Study Of The Effect Of Urban Water Body On The Adjacent Local Thermal Environment

As one of the complex underlying surfaces, the urban waterfront areas often become the most attractive site, due to its variety water scene. At the same time, the rivers, lakes and artificial water body not only realized their ecological functions but also improved the local thermal climate in the surrounding area of the waterfront. Therefore, this paper, taking the water effect and factor analysis as the research object, combining the theoretical analysis, field measurement and numerical simulation research methods to study the diffusion mechanism and longterm dynamic law of flux transfer between water body and the atmospheric. Meanwhile, we systematic researched dynamic climate effect under different conditions and analysis the impact of the thermal environment factors on the climatic effect characteristics of the water body.This study adopts the method of theory analysis to study the climate effect of the water body using two-dimensional steady-state finite model. The model considered the influence of vertical embankment. The results showed that increase of embankment height and the wind flow profile index can largely weaken the spread scale of climatic effect of the water body.Taking the site on the simple and uniform suburban waterfront in Hulan River in Harbin as observation object, this research used reliable advanced eddy covariance system to study the turbulence and flux transfer characteristics for a long time. After filtering and gap filling, we primarily analyzed the local climate characteristics around the river, the turbulence characteristics, flux transfer characteristics and regularity of the correlation coefficient. Results showed that the various characteristic parameters of local climate have obvious differences between day and night with the seasonal changes. The flux transfer intensity between the river and atmosphere is highly related to the atmospheric stability.Taking Harbin segment of Songhua River as the observation object, we used the statistical and modeling method to analyze the local climate located in the city centre with relatively high human activity dense. The regression method and the stochastic model were used to analyze the internal correlation bwtween river surface temperature and air temperature in the whole year. The simple temperature prediction model is obtained. At the same time, combining with the results of Hulan River, we validated the heat transfer model and found that the river temperature and air temperature in the urban is higher than that in the suburb due to the the influence of human activity. The latent heat between the river and the atmosphere in the urban were more significant and worked as a dominate factors in the variation of humidity of the thermal environment near the river.We built and validated local thermal environment CFD model around the water body, concluding the characteristics of common underlying surfaces such as water body and trees. By comparing the performances in predicting the humidity environment of different turbulence models, the RNG k-ε turbulent model was deemed to have the best performance on predicting thermal and humidity environment in the uraben waterfront areas.Based on the above CFD method, we analyzed the key factors which influencing thermal and humidity environment in the waterfront areas. The results indicated that the influence scales of thermal and humidity environment were highly dependent on the geometry of ventilation gallery in the residential areas of the waterfront. Combined with the evaluation index in this paper, the effects of the notable factors on average humidy, temperature and WBGT were mainly discussed in the residential areas. The results showed that the plot ratio and the embankment height had the most obvious effect on water vapor dispersion. The air liquidity in the plane-type and dot-plane-type distribution were much better which was beneficial to the humidity effect of waterbody on the local thermal environment. Meanwhile, the results also indicated that the temperature in area with the low plot ratio and large ventilation gallery was more easily affected by the waterbody.As a consequence of the above, the paper analyzed the dispersion mechanism and trend of thermal and humidity parameters using theoretical analysis, field measurement and numerical simulation, discussed the influence of water body on the thermal environment at the residential areas in urban waterfront areas based on local thermal environment CFD model. The conclusion in the paper could not only be taken as the fundamental data of researches in the future, but also is a planning guidance of outdoor environment in the urban waterfront areas.