Note on a Parametric Relation for Separating Flow over a Rough Hill

Loureiro, Juliana; Freire, Atila P. Silva

doi:10.1007/s10546-009-9362-x

Cited by 11 publications

(6 citation statements)

References 20 publications

(37 reference statements)

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“…For instance, the modified log-layer assumption derived by Fourrière et al (2007) could be applied, where both the local pressure gradient and the surface roughness are considered in deriving the mean velocity profile. A similar equation has been found by Loureiro et al (2008) and Loureiro and Freire (2009) to be experimentally correct.…”

Section: Vertical Profilessupporting

confidence: 81%

Large eddy simulation of sediment transport over rippled beds

Harris

Grilli

2014

Nonlin. Processes Geophys.

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Abstract. Wave-induced boundary layer (BL) flows over sandy rippled bottoms are studied using a numerical model that applies a one-way coupling of a "far-field" inviscid flow model to a "near-field" large eddy simulation (LES) NavierStokes (NS) model. The incident inviscid velocity and pressure fields force the LES, in which near-field, wave-induced, turbulent bottom BL flows are simulated. A sediment suspension and transport model is embedded within the coupled flow model. The numerical implementation of the various models has been reported elsewhere, where we showed that the LES was able to accurately simulate both mean flow and turbulent statistics for oscillatory BL flows over a flat, rough bed. Here we show that the model accurately predicts the mean velocity fields and suspended sediment concentration for oscillatory flows over full-scale vortex ripples. Tests show that surface roughness has a significant effect on the results. Beyond increasing our insight into wave-induced oscillatory bottom BL physics, sophisticated coupled models of sediment transport such as that presented have the potential to make quantitative predictions of sediment transport and erosion/accretion around partly buried objects in the bottom, which is important for a vast array of bottom deployed instrumentation and other practical ocean engineering problems.

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Section: Vertical Profilessupporting

confidence: 81%

Large eddy simulation of sediment transport over rippled beds

Harris

Grilli

2014

Nonlin. Processes Geophys.

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“…(a) first-order equations, (b) second-order equations, (92) The solutions of the above equations are:…”

Section: Transpired Near Wall Solution For the κ-ǫ Modelmentioning

confidence: 99%

The persistence of logarithmic solutions in turbulent boundary layer systems

Freire

2015

J Braz. Soc. Mech. Sci. Eng.

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from the first principles of mechanics and the formalism of a continuous field characterized by density and viscosity.Thus, the complete absence of a comprehensive theory that can convincingly deal with disordered flows may come to many as a surprise. The crux of the matter, obviously, is the strong non-linear character of the advection terms in the equations of motion. Under certain conditions-in particular, high Reynolds numbers-fluid flows become unstable, growing rapidly to a complicated and confused state that is termed turbulent and has a large number of degrees of freedom.In fact, it can be argued that an exact and detailed description of the manner in which a turbulent flow evolves is physically meaningless due to the inherent difficulty in specifying its boundary and initial conditions for situations that are of interest in practical problems. A microscopic account of the flow behavior is certainly relevant for the understanding of local and instantaneous irregularities, but what is normally of real interest is the behavior of the macroscopic regularities of the flow. Therefore, it seems that the appropriate description of a turbulent flow needs to resort to statistical methods.Provided the irregular variation of the flow properties can be averaged over, say, some interval of time, the field properties can be decomposed into smoothed out (mean part) and rapidly varying quantities (fluctuating part). Once this procedure is accepted, substitution of the decomposed field variables into the Navier-Stokes equations results in a new equation for the mean variables, but with additional terms involving double correlations of the fluctuations, quantities that are formally unknown and that, hence, require modeling. The resulting second-order tensor-the Reynolds stress tensor-represents the transport of momentum due to the turbulent fluctuations and has the Abstract The present work studies the prevalence of logarithmic solutions in the near wall region of turbulent boundary layers. Local solutions for flows subject to such diverse effects as compressibility, wall transpiration, heat transfer, roughness, separation, shock waves, unsteadiness, non-Newtonian fluids or a combination of these factors are discussed. The work also analyzes eleven different propositions by several authors for the near wall description of the mean velocity profile for the incompressible zero-pressuregradient turbulent boundary layer. The asymptotic structure of the flow is discussed from the point of view of double limit processes. Cases of interest include attached and separated flows for the velocity and temperature fields.

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“…The above results show that the turbulent boundary layer of a power-law fluid exhibits a canonical two-deck structure defined by the principal equations, Eqs. (27) and (29). The viscosity of the fluid defines the thickness of the viscous region through…”

Section: Perturbation Analysis: Morphological Structurementioning

confidence: 99%

“…To estimate the value of B n in Eq. (11) the procedure adopted in Loureiro et al [28] and Loureiro and Silva Freire [29] was repeated here. Global optimization algorithms based on direct search methods were used.…”

Section: Law Of the Wall: Power-law Fluidmentioning

confidence: 99%

Asymptotic analysis of turbulent boundary-layer flow of purely viscous non-Newtonian fluids

Loureiro

Freire

2013

Journal of Non-Newtonian Fluid Mechanics

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The asymptotic structure of turbulent boundary layers of purely viscous non-Newtonian systems is investigated through the intermediate variable technique. The cases of power-law and Carreau fluids are discussed in detail. Results show that a classical two-layered structure persists, with a viscous layer thickness that is dependent on the power-law index, n, and a logarithmic solution in the fully turbulent region. For Carreau fluids, in general, a three-layered structure emerges, with two nested viscous sub-layers. Experimental and numerical data from other authors are used to determine the functional behaviour of the linear coefficient of the log-law with n.

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Note on a Parametric Relation for Separating Flow over a Rough Hill

Cited by 11 publications

References 20 publications

Large eddy simulation of sediment transport over rippled beds

Large eddy simulation of sediment transport over rippled beds

The persistence of logarithmic solutions in turbulent boundary layer systems

Asymptotic analysis of turbulent boundary-layer flow of purely viscous non-Newtonian fluids

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