Effect of drag reducing riblet surface on coherent structure in turbulent boundary layer |
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| Authors: | Guangyao CUI Chong PAN Di WU Qingqing YE Jinjun WANG |
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| Institution: | School of Aeronautical Science and Engineeting,Beihang University,Beijing 100083,China;Department of Aerodynamics,Wind Energy,Flight Performance&Propulsion,Delft University of Technology,NL-2629 HS Delft,Netherlands |
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| Abstract: | The characteristics of turbulent boundary layer over streamwise aligned drag reducing riblet surface under zero-pressure gradient are investigated using particle image velocimetry. The formation and distribution of large-scale coherent structures and their effect on momentum partition are analyzed using two-point correlation and probability density function. Compared with smooth surface, the streamwise riblets reduce the friction velocity and Reynolds stress in the turbulent boundary layer, indicating the drag reduction effect. Strong correlation has been found between the occurrence of hairpin vortices and the momentum distribution. The number and streamwise length scale of hairpin vortices decrease over streamwise riblet surface. The correlation between number of uniform momentum zones and Reynolds number remains the same as smooth surface. |
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| Keywords: | Corresponding author Coherent structures Particle image velocimetry Riblet Riblet surface Turbulent boundary layer Uniform momentum zones |
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