Figure 2 shows the geometry of a ty

Figure 2 shows the geometry of a typical saw-tooth serration, where 2h is the serration height (or amplitude), λ is the width, and Ɵ is the inclined angle. According to Howe10, in order to use the saw-tooth serration at the propeller trailing edge to reduce noise, some important geometry parameters need to be considered. The ratio between half height of the serration and the boundary layer thickness at trailing edge (h/δ) should larger than 0.25, otherwise the amplitude of the serration would be too small, and the turbulent eddies would pass over the saw-tooth without significant interaction. Thus, the system will experience no noise reduction. Secondly, the inclined angle should smaller than 45 degrees, which means the width/height ratio (λ/h) of the serration will smaller than 4.

結果 (繁體中文) 1:

圖2示出一個典型的鋸齒的鋸齒，其中2H是鋸齒高度（或振幅）的幾何形狀，λ是寬度，Ɵ是傾斜角度，根據Howe10，為了使用鋸齒的鋸齒在螺旋槳尾緣，以降低噪聲，一些重要幾何參數需要被考慮。鋸齒的一半高度與邊界層厚度之間的比率在後緣（H /δ）應大於0.25，否則鋸齒的幅度將太小，並且湍流漩渦會越過鋸齒沒有顯著的相互作用。因此，系統將經歷無噪音的降低。其次，傾斜角應小於45度，這意味著寬/高比（λ/鋸齒將小於4的小時）。

結果 (繁體中文) 2:

Figure 2 shows the geometry of a typical saw-tooth serration, where 2h is the serration height (or amplitude), λ is the width, and Ɵ is the inclined angle. 在《至何利日》中， 有一則是《》， 「十一十九八九年十分， 「十一月二十九日》 The ratio between half height of the serration and the boundary layer thickness at trailing edge (h/δ) should larger than 0.25, otherwise the amplitude of the serration would be too small, and the turbulent eddies would pass over the saw-tooth without significant interaction。 Thus， system will experience no noise reduction。 二月， inclined angle should smaller than 45 degrees， which means width/height ratio （h）

結果 (繁體中文) 3:

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