Extrapolation of Jet Noise from the Geometric Near Field

由於實驗室的尺寸限制，使得飛機噴流噪音實驗只能取得幾何近場的實驗數據，造成與現實生活中所聽到的遠場噪音量測結果有落差。這份研究以點聲源外插法為核心，希望利用幾何近場的實驗數據建構一個具備近場特性且符合遠場觀察者眼中的虛擬點聲源模型，外插預測遠場噪音。幾何近場實驗數據提供了聲源強度、方向性關鍵訊息，遠場預測結果與實驗數據比較後，呈現高度準確性，特別是在高頻率、高速的噴流情況下。

關鍵字

噴流噪音；外插；遠場

並列摘要

Due to limited dimension of test chambers, the jet noise test is confined at geometric near field but the jet noise at far field is desired in practice. The aim of this study is to predict the jet noise at far field from the measured data in test chambers. This work focuses on the jet noise prediction at far field by extrapolating the measured data at geometric near field. A simple point source is employed to replace the whole jet source distribution to simplify the prediction and corresponds to the source image viewed from the eyes of observer at far field. However, the jet directivity is an inevitable issue for jet noise prediction because the point source is void of directivity. In other words, the point source is purely a monopole before modification. The information about directivity must be extracted from the measured data at geometric near field and be imposed on the point source to modify the prediction results. The modified predicted results show a remarkable agreement with measured data at far field, especially at high frequency band and high jet velocity.

並列關鍵字

jet noise ； extrapolation ； far-field

國際替代計量

Extrapolation of Jet Noise from the Geometric Near Field

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