The 1877 assumption/conjecture of Boussinesq is that turbulent fluctuations have a dissipative effect on the mean flow. The eddy viscosity hypothesis is that this dissipative effect can be modelled by a turbulent viscosity term. Many computational and experimental data sets have shown that the eddy viscosity hypothesis is not generally correct. The inverse cascade of energy to larger scales in ...

This paper presents a stability, convergence and error analysis for two modular, projection-based variational multiscale (VMS) methods for the incompressible Naiver-Stokes equations. In VMS methods, the influence of the unresolved scales onto the resolved small scales is modeled by a Smagorinsky-type turbulent viscosity acting only on the marginally resolved scales. We analyze a method of induc...

Oil droplet transport under a non-breaking deep water wave field is investigated herein using Computational Fluid dynamics (CFD). The Reynolds-averaged Navier–Stokes (RANS) equations were solved to simulate regular waves in the absence of wind stress, and the resulting water velocities agreed with Stokes theory for waves. The RANS velocity field was then used to predict the transport of buoyant...

Solving Navier-Stokes equations using monotone algorithms often produces results that are consistent with the dynamics of high Reynolds number turbulence despite formally insufficient numerical resolution to capture all physically relevant scales of motion. It is frequently argued that the truncation error of a numerical scheme provides a mechanism for the energy dissipation and serves as an im...

Abstract Turbulence pervades most flows of engineering interest, and its prediction remains a challenge on both accuracy cost. One promising predictive approach that reduces cost combines large‐eddy simulation (LES) with based Reynolds averaged Navier–Stokes equations (RANS). This study presents method to overcome stability issues associated these hybrid LES‐RANS methods. The developed involves...

This paper focuses on a hydraulic radius separation approach used to calculate the boundary shear stress in terms of bed and wall shear stress proposed in a trapezoidal channel. The average bed and sidewall shear stress in smooth trapezoidal open channels are derived after using Guo & Julien (2005) early equations taking a part of an investigation to cover both rectangular and trapezoidal chann...

We are presenting the results of a stability analysis of a background wind shear in the presence of stablestratification and of height dependent coefficients of eddy viscosity and eddy thermal conduction. It is shownthat the vertical gradients of the eddy coefficients substantially affect the phase velocities, growth rates andvertical structure of the gravity wave and are respon...

The large-eddy simulation of the spatial evolution of a stationary cross ow vortex packet in a three-dimensional boundary layer was performed. Although a coarse grid was used (compared to that required by a direct numerical simulation) the essential features of the disturbance evolution, such as the spanwise disturbance spreading and the vortex rollover, were captured accurately. The eddy visco...

It is shown that a new mixed nonlinear/eddy viscosity LES model reproduces profiles better than a number of competing nonlinear and mixed models for plane channel flow. The objective is an LES method that produces a fully resolved turbulent boundary layer and could be applied to a variety of aerospace problems that are currently studied with RANS, RANS-LES, or DES methods that lack a true turbu...