A Numerical Model for the Study of Thermal Effect of Grass-Covered Parks in a Humid Urban Area

Abstract

Abstract A numerical simulation is carried out to analyze the tempera-ture change of an urban green area for different times of day for a meteorologically calm condition in summer. Several parameters contribute to changes of the surface layer, e.g., irrigation, plants height, water bodies, etc. Grassland cooling effect can lead to sub-stantial decrease of energy consumption, especially in urban areas in warm seasons, for air-conditioning. In this study a numerical model for the simulation of the temperature and humidity changes of an urban grass-covered park was developed. Also the main object in this study was to determine the effect of soil and grass leaf humidity of an urban park with grass cover on air temperature in a humid city in summer. In this approach, air flow over grass was simulated using solutions of two dimensional Reynolds Aver-aged Navier-Stokes (RANS) equations and a standard k -e model for turbulence. Also heat and humidity equations with RANS equations were solved using the SIMPLE algorithm with a finite difference method. For the air surface interaction, the Deardorff Soil–Vegetation–Atmosphere Transfer (SVAT) model was used to estimate the evaporation-evaportranspiration of grass which has a key role in controlling the temperature and humidity of air over grass. For a more realistic numerical simulation, instead of well mixed air assumption for the inlet flow, a wind logarithmic profile based on stability conditions of air at the inlet of the computation-al domain was utilized. The model results, with conditions of an urban grass-covered park in Nagoya, Japan, show similar trends with observation; hence it seems that such model may be used for the study of air temperature and humidity variations, while using an irrigation program over grass, during the diurnal cycle in urban areas.