Large Eddy Simulation (LES) undeniably has the potential to provide more accurate and more reliable results than simulations based on the Reynolds-averaged Navier-Stokes (RANS) approach. However, LES entails a higher simulation complexity and a much higher computational cost. In spite of some claims made in the past decades that LES would render RANS obsolete, RANS remains widely used in both research and engineering practice. This paper attempts to answer the questions why this is the case and whether this is justified, from the viewpoint of building simulation, both for outdoor and indoor applications. First, the governing equations and a brief overview of the history of LES and RANS are presented. Next, relevant highlights from some previous position papers on LES versus RANS are provided. Given their importance, the availability or unavailability of best practice guidelines is outlined. Subsequently, why RANS is still frequently used and whether this is justified or not is illustrated by examples for five application areas in building simulation: pedestrian-level wind comfort, near-field pollutant dispersion, urban thermal environment, natural ventilation of buildings and indoor airflow. It is shown that the answers vary depending on the application area but also depending on other—less obvious—parameters such as the building configuration under study. Finally, a discussion and conclusions including perspectives on the future of LES and RANS in building simulation are provided.

/pdf/les-over-rans-in-building-simulation-for-outdoor-and-indoor-1zmy3qiwyr.pdf

LES over RANS in building simulation for outdoor and indoor applications: A foregone conclusion?

Enhancing urban ventilation performance through the development of precinct ventilation zones: A case study based on the Greater Sydney, Australia

Characterization of aerodynamic performance of vertical axis wind turbines : impact of operational parameters

Influence of urban morphological characteristics on thermal environment

CFD simulation of urban microclimate: Validation using high-resolution field measurements.

https://pure.tue.nl/ws/files/80916680/1_s2.0_S0360132317304687_main.pdf

CFD and wind-tunnel analysis of outdoor ventilation in a real compact heterogeneous urban area: Evaluation using “air delay”

Research attempts on biomass use constitute a response to the growing demand for sustainable and low-cost energy from renewable sources. Hence, the sustainable use of Posidonia oceanica (PO) waste as a material for biomass to produce green energy is being considered in many countries in the Mediterranean region. PO meadows are considered as the main type of sea flora in the Greek coasts. PO can extract biomass from nearby ecosystems of the coastal zone, either directly through the transportation of disposed non-living leaves or indirectly via benthic organisms. The aim of this study is to investigate the use of PO waste derived from Kefalonia Island (Greece) as a biomass source. PO samples were collected around the island, and they were mineralogically and microstructurally analyzed. In addition, physicochemical, chemical, and thermogenic tests were performed in order to obtain the optimum and most completed characterization of the material. Based on the results, cellulose seems to be the main structural component of PO, which also seems to determine their behavior. PO presents microscopic similarities to other lignocellulosic materials which composition is made of carbonates, lignin, extractives, and minerals. Ash and moisture content constitute the two critical parameters that are responsible for the energy differences of each biomass. The outcome of this study shows the potential use of PO wastes as an interesting source for energy production.

/pdf/posidonia-oceanica-balls-egagropili-from-kefalonia-island-2p70vr3a.pdf

Posidonia oceanica Balls (Egagropili) from Kefalonia Island Evaluated as Alternative Biomass Source for Green Energy

Considering the radical increase of urban population and the trend toward urbanization, the analysis of microclimatic conditions in the urban environment is getting more significant. In this perspective, this study analyzes microclimatic conditions in a real urban area. The real compact inhomogeneous urban area under study is located in Nicosia old town, in Cyprus. High-resolution Computational Fluid Dynamics (CFD) simulations are performed based on the 3D unsteady Reynolds-Averaged Navier-Stokes equations to assess the air temperature and wind speed distributions. The CFD results are compared with on-site measurements for the same area. The results show that CFD can predict air temperatures in compact real urban areas, with an average deviation of 6.8%. Based on the results, conclusions are going to be made regarding thermal comfort in the case study area.

N Nestoras Antoniou

Papers

CFD and wind-tunnel analysis of outdoor ventilation in a real compact heterogeneous urban area: Evaluation using “air delay”

CFD simulation of urban microclimate: Validation using high-resolution field measurements.

Posidonia oceanica Balls (Egagropili) from Kefalonia Island Evaluated as Alternative Biomass Source for Green Energy

CFD simulations and field measurements of urban microclimate in a real compact heterogeneous urban area