CFD Simulation Method And Field Measurement Study Of Unban Rivers Effect On Thamal And Humidity Climate

With the development of the economy increasing urbanization in our country, people pay more attention on tropical island effect. Under the pressure of urban population, the natural underlaying surface such as rivers, green space is increasingly replaced by the artificial underlaying surface such as sand, concrete etc. The property of the artificial structures is low thermal capacitance and high roughness and etc. Under the same amount of solar radiation, the near-surface temperature in urban is warming faster and it is 2-10℃higher than the near-surface temperature in country.Urban rivers are the basic material conditions of the existence and development of an urban and an indispensable factor on purifing urban environment and being a part of urban landscape. Compared with general rivers, urban river has a lot of ecosystem functions such as purifing urban environment, maintaining ecological balance and etc., in addition to the unique connotation of cultural landscape. Because of the advantage of higher thermal capacitance and lower temperature and the wider space above river compared with other underlaying surface, the effect that urban river has on urban heat climate can not be ignored. Based on the status of rapid urbanization and social development, too much emphasising on economic development, ignoring the ecological and environmental protection in China, urban river faces serious problems, including the rapid decline of the area, artificializing, channelization and water pollution.According to the analysis metioned above, this paper discusses the effect that urban river has on urban heat climate using numerical simulation and field measurement methods. Firstly, a model is built on the condition of a commercial planning project. Secondly, Numerical simulation is undertaken with construction complex CFD three-dimensional computer program and the meteorological parameters. The CFD program includes the simplified calculation of the heat and mass transfer between the river and the surrounding communities and the influence of solar radiation. Finally, through the CFD simulation of urban river surrounding wind field and humidity field and temperature field, this paper analyzes and evaluates the effect that different water area size, the ground temperature and the dominant wind direction has on heat climate of the surrounding communities. Meanwhile, this paper measures the paremeters (temperature, humidity, etc.) of Songhua River in Harbin section and researches the regulatory role of rivers. The fixed and mobile measurement test points and test lines are determined and measured in outdoor environment according to previous technology. The distribution of wind velocity, wind direction and temperatrue on conditions of different underlaying surfaces on both sides of Songhua River has been gained according to the field measurement. This paper analyzes the fluctuation rule of temperature and concludes the influenced range that urban river has on urban heat climate in the actual situation in summer. Studies have shown that the main factors influencing thermal climate nearby rivers and thermal comfort is solar radiation, the river, as a cold source of urban, impacts slightly on temperature distribution nearby built-up areas. Air temperature increases progressively with the distance between nearby built-up areas and the bank, the degree of the influence is relevant to fluvial morphology, dominant wind direction and intensity of the related built-up areas.