Direct numerical simulations of turbulent flows over superhydrophobic surfaces

Direct numerical simulations (DNSs) are used to investigate the drag-reducing performance of superhydrophobic surfaces (SHSs) in turbulent channel flow. SHSs combine surface roughness with hydrophobicity and can, in some cases, support a shear-free air–water interface. Slip velocities, wall shear stresses and Reynolds stresses are considered for a variety of SHS microfeature geometry configurations at a friction Reynolds number of Reτ ≈ 180. For the largest microfeature spacing studied, an average slip velocity over 75% of the bulk velocity is obtained, and the wall shear stress reduction is found to be nearly 40%. The simulation results suggest that the mean velocity profile near the superhydrophobic wall continues to scale with the wall shear stress but is offset by a slip velocity that increases with increasing microfeature spacing.

[1]  Petros Koumoutsakos,et al.  A theoretical prediction of friction drag reduction in turbulent flow by superhydrophobic surfaces , 2006 .

[2]  Andrea Mammoli,et al.  Effective slip on textured superhydrophobic surfaces , 2005 .

[3]  P Tabeling,et al.  Slippage of water past superhydrophobic carbon nanotube forests in microchannels. , 2006, Physical review letters.

[4]  Kenneth S. Breuer,et al.  Turbulent Drag Reduction Using Superhydrophobic Surfaces , 2006 .

[5]  C. Meinhart,et al.  Apparent fluid slip at hydrophobic microchannel walls , 2002 .

[6]  John L. Lumley,et al.  Drag Reduction by Additives , 1969 .

[7]  Howard A. Stone,et al.  Effective slip in pressure-driven Stokes flow , 2003, Journal of Fluid Mechanics.

[8]  P. Moin,et al.  Suitability of upwind-biased finite difference schemes for large-eddy simulation of turbulent flows , 1997 .

[9]  Blair Perot,et al.  Laminar drag reduction in microchannels using ultrahydrophobic surfaces , 2004 .

[10]  제종두.  Direct numerical simulation of turbulent channel flow with permeable walls , 1999 .

[11]  David R. Dowling,et al.  Bubble friction drag reduction in a high-Reynolds-number flat-plate turbulent boundary layer , 2006, Journal of Fluid Mechanics.

[12]  B. Perot.  Conservation Properties of Unstructured Staggered Mesh Schemes , 2000 .

[13]  John Kim,et al.  DIRECT NUMERICAL SIMULATION OF TURBULENT CHANNEL FLOWS UP TO RE=590 , 1999 .

[14]  J. Rothstein,et al.  Direct velocity measurements of the flow past drag-reducing ultrahydrophobic surfaces , 2005 .

[15]  John Kim,et al.  Effects of hydrophobic surface on stability and transition , 2005 .

[16]  John Kim,et al.  Effects of hydrophobic surface on skin-friction drag , 2004 .

[17]  John Kim.  Active Control of Turbulent Boundary Layers for Drag Reduction , 1999 .

[18]  B. W. Webb,et al.  Fully developed electro-osmotic heat transfer in microchannels , 2003 .

[19]  D. W. Bechert,et al.  Experiments on drag-reducing surfaces and their optimization with an adjustable geometry , 1997, Journal of Fluid Mechanics.

[20]  Christophe Ybert,et al.  Achieving large slip with superhydrophobic surfaces: Scaling laws for generic geometries , 2007 .

[21]  J. R. Philip.  Integral properties of flows satisfying mixed no-slip and no-shear conditions , 1972 .

[22]  Michael B. Martell.  Simulations of Turbulence over Superhydrophobic Surfaces , 2009 .