Study On The Thermal Environment Of Sunken Plaza Of Commercial Building In Hot And Humid Regions

The development and utilization of urban underground space and the rise of public space in commercial buildings has promoted the application of sunken plazas in commercial buildings.The sunken plaza in commercial buildings effectively utilizes the urban underground space and plays the role of a node linking the surrounding space,which is conducive to the integration design of buildings,underground transportation and underground commerce.As the place for outdoor activities of commercial building,it faces thermal comfort problems caused by high temperature and radiation,especially in hot and humid areas,creating a comfortable physical environment can improve people’s shopping experience and can provide commercial buildings with additional economic benefits.However,there is a lack of research on the microclimate of sunken plazas in commercial buildings.The aim of this paper is to investigate the characteristics of the wind and thermal environments of sunken plazas in commercial buildings,to study the simulation methods for the wind and thermal environments of sunken open spaces,and to assess the role of different morphological factors on the wind and thermal environments of sunken plazas.Through the case study,we summarize the morphological characteristics of the sunken plaza of commercial buildings and classify them into four categories: independent,entrance,street and atrium types according to the enclosing relationship between commercial buildings and the sunken plaza,and establish simplified models.Through on-site measurements,the environmental characteristics of the sunken plaza of commercial buildings are analyzed,and the differences of meteorological parameters between different measurement points of the sunken plaza and its surrounding environment are compared.The results show that: on sunny days,the blockage of solar radiation is the main reason for the temperature difference between measurement points,and the temperature and wind speed fluctuations of the ground entrance are greater than those of the underground measurement points;on cloudy days with weak radiation,the temperature difference between measurement points of the sunken plaza is smaller,and the wind speed may be the main reason for the the temperature difference.The simulation accuracy of OpenFOAM software is verified,and the simulation method of numerical wind tunnel bottom boundary consisting of sunken plaza ground,sunken plaza wall and building ground together is established.Based on the CTTC model and its theory,the CTTC model calculation formula that considers the solar radiation of the wall and is weighted by area is selected,the CTTC model is validated,and the solar radiation and the average sky view factor at the pedestrian height are calculated by Ladybug to establish the thermal environment simulation method.Taking Guangzhou,a representative city in humid and hot areas,as an example,the simulation results show that the average wind speed at the pedestrian height of the sunken plaza is below 1m/s for most conditions;the average wind speed of the independent sunken plaza is influenced by the depth to width ratio of the plaza;the acceleration at the corner of the building can increase the average wind speed of the entrance type sunken plaza;the opening of the the building walls does not necessarily improve the wind environment at the pedestrian height of the sunken plaza.The air temperature of the independent sunken plaza decreases with the increase of sinking depth,and the average air temperature is the lowest when the entrance type sunken plaza is located in the west side of the complex,and the street type sunken plaza with north-south orientation has the lowest air temperature and receives the least solar radiation on the ground,and the air temperature of the internal pedestrian space of the atrium type does not differ greatly under different cases.