The effects of a building＇s density on urban flows are investigated using a CFD model with the RNG k - ε turbulence closure scheme. Twenty-seven cases with different building＇s density parameters （e.g., building a...The effects of a building＇s density on urban flows are investigated using a CFD model with the RNG k - ε turbulence closure scheme. Twenty-seven cases with different building＇s density parameters （e.g., building and street-canyon aspect ratios） are numerically simulated. As the building＇s density parameters vary, different flow regimes appear. When the street canyon is relatively narrow and high, two counterrotating vortices in the vertical direction are generated. The wind speed along streets is mainly affected by the building＇s length. However, it is very difficult to find or generalize the characteristics of the street-canyon flows in terms of a single building＇s density parameter. This is because the complicated flow patterns appear due to the variation of the vortex structure and vortex number. Volume-averaged vorticity magnitude is a very good indicator to reflect the flow characteristics despite the strong dependency of flows on the variation of the building＇s density parameters. Multi-linear regression shows that the volume-averaged vorticity magnitude is a strong function of the building＇s length and the street-canyon width. The increase in the building＇s length decreases the vorticity of the street-canyon flow, while, the increase in the street- canyon width increases the vorticity.展开更多
The building parameters of Chinese solar greenhouse(CSG)directly affect the front roof lighting and indoor thermal environment.In order to obtain the optimal parameter combination,a building parameter optimization met...The building parameters of Chinese solar greenhouse(CSG)directly affect the front roof lighting and indoor thermal environment.In order to obtain the optimal parameter combination,a building parameter optimization method based on computational fluid dynamics(CFD)simulation and entropy weight method was proposed.Firstly,a three-dimensional thermal and humidity environment model of CSG was constructed considering the coupling effect of soil,crop,and back wall based on CFD.The reliability of the model was validated through experiments in a CSG of Yongqing County,Hebei Province of China.Then,the indoor air temperature rise rate,air temperature and humidity uneven coefficient,and average air temperature and humidity were selected as the evaluation indicators of CSG thermal and humidity environment.The ridge height,back wall height and the horizontal projection of back roof of CSG were selected as the three factors of the orthogonal test plan,and a three-factor and four-level plan was designed,resulting in 16 different parameter combinations.By use of CFD simulation,the thermal and humidity environment evaluation indicators under different parameter combinations were calculated.The entropy weight method was used to assign weights to the evaluation indicators,and the comprehensive evaluation indicators of CSG thermal and humidity environment were obtained based on the linear weighting principle.By comparing comprehensive evaluation indicators,the optimal combination of building parameters was obtained with a ridge height of 5.72 m,a back wall height of 3.2 m,and a horizontal projection of 2.1 m on the back roof.The research results can provide a practical and feasible method for optimizing the building parameters of CSG,and provided theoretical guidance for the structural design and optimization of CSG.展开更多
In order to quantitatively analyze the light radiation environment inside Chinese solar greenhouse (CSG) and select reasonable building design parameters, a CSG solar radiation environment model reflecting various fac...In order to quantitatively analyze the light radiation environment inside Chinese solar greenhouse (CSG) and select reasonable building design parameters, a CSG solar radiation environment model reflecting various factors such as geographical location, outside solar radiation, orientation and building parameters, front roof shape, and covering materials was studied. The model considered the impact of both cloudy and sunny weather conditions on the inside solar radiation environment, and established a simulation calculation method for inside direct radiation and scattered radiation. When calculating solar scattered radiation, the ground reflected radiation and atmospheric longwave radiation was considered. When calculating the transmittance of covering material, a structural shading loss and dust film model was introduced to calculate its impacts on the transmittance. The model was validated experimentally in a CSG at Yongqing in Hebei Province, China. The results showed that the model can effectively simulate the solar radiation of various points such as the ground and wall in the greenhouse at any time, with an average relative error of 8.19% between the simulated and measured values. Based on the established model, the impact of the geographical location, azimuth angle, and building parameters of CSG on inside solar radiation were analyzed. The research results can provide theoretical references and relevant data for the wall and soil heat storage, crop planting, and energy balance of enclosure structures in CSG.展开更多
基金funded by the Korea Meteorological Administration Research and Development Program under Grant CATER 2007–3307
文摘The effects of a building＇s density on urban flows are investigated using a CFD model with the RNG k - ε turbulence closure scheme. Twenty-seven cases with different building＇s density parameters （e.g., building and street-canyon aspect ratios） are numerically simulated. As the building＇s density parameters vary, different flow regimes appear. When the street canyon is relatively narrow and high, two counterrotating vortices in the vertical direction are generated. The wind speed along streets is mainly affected by the building＇s length. However, it is very difficult to find or generalize the characteristics of the street-canyon flows in terms of a single building＇s density parameter. This is because the complicated flow patterns appear due to the variation of the vortex structure and vortex number. Volume-averaged vorticity magnitude is a very good indicator to reflect the flow characteristics despite the strong dependency of flows on the variation of the building＇s density parameters. Multi-linear regression shows that the volume-averaged vorticity magnitude is a strong function of the building＇s length and the street-canyon width. The increase in the building＇s length decreases the vorticity of the street-canyon flow, while, the increase in the street- canyon width increases the vorticity.
