Numerical Analysis of Low-Prandtl Jets in Turbulent Forced Convection Regimes

The current need to ensure an effective and prompt transition of the energy sector towards zero-carbon has renewed the interest for nuclear technology. Small Modular Reactors (SMRs) seem particularly interesting for their reduced capital cost, operational flexibility and enhanced safety and security. Different SMR concepts are being developed...

Combined Large-Eddy and Direct Numerical Simulations of a Planar Jet with Heated Co-Flow with Medium and Low Prandtl Fluids

In the present work, we have applied a combined dynamic large-eddy simulation (LES) and direct numerical simulation (DNS) approach for a three-dimensional planar jet in a turbulent forced convection regime (Re = 18000) with a heated co-flow. Results from LES are compared with Reynolds Averaged Navier-Stokes (RANS) simulations and experimental...

Numerical and experimental analysis of a planar jet with heated co-flow at medium and low Prandtl-number values

In the present work, we combine experiments and numerical simulations of a planar jet with heated co-flow with medium (air) and low-Prandtl (He-Xe gas mixture) fluids. Jets are recognized as representative test cases to be investigated in large components of pool-type liquid metal-cooled nuclear systems, like the Multi-purpose hYbrid Research...

Addressing the Grid-Size Sensitivity Issue in Large-Eddy Simulations of Stable Boundary Layers

We have identified certain fundamental limitations of a mixing-length parametrization used in a popular turbulent kinetic energy-based subgrid-scale model. Replacing this parametrization with a more physically realistic one significantly improves the overall quality of the large-eddy simulation (LES) of stable boundary layers. For the range...

On sedimentation processes in a stratified estuarine system

On total turbulent energy and the passive and active role of buoyancy in turbulent momentum and mass transfer

A steady solution for Prandtl’s self-similar vortex sheet spirals

Prandtl's [L. Prandtl, Über die Entstehung von Wirbeln in der idealen Flüssigkeit, mit Anwendung auf die Tragflügeltheorie und andere Aufgaben, in: von Kármán, Levi-Cevita (Eds.), Vorträge aus dem Gebiete der Hydro- und Aerodynamik, Springer, Berlin, 1922] self-similar, semi-infinite, free vortex sheets are characterized by a two-dimensional...

Entraining Flow of a Concentrated Benthic Suspension: Computations with the Prandtl Mixing-Length Model

The Prandtl mixing-length model of turbulent exchange of mass and momentum is applied to calculate the entrainment of overlying water into a layer of suspended fine sediment at a horizontal bed. In the field the flow and turbulence in such a concentrated benthic suspension (CBS) are driven by a streamwise pressure gradient resulting from the...

Laminarisation in Flows of Concentrated Benthic Suspensions: Computations with a Low-Re Mixing-Length Model

In quiescent water bodies that form part of estuarine or coastal water systems, such as harbours and access channels, fine sediments may deposit to form concentrated benthic suspensions (CBS). The flow velocities in these mud layers may become low, and the viscosities may become large, so that the Reynolds number decreases below a critical value...

Saturation Concentrations of Suspended Fine Sediment: Computations with the Prandtl Mixing-Length Model

Adopting a 1DV numerical model including the standard k-eps turbulence model, Winterwerp et al. (1999) calculated a saturation concentration for an initially uniform distribution of fine sediment concentration in steady flow. At concentrations exceeding the saturation concentration the concentration profile collapsed and all sediment was...

An asymptotic solution for slightly buoyant laminar plumes