摘要

本研究藉由實驗方法，研究振盪噴流通過平板時(亦即振盪壁面噴流)的流場特徵行為與熱傳特性。本研究發展一合成噴流產生振盪噴流，此合成噴流經由兩個獨立開口產生周期性的吹氣與吸氣。藉由調整合成噴流的制動參數，控制合成噴流的振盪特性，其中包含速度振盪頻率、速度振盪振幅、速度擾動強度及平均速度值。相關振盪噴流的振盪特性，使用熱線風速儀偵測。將不同振盪特性的振盪噴流與平板結合，使得流過平板的合成噴流與平板相切，研究平板上方之流場的特徵行為及熱傳特性。在執行流場觀察實驗時，使用壓克力平板;然而，在執行熱傳實驗時，使用加熱平板。應用流場可視化的技術，在不同的振盪條件之下，觀察振盪噴流經過平板上方的流場行為，時間上及空間上之平板上方的流場特徵行為將被呈現。使用質點影像速度儀量化平板上方的流場特徵結構之全域速度場，同時，在平板上方的速度向量與流線圖都予以量化。使用紅外線熱顯像系統量測加熱平板上方的溫度分佈，針對不同的振盪特性，計算平板上方的熱對流係數與紐塞爾數，探討平板上方的流場特徵與熱傳性能之間的關係。

ABSTRACT

The flow and heat transfer characteristics of the pulsating jets flowing tangentially over a flat plate (i.e. pulsating wall jets) were experimentally investigated. A synthetic jet was developed in this study to produce the pulsating jets. This synthetic jet produced periodic ejection and suction of fluid from two respective openings. The jet pulsation properties of the pulsating jets, which include frequency, amplitude, and mean value of jet pulsation, were measured by hot-wire anemometer. The pulsating jets blew tangential along a flat plate. The flow characteristics were performed with an acrylic plate, while the heat transfer experiments were conducted with a heated plate. The effect of varying jet pulsation properties on the flow characteristics above the flat plate will be studied by flow visualization. The temporal and spatial evolution processes of the characteristic flow behavior on the flat plate were revealed. The velocity field on the flat plate at various characteristic flow modes will be quantified by employing the PIV technique. The velocity vector and streamline patterns on flat plate at various pulsating properties were simultaneously presented and discussed. The temperature distribution on the surface of the heated plate was scanned by an infrared imaging system. The convection heat transfer coefficients and Nusselt numbers of the pulsating wall jets at various pulsation properties were further calculated. The correlation between the flow characteristic and heat transfer performance were discussed.

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