کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
667828 | 1458597 | 2007 | 17 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Skin friction reduction by large air bubbles in a horizontal channel flow
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
مهندسی شیمی
جریان سیال و فرایندهای انتقال
پیش نمایش صفحه اول مقاله
چکیده انگلیسی
Microbubble and air film methods are believed to be applicable to skin friction reduction in ships. Small bubbles are dispersed into the turbulent boundary layer in the former case, and wide air layers cover the wall surface in the latter case. Previous studies did not specifically address the intermediate case between the microbubble and air film conditions. This study is concerned with the possibility and mechanism of drag reduction using relatively large air bubbles compared to the boundary layer thickness in a horizontal turbulent channel flow. The relationship between local skin friction and the bubble's interfacial structure is investigated by synchronizing the measurement of wall-shear stress with the image acquisition of bubbles. The bubble sizes range from 2 to 90Â mm approximately. As a result, a negative correlation between the local skin friction and the local void fraction is confirmed by the time-resolved measurement. A new observation is the fact that the local skin friction decreases drastically in the rear part of individual large bubbles, and rapidly increases after the bubble's rear interface passes. This characteristic underlies the bubble-size dependency of the average skin friction in the intermediate bubble size condition.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: International Journal of Multiphase Flow - Volume 33, Issue 2, February 2007, Pages 147-163
Journal: International Journal of Multiphase Flow - Volume 33, Issue 2, February 2007, Pages 147-163
نویسندگان
Yuichi Murai, Hiroshi Fukuda, Yoshihiko Oishi, Yoshiaki Kodama, Fujio Yamamoto,