Drag reduction by herringbone riblet texture in direct numerical simulations of turbulent channel flow

Drag reduction by herringbone riblet texture in direct numerical simulations of turbulent channel flow

Benschop, H.O.G. (TU Delft Fluid Mechanics)
Breugem, W.P. (TU Delft Multi Phase Systems)

2017

A bird-feather-inspired herringbone riblet texture was investigated for turbulent drag reduction. The texture consists of blade riblets in a converging/diverging or herringbone pattern with spanwise wavelength Λf. The aim is to quantify the drag change for this texture as compared to a smooth wall and to study the underlying mechanisms. To that purpose, direct numerical simulations of turbulent flow in a channel with height Lz were performed. The Fukagata-Iwamoto-Kasagi identity for drag decomposition was extended to textured walls and was used to study the drag change mechanisms. For Λf/Lz ≳ O(10), the herringbone texture behaves similarly to a conventional parallel-riblet texture in yaw: the suppression of turbulent advective transport results in a slight drag reduction of 2%. For Λf/Lz ≲ O(1), the drag increases strongly with a maximum of 73%. This is attributed to enhanced mean and turbulent advection, which results from the strong secondary flow that forms over regions of riblet convergence/divergence. Hence, the employment of convergent/divergent riblets in the texture seems to be detrimental to turbulent drag reduction.

Drag reduction
riblets
direct numerical simulations

http://resolver.tudelft.nl/uuid:e8b67970-9238-43f9-b105-fa2a34161a1b

https://doi.org/10.1080/14685248.2017.1319951

1468-5248

Journal of Turbulence, 18 (8), 717 - 759

Institutional Repository

journal article

© 2017 H.O.G. Benschop, W.P. Breugem