多色油墨法於大型空蝕水槽高速入流下模型表面流場可視化之發展與應用

DEVELOPMENT AND APPLICATION OF THE MULTI-COLOR INK TRACING METHOD TO SURFACE FLOW VISUALIZATIONS OF MODELS UNDER HIGH-SPEED INFLOW IN A LARGE CAVITATION TUNNEL

當應用先進的非侵入式光學流場量測技術於大型水槽之模型試驗時，仍因觀測距離長、模型表面反光、量測範圍-精度互制等因素，導致難以快速獲得模型大部分表面流場資訊。因此，本研究嘗試基於多色油墨法（multi-color ink tracing method）發展出適用於高速入流（high-speed inflow）的表面流場可視化（surface flow visualization）技術，並應用在國立臺灣海洋大學的大型空蝕水槽（Large Cavitation Tunnel，LCT）中之模型試驗。本研究先使用國立臺灣海洋大學的中型空蝕水槽（median cavitation tunnel，MCT）測試出適用於高速入流9.0 m/s下的油墨配方，之後再應用於大型空蝕水槽中長1.5 m之6：1橢球體模型上進行驗證；在−5.62度攻角及9.0 m/s入流的條件下，成功地呈現出層流邊界層（laminar boundary layer）經激紊器（turbulence stimulator）激發成紊流邊界層（turbulent boundary layer），以及橢球體尾部與刺狀支柱（sting）接合處之渦流結構。

When an advanced non-intrusive optical technique of flow measurement is applied to a model test in a large water tunnel, it is hard to rapidly acquire the global information of the flow upon the model surface because of long imaging distance, light reflection from the model surface, imaging range-accuracy coupling, etc. Therefore, this study attempted to develop a technique of surface flow visualization suitable for high-speed inflow condition based on the multi-color ink tracing method, and then apply to the model tests conducted in the Large Cavitation Tunnel (LCT) of National Taiwan Ocean University (NTOU). This study first used the Median Cavitation Tunnel (MCT) of NTOU to find out the ink formula suitable for the high-speed inflow of 9.0 m/s, and then applied to a 1.5 m long, 6:1 prolate spheroid model tested in the LCT for verification; under AoA =−5.62∘and 9.0 m/s inflow, the test results successfully demonstrated that the laminar boundary layer was tripped by a turbulence stimulator to become turbulent, and a vortical flow structure was formed at the juncture region of the spheroid aft part and the sting.