We study transient growth in inertialess plane Couette and Poiseuille flows of viscoelastic fluids. For streamwise-constant three-dimensional fluctuations, we demonstrate analytically the existence of initial conditions that lead to quadratic scaling of both the kinetic energy density and the elastic energy with the Weissenberg number, We. This shows that in strongly elastic channel flows of vi...

The turbulent mass ux, or equivalently the uctuating Favre velocity mean, appears in the rst and second moment equations of compressible k " and Reynolds stress closures. Mathematically it is the di erence between the unweighted and density-weighted averages of the velocity eld and is therefore a measure of the e ects of compressibility through variations in density. It appears to be fundamenta...

This work presents a numerical technique for simulating incompressible, isothermal, viscoelastic flows of fluids governed by the upper-convected Maxwell (UCM) and K–BKZ (Kaye–Bernstein, Kearsley and Zapas) integral models. The numerical technique described herein is an extension of the GENSMAC method to the solution of the momentum and mass conservation equations to include integral constitutiv...

A simple theoretical analysis and direct numerical simulations on 512(3) grid points suggest that the velocity correlation spectrum tensor in the inertial subrange of homogeneous turbulent shear flow at high Reynolds number is given by a simple form that is an anisotropic function of the wave vector. The tensor is determined by the rate of the strain tensor of the mean flow, the rate of energy ...

While Reynolds-averaged Navier-Stokes (RANS) simulations remain the most affordable technique for simulating complex turbulent flows, the inability of linear eddy viscosity models to correctly predict flow separation and reattachment limits the reliability of the simulation outcome. A methodology to quantify the uncertainty in the simulation outcome related to the form of the turbulence model u...

Laser Doppler Velocimetry (LDV) has been employed to determine pseudo-turbulence characteristics of the flow field around bubble train forming in non-Newtonian caboxymethylcellulose (CMC) aqueous solution at low gas flow rate condition. The Reynolds stress and turbulent intensity of the liquid were investigated by means of Reynolds time-averaged method. The experimental results show that ax...

In the present paper, a new data-driven model is proposed to close and increase accuracy of Reynolds-averaged Navier–Stokes equations. Among variety turbulent quantities, it has been decided predict divergence Reynolds stress tensor (RST). Recent literature works highlighted potential this choice. The key novelty work obtain through neural network (NN) whose architecture input choice guarantee ...

It is shown that in self-preserving incompressible free shear flows governed by the boundary-layer equations, a region must exist which Reynolds-stress anisotropies are constant. The theoretical result confirmed an analysis of well-established experimental data for plane jet, axisymmetric and mixing layer. values corresponding determined, revealing differences between eigensystems these flows. ...

The characterisation of small-scale turbulence has been an active area research for decades and this includes, particularly, the analysis isotropy, as postulated by Kolmogorov. In particular, question if dissipation tensor is isotropic or not, how it related to anisotropy Reynolds stresses particular interest modelling purposes. While subject extensively studied in context isothermal flows, sit...

Microscopic structure in bubbly flows is a topic of interest in the study of fluid flows. In the present paper, the Ultrasonic Doppler Method was applied to the measurement of bubbly flows from which Reynolds stress profiles were obtained. Experiments were carried out for an air-water dispersed bubbly flow in a 20mm x 100 mm vertical rectangular channel having a void fraction smaller than 3%. T...