈的裝載會使內部流場更加複雜，使得內部壓力梯度增加，以及更容易受到攻角的改變，而產生較劇烈的擾動，但OASPL總聲壓級數據結果顯示，飛彈裝載不會使得噪音分貝數的上升，而值得注意的是，彈艙前緣與後緣的鋸齒狀幾何，會改變彈艙內最大分貝數的分布，這也明確說明幾何外型所改變自由剪切的流動，會導致完全不同的聲場分布。

This study uses low-cost CFD (Computational Fluid Dynamics) to simulate the OASPL (Overall Sound Pressure Level), pressure gradient, and frequency peaks in the J-31 bomb bay at supersonic and subsonic speeds. Discusses whether the change of the internal physical quantity after the loading of one, two, or four missiles will cause flight hazards. The result of this research will help bomb bay designers to predict the frequency peaks and oscillations, which may create resonances and predict the occurrence of physical phenomena that may generate flight hazards. This research uses DES (Detached Eddy Simulation) and SST k-ω turbulence models to simulate the aerodynamic characteristics within the J-31 bomb bay. The simulation uses unstructured hexahedral meshes to divide the nodes and compare the simulation results with the AEDC (Arnold Engineering Development Center) wind tunnel experiment to increase the credibility of the research. The comparison results show that the numerical method can accurately predict the occurrence of any frequency peak within 2% of error, and show the pressure coefficient distribution prediction in the bomb bay is also similar to the experimental. The simulation results of this study in the J-31 bomb bay indicate that the loading of the missile will make the internal flow field more complicated, which will increase the internal pressure gradient and be more susceptible to the changes in the angle of attack, resulting in more severe disturbances. The results show that the loading of missiles will not increase the noise decibel number, and it is worth noting that the saw-toothed leading and trailing edges of the bomb bay will change the distribution of the maximum decibel numbers in the bomb bay. The free shear layer changed by the appearance of saw-toothed edges will result in a completely different sound field distribution.

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