It is well known that the addition of small amounts of long chain polymers produces dramatic effects on flowing fluids. A remarkable effect, recently observed experimentally, is the onset of ”elastic turbulence” in the limit of very low Reynolds number Re, provided elasticity is high enough [1]. In this regime, the polymer solution displays features typical of turbulent flows. Consequently, ela...

The design of a new, truly robust multigrid framework for the solution of steady-state Reynolds-averaged Navier-Stokes (RANS) equations with two-equation turbulence models is presented. While the mean-flow equations and the turbulence model equations are advanced in time in a loosely-coupled manner, their multigrid cycling is strongly coupled (FC-MG). Thanks to the loosely-coupled approach, the...

Optimal control of enclosed environment requires detailed information of air distribution that could be obtained by numerically solving Navier-Stokes equations with a suitable turbulence model. This investigation evaluated the performance of eight turbulence models for transient airflow in enclosed environment using experimental data obtained in a room. The study used the room to create three c...

[1] The Mellor‐Yamada turbulence closure scheme, used in many ocean circulation models, is often blamed for overly high simulated surface temperature and overly low simulated subsurface temperature in summer due to insufficient vertical mixing. Surface waves can enhance turbulence kinetic energy and mixing of the upper ocean via wave breaking and nonbreaking‐wave‐turbulence interaction. The inf...

A class of subgrid stress ~SGS! models for large-eddy simulation ~LES! is presented based on the idea of structure-based Reynolds-stress closure. The subgrid structure of the turbulence is assumed to consist of stretched vortices whose orientations are determined by the resolved velocity field. An equation which relates the subgrid stress to the structure orientation and the subgrid kinetic ene...

This paper summarises some of the recent progress that has been made in understanding astrophysical plasma turbulence in the solar wind, from in situ spacecraft observations. At large scales, where the turbulence is predominantly Alfvénic, measurements of critical balance, residual energy and three-dimensional structure are discussed, along with comparison to recent models of strong Alfvénic tu...

In my thesis I study two different models of turbulence. The first part of my research concerns the, so-called, shell models of turbulence. Shell models had attracted a lot of interest as useful phenomenological models that mimics certain features of the Navier-Stokes equations (NSE). The shell models capture different aspects of the real turbulent flows, such as the energy cascade, an anomalou...

The turbulent flow in a tangential inlet / tangential outlet vortex tube is numerically simulated using a modified   k turbulence model. The results are compared to experimental measurements from literature. The modified model shows better agreement with the local tangential velocity measurements compared to the standard and RNG   k turbulence models. The flow structure is also demonstrated...

Atmospheric turbulence has significant influences on both the trajectories and strengths of wake vortices. In this paper, a quasi-wavelet method is used to generate a random atmospheric turbulence field based on the von Kármán spectrum, in which atmospheric turbulence is represented by groups of random eddies. An inviscid wake vortex system, out-of-ground effect or in-ground effect, is immersed...

As part of a more general program of developing multiple-scale models of turbulence, Schiestel suggested a derivation of the homogeneous part of the dissipation rate transport equation. Schiestel's approach is generalized to rotating turbulence. The resulting model reproduces the main features observed in decaying rotating turbulence.