Turbulent models provide closure equations that relate the Reynolds stress with kinematic tensors. In this study, we present a methodology to quantify dependence of tensor on mean basis. The is based upon decomposition theorems which allow extract from anisotropic part linear or nonlinear in strain rate D, and parts are in-phase (sharing same eigenvectors) out-of-phase rate. study was conducted using direct numerical simulation (DNS) data for turbulent plane channel (from Re τ=180 τ=1000)...

Low turbulent Reynolds number direct simulation data are used to calculate the invariants of stress and dissipation rate in a square duct. The results show that, depending on region where analysis is carried out, flow field comes close one-, two-, three-component states. Modeling such flows—even at higher numbers—will require models that can approach all three A related nonlinear k-ε tested priori using data. numerical averaged Navier–Stokes equations with these was performed. Their ability...

We report on temporal large eddy simulations (TLES) of the turbulent channel flow a dilute polymer solution modeled with FENE-P (finitely extensible nonlinear elastic in Peterlin approximation) constitutive equation. The are based upon an approximate deconvolution method [Pruett et al., Phys. Fluids, 18, 028104–1, (2006)] for residual Newtonian stress modeling and secondary regularization unresolved subfilter stress. filtered conformation tensor equation involves stretching spring force, as...

Abstract It is well known that the addition of minute amounts long polymer chains to organic solvents, or water, can lead significant turbulent drag reduction. In present study, direct numerical simulations channel flow a viscoelastic fluid, at zero-shear friction Reynolds numbers up 1000, are analyzed. Both mean and fields studied, but with primary focus on stress extra-stress (conformation tensor) in order contrast dynamics each. An analysis both kinetic energy elastic budget made,...

The polymer coil–stretch mechanism in turbulent drag reducing flows is analysed using direct numerical simulations of viscoelastic finitely extensible nonlinear elastic fluids with the Peterlin approximation. study carried out taking into account low and high reduction regimes. stretching alignment between conformation tensor other relevant entities are investigated statistical analysis. significant former velocity fluctuations product indicates that initial due to mean shear increased by...

The active and hibernating turbulence in drag-reducing plane Couette flows is analyzed. qualitative picture that emerges from the investigation a cyclic mechanism of energy exchange between polymers drives flow through an oscillatory behavior.

Four classic criteria used to the classification of complex flows are discussed here. These useful identify regions flow related shear, elongation or rigid-body motion. usual criteria, namely $Q$, $\Delta$, $\lambda_{2}$ and $\lambda_{cr}/\lambda_{ci}$, use fluid's rate-of-rotation tensor, which is known vary with respect a reference frame. The advantages using objective (invariant general transformation on frame) in present work. In this connection, we construct versions replacing standard...

In the present paper, we investigate polymer–turbulence interaction by discriminating between mechanical responses of this system to three different subdomains: elliptical, parabolic, and hyperbolic, corresponding regions where magnitude vorticity is greater than, equal to, or less than rate strain, respectively, in accordance with Q-criterion. Recently, it was recognized that hyperbolic structures play a crucial role drag reduction phenomenon viscoelastic turbulent flows, thanks observation...

An analysis of the spectral turbulent kinetic energy budget in a fully developed plane channel flow is performed. Direct numerical simulation data are evaluated at friction Reynolds numbers Reτ 180 and 1000. The focused on influence number cascade corresponding physical space presence inhomogeneity anisotropy. distribution compared for both numbers, relevant characteristics transfer process wall-bounded described. Differences noted between low high wavenumbers. results further assessed with...

The present paper provides an analysis of the statistical uncertainties associated with direct numerical simulation (DNS) results and experimental data for turbulent channel pipe flows, showing a new physically based quantification these errors, to improve determination deviations between DNSs experiments. is carried out using recently proposed criterion by Thompson et al. [“A methodology evaluate errors in DNS plane flows,” Comput. Fluids 130, 1–7 (2016)] fully where mean velocity error...

The transition from laminar to turbulent flows has challenged the scientific community since seminal work of Reynolds ( Phil. Trans. R. Soc. Lond. A, vol. 174, 1883, pp. 935–982). Recently, experimental and numerical investigations on this matter have demonstrated that spatio-temporal dynamics are associated with transitional belong directed percolation class. In present work, we explore analysis laminar–turbulent perspective recent theoretical development concerns viscoelastic turbulence,...

Tensorial decompositions and projections are used to study the performance of algebraic non-linear models predict anisotropy Reynolds stresses. Direct numerical simulation (DNS) data for plane channel flows at friction number (Reτ = 180, 395, 590, 1000), boundary layer using both DNS 359, 830, 1271) experimental 2680, 3891, 4941, 7164) build evaluate models. These projected into tensorial basis formed from symmetric part mean velocity gradient non-persistence-of-straining tensor. Six...