Turbulent-Drag Reduction by Oblique Wavy Wall Undulations
Reducing the turbulent skin-friction drag over civilian aircraft is a potentially high-reward target, as this drag component accounts for about half of the total drag in cruise conditions. Thus, even modest reductions convert into material savings, resulting in significant cuts in costs. Active-control techniques can be remarkably effective at suppressing turbulence and drag, but pose major engineering challenges in terms of actuation, efficient operation, reliability and maintainability. In contrast, passive techniques based on riblets are easier to implement, but face important durability and maintenance limitations related to the extremely small spacing of the grooves. The alternative passive-control method that is the subject of the present paper was first proposed in Chernyshenko (Drag reduction by a solid wavy wall emulating spanwise oscillations. Part 1. [physics.flu-dyn](arXiv:1304.4638), (2013), ). The key characteristic of the method is that it involves wavy surface undulations directed obliquely to the mean flow and having wave lengths two orders of magnitude larger than riblets, and would thus be much more practical to manufacture and maintain.
The project was funded by Innovate UK (Technology Strategy Board), as part of the ALFET project, project reference 113022. The authors are grateful to the UK Turbulence Consortium (UKTC) for providing computational resources on the national supercomputing facility ARCHER under the EPSRC grant EP/L000261/1. Access to Imperial College High Performance Computing Service, doi: 10.14469/hpc/2232 is also acknowledged.
- 1.Chernyshenko, S.: Drag reduction by a solid wavy wall emulating spanwise oscillations. Part 1. [physics.flu-dyn](arXiv:1304.4638) (2013)