| Summary: | 碩士 === 國立中興大學 === 土木工程學系 === 90 === ABSTRACT
The present study is to make clear the characteristics of periodic oscillation flows over two-dimensional vertical drop energy-dissipators, using flow visualization technique, fiber laser Doppler velocimter (FLDV) and the wave gauge. Flow visualization technique of aluminum particle tracking method was used for qualitative observation and recognizing the phenomenon of periodic oscillation flow from the appearance of non-periodic oscillation flows, i.e., napped flow and skimming flow. Both fiber laser Doppler velocimeter and wave gauge were used for quantitative measurements. Spectrum analysis was used for calculating the fundamental frequency of oscillation flow.
As regard the case of the periodic oscillation flow, the important variables, which substantially affect the primary oscillation frequency of the periodic oscillation flow, include the critical velocity (Uc) and critical water depth (Yc) of the approaching flow, the gravity acceleration (g) of the free overfall, and the dimensions (L, H, h, Ls) and height difference (Δh) of the vertical drop energy-dissipator.
According to Buckingham π- theorem and the regression analysis, it is surprisingly found that two similar relationships between and and between and can be achieved. These two similar relationships are independent of the dimensions of the vertical drop energy-dissipator and conditions of the approaching flow.
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