Development of a turbulent boundary layer in a rotating square cross-section channel with relatively high local rotation parameter

• Published in: Experimental thermal and fluid science Vol. 86; pp. 85 - 97
• Main Authors: Wei, Kuan, Tao, Zhi, You, Ruquan, Wu, Huijie, Li, Haiwang
• Format: Journal Article
• Language: English
• Published: Philadelphia Elsevier Inc 01.09.2017; Elsevier Science Ltd
• Subjects: Angular velocity; Boundary layer; Coefficient of friction; Coriolis force; Cross-sections; Fluid flow; Friction; Hotwire; Influence; Kinematic viscosity; Local rotation parameter; Parameters; Penetration depth; Relaminarization; Reynolds number; Rotation channel; Studies; Thickness; Turbulent boundary layer; Velocity; Viscosity; Viscosity coefficient; Turbulent boundary layer; Local rotation parameter; Hotwire; Relaminarization; Rotation channel; Penetration depth
• ISSN: 0894-1777; 1879-2286
• DOI: 10.1016/j.expthermflusci.2017.04.006

•Developing turbulent flow with high local rotation parameter is studied.•A new explanation is given to the critical rotation number phenomenon.•A whole relaminarization process near the leading side is caught by experiment.•A new method is developed to determine the influence depth of the Coriolis force. The development of turbulent boundary layer in a rotating square cross-section straight channel were experimentally measured using hot wire in a new rotating facility. Measurements were conducted at four streamwise stations to study the development of turbulent boundary layer along the stream wise. The governing parameters of the boundary layer are local Reynolds number uτδ/ν and local rotation parameter Ων/uτ2 (uτ is the friction velocity, δ is the thickness of boundary layer, ν is the kinematic viscosity coefficient and Ω is the angular velocity of the channel, which is defined to be positive near the trailing side wall and negative near the leading side wall). The measurements are performed in the range of 199⩽uτδ/ν⩽367 and -0.0135⩽Ων/uτ2⩽0.0054 (these values correspond to u¯D/ν=19,000 and 0⩽|Ω|D/u¯⩽0.362, here, u¯ means the cross-section averaged streamwise velocity, and D means the hydraulic diameter of the channel). Due to the relatively high local rotation parameter |Ω|ν/uτ2 on the leading side (up to 0.0135), some new phenomena were discovered, such as the critical rotation number phenomenon revealed in the variations of wall friction coefficient (the critical rotation number ranges from 0.145 to 0.362), the so-called relaminarization process near the leading side wall. Moreover, in high local rotation parameter cases, the lower limit of the Coriolis force influenced region is too close to the wall to be recognized with the traditional method, hence a new method to evaluate the influence of Coriolis force was proposed in the present work.