Skin-friction reduction for the subsonic turbulent boundary layers

2014 Fiscal Year Final Research Report

• Project/Area Number: 24656518
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Aerospace engineering
• Research Institution: The University of Electro-Communications
• Principal Investigator: MAEKAWA Hiroshi 電気通信大学, 情報理工学(系)研究科, 教授 (90145459)
• Project Period (FY): 2012-04-01 – 2015-03-31
• Keywords: 乱流 / 摩擦抵抗低減 / 乱流境界層 / 亜音速

Outline of Final Research Achievements

The velocity and temperature profiles for the various supersonic turbulent boundary layers look very much the same, even though Mach numbers and heat-parameters differ considerably. The velocity profiles in the turbulent boundary layer follow a 1/7th power-law distribution quite well. In this study, based on this fact, the skin friction law of subsonic turbulent boundary layer on an isothermal wall is assumed to be described approximately as a power-law dependence given by Blasius law of Cｆ＝0.025（Reθ）＾（－m）, which is modified by the temperature ratio of （Te/Tw）＾（1－〈ｎ＋１〉ｍ）（２ｍ＋１）/(1+m), where m=1/4 and n=0.67. This skin friction law predicts the substantial drag reduction by (Te/Tw)＾0.7. The experiment shows that the velocity profiles are flowed by the 1/7th power-law distribution. The drag reduction prediction is coincident with the drag decrease up to 8.65% at Te/Tw=0.89 calculated by the measured velocity distribution using the log-law profile fitting.

Free Research Field

航空宇宙工学