影像辨識應用在油墨流線的數位化與其應用

Application of Streamline Digitalization on Ship Model Ink Paint Test

在拖航水槽進行油墨試驗取得的油墨流線可提供船體周圍流線的資訊，但是以拍照或錄影方式留下的二維影像記錄只能用肉眼觀察，無法得到具體數據，若將油墨流線加以數位化並與船模曲面結合，便能作數值分析相關研究。本研究開發一套「油墨流線資訊數位化系統」，運用影像處理的手法辨識油墨流線的形狀與位置，以事先佈置的定位用標記，依序連結多張相片，然後將這些數位數據套疊到船模表面。首先以一艘表面有多條平行水線的船模進行水線辨識，確認本系統的準確度，接著使用本系統對油墨試驗船模進行油墨流線辨識，最終順利得到含有油墨流線的數位化3D船模檔。這個檔案顯示在銀幕上，可以自由地移動、翻轉、放大、縮小、複製、攜帶、傳送，提供視覺觀察與數值分析的應用。最後進行計算流體力學(CFD)取得的模擬流線，與本系統得到的數位化油墨流線比較，分析其差異量，並建立一個模擬與試驗流線的比較方法。

"The ship model ink paint test shows the streamline on the model surface, which indicate the situation of the flu-id flow around the ship hull. The valuable information, however, can only be recorded by photos or videos currently. Those recorded analogic visual images provide few information and are incapable for mathematical analysis. In this study, we convert the ink streamline photos taken from ink paint test into digitalized data by means of image processing technology, that make us able to perform further analysis and application. First of all, a streamline identification program is developed, in which Gaussian filter is used for photo prepro-cessing, and HSV color value is applied to identify the black ink streamline from the background color of yellow. Because it needs twenty pictures along the longitudinal direction to compose the total ink streamline, a pair of round markers to connect two continuous photos are introduced to perform the precious linkage of each other. After the identification process, the ink streamlines is converted into digitalized data and is attached on the surface of ship model. Once the coordinates of the ink streamline joint together with the ship model, one can then use drawing software to do zoom in/out, rotation, copy, distribute and etc. easily, which means the information from ink paint test can be shared with multiple personal. In order to understand the effectiveness of the digitalized ink streamline on the mathematical analysis, the simu-lated streamlines calculation by using CFD software is carried out. After a serial of comparison and analysis, it shows that the digitalized ink streamline data is effective in research purpose."