We demonstrate an unexpected connection between isotropic turbulence and wall-bounded shear flows. We perform direct numerical simulations of isotropic turbulence forced at large scales at moderate Reynolds numbers and observe sudden transitions from a chaotic dynamics to a spatially simple flow, analogous to the laminar state in wall bounded shear flows. We find that the survival probabilities...

A total of four moorings from POLYMODE Array I and II were analyzed in an investigation of internal wavefield-mean flow interactions. In particular, evidence for wave-mean flow interaction was sought by searching for time correlations between the wavefield vertically-acting Reynolds stress (estimated using the temperature and velocity records), and the mean shear. No significant stress-shear co...

The flow separation taking place over the forward-facing step is measured by high-resolution PIV using long-range microscope. The step has height of h=10 mm and the free stream velocity is 20 m/s, resulting in a Reynolds number of Reh=13,700. Two separation bubbles are produced in the immediate upstream and downstream of the step respectively. The upstream separation has a length of 0.6h, while...

Fully developed turbulent and laminar flows through symmetric planar and axisymmetric expansions with heat transfer were modeled using a finite-difference discretization of the boundary-layer equations. By using the boundary-layer equations to model separated flow in place of the Navier-Stokes equations, computational effort was reduced permitting turbulence modeling studies to be economically ...

The shear flow of non-Brownian glass spheres suspended in a concentrated colloidal dispersion that exhibits non-Newtonian rheology is investigated. At low volume fractions, the addition of non-Brownian spherical particles to the colloidal dispersion leads to an increase in the shear viscosity as well as the dynamic moduli. The flow curves of these suspensions are qualitatively similar to the su...

The logarithmic region, also referred to as the inertial subrange in physical space, or the turbulent wall region, is arguably the most important region of wall-bounded turbulent flows due to the multi-scale processes that take place. In this paper we review recent studies that report on the universality of this region in terms of the scaling laws for the mean velocities and turbulence intensit...

Simulations of three-dimensional laminar forced convection in a plane symmetric sudden expansion are presented for Reynolds numbers where the flow is steady and symmetric. A swirling ‘‘jetlike’’ flow develops near the sidewalls in the separating shear layer, and its impingement on the stepped wall is responsible for the maximum that develops in the Nusselt number adjacent to the sidewalls and f...

This paper shows that the turbulent velocity profile for zero-pressure-gradient boundary layers is affected by the wall shear stress and convective inertia. The effect of the wall shear stress is dominant in the so-called overlap region and can be described by a logarithmic law in which the von Karman constant is about 0.4 while the additive constant depends on a Reynolds number. The effect of ...

Aims. We study the dependence of turbulent transport coefficients, such as α effect and turbulent magnetic diffusivity, on shear and magnetic Reynolds number in the presence of helical forcing. Methods. We use three-dimensional direct numerical simulations with periodic boundary conditions and measure turbulent transport coefficients using the kinematic test field method. In all cases the magne...

– We study the strain response to steady imposed stress in a spatially homogeneous, scalar model for shear thickening, in which the local rate of yielding Γ(l) of mesoscopic ‘elastic elements’ is not monotonic in the local strain l. Despite this, the macroscopic, steady-state flow curve (stress vs. strain rate) is monotonic. However, for a broad class of Γ(l), the response to steady stress is n...