The magnetorotational instability is thought to be responsible for the generation of magnetohydrodynamic turbulence that leads to enhanced outward angular momentum transport in accretion discs. Here, we demonstrate that, during the exponential growth of the instability, the mean Reynolds stress is always positive, the mean Maxwell stress is always negative, and hence the total stress is positiv...

For inhomogeneous turbulent flows at high Reynolds number, it is shown that the redistribution term in Reynolds-stress turbulence models can be determined from the velocity–acceleration correlation. It is further shown that the drift coefficient in the generalized Langevin model (which is used in probability density function (PDF) methods) can be determined from the Reynolds stresses and the ve...

The performance of the large eddy simulation (LES) approach in predicting the evolution of a shear layer in the presence of stratification is evaluated. The LES uses a dynamic procedure to compute subgrid model coefficients based on filtered velocity and density fields. Two simulations at different Reynolds numbers are simulated on the same computational grid. The fine LES simulated at a low Re...

The residual-based variational multiscale formulation is applied to develop a large eddy simulation (LES) model for compressible flows. In addition, a mixed model, in which a deviatoric Smagorinsky subgrid stress term is added to the RBVM terms to better model the Reynolds stresses is proposed. These models, along with the dynamic Smagorinsky-Yoshizawa-eddy diffusivity model are tested in predi...

A numerical simulation to investigate the Non-Newtonian modeling effects on physiological flows in a three dimensional idealized artery with a single stenosis of 85% severity is given. The wall vessel is considered to be rigid. Oscillatory physiological and parabolic velocity profile has been imposed for inlet boundary condition. Determination of the physiological waveform is performed using a ...

Vegetation growing on the surface of a streambank has been shown to alter the shear stresses applied to the boundary, but basic questions remain regarding the influence of vegetation and streambank configurations on near-bank hydraulics. In the present study, Froudescaled flume experiments were used to investigate how changes in vegetation density (ratio of frontal area to channel area, includi...

The aim of this article is to numerically explore the effects a horizontal double layer trees (HDLT) across whole width channel on flow structures under steady rate and subcritical conditions. numerical domain was established in ANSYS Workbench, post-processing (i.e., meshing + boundary conditions) along with simulation carried out by utilizing computational fluid dynamics tool FLUENT. three-di...

Predictive capability of RANS and LES models to calculate incipient cavitation of water in a step nozzle is assessed. The RANS models namely, Realizable k-ɛ, SST k-ω and Reynolds Stress Model did not predict any cavitation, due to the limitation of RANS models to predict the low pressure vortex cores. LES WALE model was able to predict the cavitation by capturing the shear layer instability and...