scholarly journals Erratum: “A theoretical prediction of friction drag reduction in turbulent flow by superhydrophobic surfaces” [Phys. Fluids 18, 051703 (2006)]

2006 ◽  
Vol 18 (8) ◽  
pp. 089901 ◽  
Author(s):  
Koji Fukagata ◽  
Nobuhide Kasagi ◽  
Petros Koumoutsakos
Keyword(s):  
Theoretical Prediction ◽  
Turbulent Flow ◽  
Drag Reduction ◽  
Superhydrophobic Surfaces ◽  
Friction Drag ◽  
Friction Drag Reduction

Friction drag reduction based on a proportional-derivative control scheme

2021 ◽  
Vol 33 (7) ◽  
pp. 075115
Author(s):  
Chi Wai Wong ◽  
Xiaoqi Cheng ◽  
Dewei Fan ◽  
Wenfeng Li ◽  
Yu Zhou
Keyword(s):  
Drag Reduction ◽  
Friction Drag ◽  
Control Scheme ◽  
Friction Drag Reduction ◽  
Derivative Control

Turbulent flow over superhydrophobic surfaces with streamwise grooves

2014 ◽  
Vol 747 ◽  
pp. 186-217 ◽  
Author(s):  
S. Türk ◽  
G. Daschiel ◽  
A. Stroh ◽  
Y. Hasegawa ◽  
B. Frohnapfel
Keyword(s):  
Boundary Conditions ◽  
Turbulent Flow ◽  
Drag Reduction ◽  
Secondary Flow ◽  
Slip Length ◽  
Laminar Flows ◽  
Superhydrophobic Surfaces ◽  
Mean Velocity ◽  
Effective Slip Length ◽  
Effective Slip

AbstractWe investigate the effects of superhydrophobic surfaces (SHS) carrying streamwise grooves on the flow dynamics and the resultant drag reduction in a fully developed turbulent channel flow. The SHS is modelled as a flat boundary with alternating no-slip and free-slip conditions, and a series of direct numerical simulations is performed with systematically changing the spanwise periodicity of the streamwise grooves. In all computations, a constant pressure gradient condition is employed, so that the drag reduction effect is manifested by an increase of the bulk mean velocity. To capture the flow properties that are induced by the non-homogeneous boundary conditions the instantaneous turbulent flow is decomposed into the spatial-mean, coherent and random components. It is observed that the alternating no-slip and free-slip boundary conditions lead to the generation of Prandtl’s second kind of secondary flow characterized by coherent streamwise vortices. A mathematical relationship between the bulk mean velocity and different dynamical contributions, i.e. the effective slip length and additional turbulent losses over slip surfaces, reveals that the increase of the bulk mean velocity is mainly governed by the effective slip length. For a small spanwise periodicity of the streamwise grooves, the effective slip length in a turbulent flow agrees well with the analytical solution for laminar flows. Once the spanwise width of the free-slip area becomes larger than approximately 20 wall units, however, the effective slip length is significantly reduced from the laminar value due to the mixing caused by the underlying turbulence and secondary flow. Based on these results, we develop a simple model that allows estimating the gain due to a SHS in turbulent flows at practically high Reynolds numbers.

scholarly journals 710 Experimental Study on Friction Drag Reduction Effect of Flexible Tube(1)

2006 ◽  
Vol 2006 (0) ◽  
pp. _710-a_
Author(s):  
Zhigang GAO ◽  
Masatomo OHWAKI ◽  
Motoyuki ITOH ◽  
Shinji TAMANO ◽  
Kazuhiko YOKOTA
Keyword(s):  
Experimental Study ◽  
Drag Reduction ◽  
Friction Drag ◽  
Flexible Tube ◽  
Reduction Effect ◽  
Friction Drag Reduction
Sign in / Sign up

Export Citation Format

Share Document