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
R-function is a widely used tool when considering objects obtained through the Boolean operations start from simple base primitives.However,there is square root operation in the representation.Considering that the use...R-function is a widely used tool when considering objects obtained through the Boolean operations start from simple base primitives.However,there is square root operation in the representation.Considering that the use of splines will facilitate the calculations within the CAD system,in this paper,we propose a system of R-functions represented in spline form called Spline R-function(SR).After trans-forming the function ranges of two base primitives to a new coordinate system,a series of sign constraints following a specific Boolean operation are derived and the spline R-function can be formulated as a piecewise function.Representation of SR in both B´ezier form and B-spline form have been given.Among which the B´ezier ordinates are determined with the help of the B-net method through setting up a series of relations according to the sign constraints and properties of R-functions.The construction processes for both Boolean intersection and union operations with different smoothness are discussed in detail.Numerical experiments are conducted to show the potential of the proposed spline R-function.展开更多
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.
文摘当前国内外对胶凝砂砾石大坝(CSG Dam)渗流场的研究均局限于稳定渗流场,但由于库水位的不断波动,大坝在运行期大都处于非稳定渗流状态,保证这种新型坝在库水位变化时的安全稳定非常重要。采用有限体积法及计算流体力学中的VOF(volume of fluid, VOF)法,对CSG坝两个极端工况下的非稳定渗流场进行模拟,获得孔隙水压力、浸润面、流速及流量的演变过程,结果表明:1)CSG坝体防渗效果良好,即使在面板防渗性能降低的情况下,浸润线也处于较低的高程;2)在水位上升阶段,坝踵附近在水位上升初期渗流量会出现不稳定波动,下游节点渗流量变化起步较晚,且需要经历一个较长的时间才能达到渗流稳定;3)水位下降时,坝体浸润面呈现中间高、两边低,上游高、下游低的趋势。一部分坝内渗水会向上游排出,产生的渗透压力不利于面板的稳定,建议在坝趾处采取排水措施,引导坝内渗水排出,减少对上游面板的不利影响。
基金We would like to thank the anonymous reviewers and our labo-ratory group for helpful discussions and comments.The work is supported by the NSF of China(No.11771420).
文摘R-function is a widely used tool when considering objects obtained through the Boolean operations start from simple base primitives.However,there is square root operation in the representation.Considering that the use of splines will facilitate the calculations within the CAD system,in this paper,we propose a system of R-functions represented in spline form called Spline R-function(SR).After trans-forming the function ranges of two base primitives to a new coordinate system,a series of sign constraints following a specific Boolean operation are derived and the spline R-function can be formulated as a piecewise function.Representation of SR in both B´ezier form and B-spline form have been given.Among which the B´ezier ordinates are determined with the help of the B-net method through setting up a series of relations according to the sign constraints and properties of R-functions.The construction processes for both Boolean intersection and union operations with different smoothness are discussed in detail.Numerical experiments are conducted to show the potential of the proposed spline R-function.