基金support provided by Hebei Province Key Research and Development Program (Grant No.22327214D)Independent Research and Development Plan of Academy of Agricultural Planning and Engineering,Ministry of Agriculture and Rural Affairs (Grant No.SP202101).
文摘The building parameters of Chinese solar greenhouse(CSG)directly affect the front roof lighting and indoor thermal environment.In order to obtain the optimal parameter combination,a building parameter optimization method based on computational fluid dynamics(CFD)simulation and entropy weight method was proposed.Firstly,a three-dimensional thermal and humidity environment model of CSG was constructed considering the coupling effect of soil,crop,and back wall based on CFD.The reliability of the model was validated through experiments in a CSG of Yongqing County,Hebei Province of China.Then,the indoor air temperature rise rate,air temperature and humidity uneven coefficient,and average air temperature and humidity were selected as the evaluation indicators of CSG thermal and humidity environment.The ridge height,back wall height and the horizontal projection of back roof of CSG were selected as the three factors of the orthogonal test plan,and a three-factor and four-level plan was designed,resulting in 16 different parameter combinations.By use of CFD simulation,the thermal and humidity environment evaluation indicators under different parameter combinations were calculated.The entropy weight method was used to assign weights to the evaluation indicators,and the comprehensive evaluation indicators of CSG thermal and humidity environment were obtained based on the linear weighting principle.By comparing comprehensive evaluation indicators,the optimal combination of building parameters was obtained with a ridge height of 5.72 m,a back wall height of 3.2 m,and a horizontal projection of 2.1 m on the back roof.The research results can provide a practical and feasible method for optimizing the building parameters of CSG,and provided theoretical guidance for the structural design and optimization of CSG.
基金support provided by Agricultural Planning Talent Project of Academy of Agricultural Planning and Engineering,MARA(Grant No.QNYC-2024-10)Independent Research and Development Plan of Academy of Agricultural Planning and Engineering,MARA(Grant No.SH202402 and Grant No.SP202101)+1 种基金National Natural Science Foundation of China(Grant No.32201657)Shandong Natural Science Foundation Project(Grant No.ZR2021QF091).
文摘In order to quantitatively analyze the light radiation environment inside Chinese solar greenhouse (CSG) and select reasonable building design parameters, a CSG solar radiation environment model reflecting various factors such as geographical location, outside solar radiation, orientation and building parameters, front roof shape, and covering materials was studied. The model considered the impact of both cloudy and sunny weather conditions on the inside solar radiation environment, and established a simulation calculation method for inside direct radiation and scattered radiation. When calculating solar scattered radiation, the ground reflected radiation and atmospheric longwave radiation was considered. When calculating the transmittance of covering material, a structural shading loss and dust film model was introduced to calculate its impacts on the transmittance. The model was validated experimentally in a CSG at Yongqing in Hebei Province, China. The results showed that the model can effectively simulate the solar radiation of various points such as the ground and wall in the greenhouse at any time, with an average relative error of 8.19% between the simulated and measured values. Based on the established model, the impact of the geographical location, azimuth angle, and building parameters of CSG on inside solar radiation were analyzed. The research results can provide theoretical references and relevant data for the wall and soil heat storage, crop planting, and energy balance of enclosure structures in CSG.
