臺灣國際科展

消波一線牽-花蓮港港池共振

科展類別
臺灣國際科展
屆次
2007年
科別
地球與太空科學
學校名稱
國立臺南第一高級中學
指導老師
鄧明聖、邱文光
作者
吳宗祐、陳政瑜
關鍵字
花蓮港 共振

摘要或動機

本實驗利用喇叭、鍍鉑黑電極、波型產生器、鎖相放大器、及sciworkshope750 介面卡組合一套系統,此系統可使偵測精密度大幅提升,使得花蓮港模型尺度變小(120×60×4cm),因此可節省實驗的成本與時間。本實驗希望藉由模型的建立,感測系統的整合,傅立葉分析,使研究者可在各種模型條件下,獲得水波傳遞的相關物理量。鑒於花蓮港喇叭狀港池經實驗後證明容易造成港內共振,且不同的入射波頻率不同,所造成的共振現象及共振位置相當複?。本實驗為縮小模型,但卻可測出的共振頻率、衰退時間及振幅且非常明顯(精密度達3.0×10-4cm/mV)。首要課題是要在港內消除反射的波,在模型實驗中,測量有無加消波線及加不同材質
的線時波衰退時間的長短,得到衰退時間牽線消波者比實驗組減少為0.2-0.6 之間;振幅減少為0.03-0.89 之間,且越鬆散、分支越多、孔隙越大的物質消波狀況越佳,所以毛線效果最佳,棉線次之而尼龍繩最差。
This study utilizes the loudspeaker, the platinum-plated electrode, Sweep Function Generators, DSP Lock-in Amplifier, and the sciworkshope750 interface to construct our system. The system will enhance the great precision of detection, which diminishes the Hualien Harbor model yardstick to 120*60*4(cm). Thus we can save the cost and time of the experiments. We combine the setting-up of the model, the integration of the sensors and the Fast Fourier Transform (FFT) system so that the researchers can obtain the physics-related data when the water transmits ripples in various kinds of conditions. Seeing that the bell-shaped Hualien Harbor is apt to cause resonance in its basin, which is confirmed by our experiments later, our primary goal is to find a way to diminish the waves reflected in the harbor. With the diverse frequencies of incident waves, resultant resonance phenomena and positions are rather complicated. Our experiments are based on a miniature model, but the resonance frequency, the time of wave declining and the wave amplitude are easily measured, with the precision up to 3.0×10-4cm/mV. In another experiment, we add strings made of different materials that can subdue waves. Compared with the records without strings, the strings can reduce the time of wave declining by
0.2-0.6 and can reduce the amplitude by 0.03- 0.89. We have come to the conclusion that strings made of looser, more-branching and bigger-interstice material perform better in diminishing waves. Hence, the knitting wool has the best results, followed by the cotton threads and then the nylon ropes.


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