High Resolution LES of Turbulent Flow in the Vicinity of Buildings including Thermal Effects
Responsible: Marcus Oliver Letzel
Project type: individual ​DFG research projects & PhD scholarship of the ​German National Academic Foundation (Studienstiftung des deutschen Volkes)
Duration: 01/01/2003 - 31/12/2006
The goal of this project is to look into the detailed structure of building-induced turbulence and how it is affected by thermal stratification.

The parallel cluster architecture of the new Hochleistungsrechenzentrum Nord (​HLRN) now principally allows to simultaneously run two coupled or nested model sets on different computer clusters ('grid computing'). This new feature will be applied to PALM within the scope of this project with the aim to extend the scale range of turbulent flow around buildings that is resolvable by LES models by at least an order of magnitude compared with usual models. This yields new prospects for model validation and the development and testing of turbulence parameterizations, especially under convective conditions (unstable thermal stratification).

Physical analysis will commence with flow around a single cubic obstacle, followed by street canyon flow, for neutral and convective boundary layers. The results will be used to e.g.

• validate PALM against laboratory (wind tunnel) experiments,
• analyze differences between high resolution LES and former LES with lower resolution, and
• evaluate turbulence parameterizations employed in lower resolution models.
  
  

Modelling aspects of this project involve PALM code implementations such as turbulent inflow and noncyclic boundary conditions, horizontal grid stretching or grid nesting (see also the studies by Gryschka and Steinfeld), a dynamic subgrid scale model, thermal building wall boundary conditions, and suitable visualization methods.