Recently, monolithic and closed sports stadiums with big stands and large roofs have attracted attention as they contribute to increasing the number of attendance and availability ratio of a stadium. Closure of stadiums causes a decrease in the wind velocity and the volume of ventilated air on the turf pitch.
However, the environment suitable for a desirable growth of the natural grass of the turf requires good ventilation. In particular, the quality of the natural grass can be deteriorated during summer season, when the wind velocity and the volume of ventilated air are decreased. The reason for this has been attributed to an increase in the turf surface temperature as a result of the shortage of heat release from grass and soil by evaporation. As a countermeasure, large-size ventilation fans have been increasingly used in sports stadiums.
Therefore, to maintain a high-quality turf pitch for players and spectators, and to realize easy maintenance and management, it is important to design the configuration of sports stadiums with a consideration for natural ventilation. In addition, to save the energy consumption of ventilation fans in existing stadiums, it is necessary to derive an appropriate layout and blowing direction of fans according to the characteristics of the natural ventilation of each stadium.
Therefore, the authors have developed a coupling analysis based on an iterative partitioned method for turf thermal environment analysis. This analysis carries out the coupled simulation of radiation, convection, moisture transport, and heat budget of the turf surface for the prediction of the thermal environment near the turf surface and the condition of turf surface. This paper describes the outline of the method and the simulation results under natural ventilation with additional large mechanical fans in a stadium.
First, the configuration of the stadium is reproduced in three dimensions. The turf surface temperature around the low wind velocity area is increased. This temperature distribution can accurately reproduce the measured results. Moreover, heat release by latent heat of evaporation from the turf surface is shown to be about 8 to 10 times larger than other heat flux components. Therefore, it is important, in order to reduce the turf surface temperature, to promote latent heat of evaporation by increasing the amount of moisture transport from the turf to the air through air flow generation and discharging highly humid air form turf pitch by ventilation.
Next, the effects of the ventilation fan with a swinging function on decreasing the turf surface temperature are simulated under the calm wind condition based on unsteady simulation. The iterative partitioned method enables the unsteady coupled simulation of radiation, convection, moisture transport, and heat budget of the turf surface. A ventilation fan can generate airflow and reduce turf surface temperature in a wide range of about half of the grass pitch by its swinging motion. However, in half of the downwind of the grass pitch, although wind velocity remained, the turf surface temperature increased owing to moisture retention. This result indicates that layout and blowing direction planning of ventilation fans considering the quick discharge of highly humid air is important.
In conclusion, the coupled analysis of radiation, convection, and humidity based on separation-iterative solution method is effective for the planning of natural ventilation and the operation of the large fan for stadiums with consideration of the quality of natural grass of the turf pitch.
