本計劃預備探討一旋轉軸之迴旋運動所產生的輻射噪音。計畫中將首先討論旋轉軸產生迴旋運動之引發機制，進行轉軸振動分析，並計算出轉軸表面每一點之速度分布狀況，其次利用聲場理論將轉軸表面的速度再轉換成壓力分布與壓力之梯度分布。由Efowcs Williams and Hawkings的聲源類比理論，轉軸迴旋運動產生的表面速度與壓力等物理性質，可以類比成為聲場中的單極聲源、偶極聲源和四極聲源的組合，這些聲源放入類比理論式中，即可得到轉軸迴旋運動之輻射聲場，轉動軸噪音可預計為轉動的複雜週期性函數，計畫中擬以Fourier series 處理。本研究將針對以上之作法進行理論性的探討，並撰寫程式求取數值解與結果討論，最後將進行系統參數分析。 ; This research will focus on the radiated noise due to the whirling motion of a rotating beam. The whirling vibration of a rotating beam subjected to external forces will be first investigated in the project. Then, the velocity and sound pressure profiles around the rotating beam can be derived. According to the method of acoustic analogy by Efowcs Williams and Hawkings, the velocity and sound pressure can be treated as monopoles, dipoles, and quardpoles in the radiated sound field. From this theory, the noise can be written as a complicated periodic function with the angular velocity same as the rotating angular velocity of the beam. The required sound field will be calculated from the above mentioned acoustic analogy theorem. Theoretical analysis of the problem and the associated parametric study will be conducted in this project. ; 研究期間 9808 ~ 9907
