A near-wall subgrid-scale (SGS) model is used to perform large-eddy simulation (LES) of the developing, smooth-wall, zero-pressure-gradient flat-plate turbulent boundary layer. In this model, the stretched-vortex, SGS closure is utilized in conjunction with a tailored, near-wall model designed to incorporate anisotropic vorticity scales in the presence of the wall. Large-eddy simulations of the turbulent boundary layer are reported at Reynolds numbers Re θ based on the free-stream velocity and the momentum thickness in the range Re θ = 10 3 -10 12. Results include the inverse squareroot skin-friction coefficient, 2/C f , velocity profiles, the shape factor H, the von Kármán 'constant' and the Coles wake factor as functions of Re θ . Comparisons with some direct numerical simulation (DNS) and experiment are made including turbulent intensity data from atmospheric-layer measurements at Re θ = O(10 6 ). At extremely large Re θ , the empirical Coles-Fernholz relation for skin-friction coefficient provides a reasonable representation of the LES predictions. While the present LES methodology cannot probe the structure of the near-wall region, the present results show turbulence intensities that scale on the wall-friction velocity and on the Clauser length scale over almost all of the outer boundary layer. It is argued that LES is suggestive of the asymptotic, infinite Reynolds number limit for the smooth-wall turbulent boundary layer and different ways in which this limit can be approached are discussed. The maximum Re θ of the present simulations appears to be limited by machine precision and it is speculated, but not demonstrated, that even larger Re θ could be achieved with quad-or higher-precision arithmetic.

Stability of passive locomotion in inviscid wakesPhys. Fluids 25, 021901 (2013) Energy spectra and turbulence generation in the wake of magnetic obstacles Phys. Fluids 24, 115111 (2012) Three-dimensional wake transition behind an inclined flat plate Phys. Fluids 24, 094107 (2012) Vortex shedding in flow past an inclined flat plate at high incidence Phys. Fluids 24, 084103 (2012) About turbulence statistics in the outer part of a boundary layer developing over two-dimensional surface roughness Phys. Fluids 24, 075112 (2012) Additional information on Phys. Fluids

Symmetry analysis and self-similar forms of fluid flow and heat-mass transfer in turbulent boundary layer flow of a nanofluid Phys. Fluids 24, 092003 (2012) Detuned resonances of Tollmien-Schlichting waves in an airfoil boundary layer: Experiment, theory, and direct numerical simulation Phys. Fluids 24, 094103 (2012) Asymptotic expansion of the solution of the steady Stokes equation with variable viscosity in a two-dimensional tube structure J. Math. Phys. 53, 103702 (2012) Large-eddy simulation of turbulent channel flow using explicit filtering and dynamic mixed models Phys. Fluids 24, 085105 (2012) Additional information on Phys. Fluids Large eddy simulation (LES) is reported for both smooth and rough-wall channel flows at resolutions for which the roughness is subgrid. The stretched vortex, subgridscale model is combined with an existing wall-model that calculates the local friction velocity dynamically while providing a Dirichlet-like slip velocity at a slightly raised wall. This wall model is presently extended to include the effects of subgrid wall roughness by the incorporation of the Hama's roughness function U + (k + s∞ ) that depends on some geometric roughness height k s∞ scaled in inner variables. Presently Colebrook's empirical roughness function is used but the model can utilize any given function of an arbitrary number of inner-scaled, roughness length parameters. This approach requires no change to the interior LES and can handle both smooth and rough walls. The LES is applied to fully turbulent, smooth, and rough-wall channel flow in both the transitional and fully rough regimes. Both roughness and Reynolds number effects are captured for Reynolds numbers Re b based on the bulk flow speed in the range 10 4 -10 10 with the equivalent Re τ , based on the wall-drag velocity u τ varying from 650 to 10 8 . Results include a Moody-like diagram for the friction factor f = f(Re b , ), = k s∞ /δ, mean velocity profiles, and turbulence statistics. In the fully rough regime, at sufficiently large Re b , the mean velocity profiles show collapse in outer variables onto a roughness modified, universal, velocity-deficit profile. Outer-flow stream-wise turbulence intensities scale well with u τ for both smooth and rough-wall flow, showing a log-like profile. The infinite Reynolds number limits of both smooth and rough-wall flows are explored. An assumption that, for smooth-wall flow, the turbulence intensities scaled on u τ are bounded above by the sum of a logarithmic profile plus a finite function across the whole channel suggests that the infinite Re b limit is inviscid slip flow without turbulence. The asymptote, however, is extremely slow. Turbulent rough-wall flow that conforms to the Hama model shows a finite limit containing turbulence intensities that scale on the friction factor for any small but finite roughness. C 2012 American Institute of Physics.

Symmetry analysis and self-similar forms of fluid flow and heat-mass transfer in turbulent boundary layer flow of a nanofluid Phys. Fluids 24, 092003 (2012) Detuned resonances of Tollmien-Schlichting waves in an airfoil boundary layer: Experiment, theory, and direct numerical simulation Phys. Fluids 24, 094103 (2012) Asymptotic expansion of the solution of the steady Stokes equation with variable viscosity in a two-dimensional tube structure J. Math. Phys. 53, 103702 (2012) Large-eddy simulation of turbulent channel flow using explicit filtering and dynamic mixed models Phys. Fluids 24, 085105 (2012) Additional information on Phys. Fluids (2010)] to calculate the statistics of the fluctuating streamwise velocity in the inner region. Results, including spectra and moments up to fourth order, are compared with equivalent predictions using experimental time series, as well as with direct experimental measurements at Reynolds numbers Re τ = 7300, 13 600, and 19 000. The LES combined with the wall model are then used to extend the inner-layer predictions to Reynolds numbers Re τ = 62 000, 100 000, and 200 000 that lie within a gap in log (Re τ ) space between laboratory measurements and surface-layer, atmospheric experiments. The present results support a loglike increase in the near-wall peak of the streamwise turbulence intensities with Re τ and also provide a means of extending LES results at large Reynolds numbers to the nearwall region of wall-bounded turbulent flows. C 2012 American Institute of Physics.

An arrangement of a large-eddy simulation (LES) is described that facilitates a spatially developing thermally stratified atmospheric boundary layer (ABL). When the inflow and outflow boundary conditions are specified, the LES of stably stratified ABL turns out to be challenging because spurious reflections of waves at the boundary accumulate inside the domain. To tackle this problem, a fringe method with an auxiliary LES running concurrently is applied to enforce upstream/downstream boundary conditions. An artificial forcing term is applied within a fringe region located at the beginning of the main LES domain in order to ensure statistically stationary inflow boundary conditions. The auxiliary LES, which is horizontally homogeneous in a doubly periodic domain, is used to determine the inflow condition of the main LES domain. The present scheme is used to provide an Eulerian perspective of the stratocumulus to shallow cumulus cloud (Sc–Cu) transition, one of the key cloud regimes over the subtropical ocean. In this study, the transition is triggered by increasing the sea surface temperature (SST) and the LES runs until a statistically steady evolution of the Sc–Cu transition is achieved. The flow statistics are compared with those from a recycling-type method and it is found that the fringe method is more suitable for the current applications.