We study the interplay between intrinsic rotation and internal transport barrier (ITB) dynamics through the dynamic change of the parallel Reynolds stress. Global flux-driven gyrofluid simulations are used for this study. In particular, we investigate the role of parallel velocity gradient instability (PVGI) in the ITB formation and the back transition. It is found that the excitation of PVGI i...

[1] This paper examines near-bottom shear stresses at two locations in a small, highly stratified estuary: the Navesink River, New Jersey, USA. The shear stresses obtained from acoustic Doppler current profilers (ADCPs) operating in the recently developed mode 11 at a high spatial resolution are examined in detail. Measurement noise of the ADCP is estimated using autocorrelation analyses and is...

An effect of a mean velocity shear on a turbulence and on the effective force which is determined by the gradient of the Reynolds stresses is studied. Generation of a mean vorticity in a homogeneous incompressible nonhelical turbulent flow with an imposed mean velocity shear due to an excitation of a large-scale instability is found. The instability is caused by a combined effect of the large-s...

We present a microfluidic rheometer that uses in situ pressure sensors to measure the viscosity of liquids at low Reynolds number. Viscosity is measured in a long, straight channel using a PDMS-based microfluidic device that consists of a channel layer and a sensing membrane integrated with an array of piezoresistive pressure sensors via plasma surface treatment. The micro-pressure sensor is fa...

A shear-improved Smagorinsky model is introduced based on recent results concerning shear effects in wall-bounded turbulence by Toschi et al. (2000). The Smagorinsky eddyviscosity is modified as νT = (Cs∆) (|S|−|〈S〉|): the magnitude of the mean shear |〈S〉| is subtracted to the magnitude of the instantaneous resolved strain-rate tensor |S|; here CS is the standard Smagorinsky constant and ∆ deno...

Toroidal magnetic fields subject to the Tayler instability can transport angular momentum. We show that the Maxwell and Reynolds stress of the nonaxisymmetric field pattern depend linearly on the shear in the cylindrical gap geometry. Resulting angular momentum transport also scales linear with shear. It is directed outwards for astrophysical relevant flows and directed inwards for superrotatin...

Computational experiments based on the direct numerical simulation of turbulent channel flow reveal that the skin friction can be reduced as much as 70% by the action of a localized steady force acting against the flow close to the wall. In addition, the excessive shear stresses observed during the laminar-to-turbulence transition can be substantially reduced. For a sustained reduction in the s...

A detailed review of recent developments in Reynolds stress modeling for incompressible turbulent shear ows is provided. The mathematical foundations of both two-equation models and full second-order closures are explored in depth. It is shown how these models can be systematically derived for two-dimensional mean turbulent ows that are close to equilibrium. A variety of examples are provided t...

An azimuthally symmetric radially sheared plasma fluid flow is observed to spontaneously form in a cylindrical magnetized helicon plasma device with no external sources of momentum input. A turbulent momentum conservation analysis shows that this shear flow is sustained by the Reynolds stress generated by collisional drift turbulence in the device. The results provide direct experimental suppor...

An experimental study with four different types of bed conditions was carried out to understand the effect of roughness in open channel flow at two different Reynolds numbers. The bed conditions include a smooth surface and three different roughness conditions, which were generated using sand grains with a median diameter of 2.46 mm. The three rough conditions include a surface with distributed...