Abstract
This study computationally evaluates the riblet drag reduction effect considering the effect of sweep angle. An implicit large eddy simulation is performed on a channel flow and an infinite swept wing. First, three different inclined angles between the riblets and the flow direction are tested in the channel flow. The results show that with increases in the inclined angle, the friction drag decreases, while the pressure drag increases approximately quadratically. The riblets with a 30° inclined angle increase the total drag of the channel flow. Then, an infinite wing with a 30° swept angle with and without riblets is studied. The riblets demonstrate satisfactory drag reduction efficiency because the cross flow over most parts of the wing is mild. The lift and friction drag follow the relation of the cosine law of a swept wing. Moreover, the cross flow and the turbulence fluctuation are suppressed by the riblets.
Highlights
The economic efficiency and energy consumption of a civil airplane in flight is directly related to the aerodynamic drag. a one-unit increase in the drag coefficient (∆CD = 0.0001) of the supersonicConcorde airplane was equal to a capacity of two passengers, i.e., approximately 2% of the total capacity [1]
The riblets demonstrate satisfactory drag reduction efficiency because the cross flow over most parts of the wing is mild
Studied the drag reduction effect of skewed wavy walls. They found that the friction drag reduction behaves approximately quadratically or linearly for different wavy walls, while the pressure drag always increases quadratically
Summary
An experiment of Sundaram et al, [20] showed that the drag reduction ratio of a swept wing decreases from 8% to 1% for the spanwise flow when the angle of attack increased from 0◦ to 6◦. When the flow angle is different from the riblet direction, additional pressure drag is induced. Studied the drag reduction effect of skewed wavy walls They found that the friction drag reduction behaves approximately quadratically or linearly for different wavy walls, while the pressure drag always increases quadratically. The drag reduction effects and the flow phenomena of the riblets in sweep angle are not clear. The drag reduction effects of a channel and an infinite swept wing were computationally studied. The drag reduction effect and Reynolds stress variation caused by riblets were analyzed
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