A new B-spline surface reconstruction method from layer data based on deformable model is presented. An initial deformable surface, which is represented as a closed cylinder, is firstly given. The surface is subject t...A new B-spline surface reconstruction method from layer data based on deformable model is presented. An initial deformable surface, which is represented as a closed cylinder, is firstly given. The surface is subject to internal forces describing its implicit smoothness property and external forces attracting it toward the layer data points. And then finite element method is adopted to solve its energy minimization problem, which results a bicubic closed B-spline surface with C^2 continuity. The proposed method can provide a smoothness and accurate surface model directly from the layer data, without the need to fit cross-sectional curves and make them compatible. The feasibility of the proposed method is verified by the experimental results.展开更多
Taking advantage of the relation of lateral Lagrangian time scale T_(LY) with the stability and height, we establish a three-dimensional random dispersion model and simulate the dispersing process of a ground source w...Taking advantage of the relation of lateral Lagrangian time scale T_(LY) with the stability and height, we establish a three-dimensional random dispersion model and simulate the dispersing process of a ground source within the surface layer. The results calculated show that under the condition of stable stratifica- tion our model is obviously better improved than those obtained by assuming T_(LY) to be constant, while under unstable condition, not much improved.展开更多
A modification of the Monin-Obukhov theory is proposed,introducing a two-layer model of the convective atmospheric surface layer(ASL)with a fixed interlayer boundary.The convective ASL is assumed to consist of a frict...A modification of the Monin-Obukhov theory is proposed,introducing a two-layer model of the convective atmospheric surface layer(ASL)with a fixed interlayer boundary.The convective ASL is assumed to consist of a frictional-heat sublayer,adjacent to the underlying surface,and a forced-convection sublayer.Approximations of the turbulent moments are derived independently for each sublayer in the form of truncated Taylor expansions in the modified dimensionless height.The interlayer boundary is fixed and defined on the basis of the bifurcation hypothesis.This hypothesis postulates the existence within the ASL of a domain of strong turbulence,represented by a coherent structure formed by an ensemble of small convective eddies(thermals),and a domain of weak turbulence,represented by eddy-wave motion.According to the bifurcation hypothesis,the strong-turbulence domain corresponds to the forcedconvection sublayer,whereas the weak-turbulence domain corresponds to the frictional-heat sublayer.The proposed approach makes it possible to construct a one-parameter family of approximations for a wide class of turbulent moments.The one-parameter model,validated against available experimental data,shows that the proposed piecewiselinear approximation is accurate across the entire convective ASL and demonstrates a high degree of universality.展开更多
基金This project is supported by National Natural Science Foundation of China(No. 10272033) and Provincial Natural Science Foundation of Guangdong,China(No.04105385).
文摘A new B-spline surface reconstruction method from layer data based on deformable model is presented. An initial deformable surface, which is represented as a closed cylinder, is firstly given. The surface is subject to internal forces describing its implicit smoothness property and external forces attracting it toward the layer data points. And then finite element method is adopted to solve its energy minimization problem, which results a bicubic closed B-spline surface with C^2 continuity. The proposed method can provide a smoothness and accurate surface model directly from the layer data, without the need to fit cross-sectional curves and make them compatible. The feasibility of the proposed method is verified by the experimental results.
文摘Taking advantage of the relation of lateral Lagrangian time scale T_(LY) with the stability and height, we establish a three-dimensional random dispersion model and simulate the dispersing process of a ground source within the surface layer. The results calculated show that under the condition of stable stratifica- tion our model is obviously better improved than those obtained by assuming T_(LY) to be constant, while under unstable condition, not much improved.
基金carried out by Vulfson A.N.within the framework of the Governmental Order to the Water Problems Institute,Russian Academy of Sciences,research project No.FMWZ-2022-0001。
文摘A modification of the Monin-Obukhov theory is proposed,introducing a two-layer model of the convective atmospheric surface layer(ASL)with a fixed interlayer boundary.The convective ASL is assumed to consist of a frictional-heat sublayer,adjacent to the underlying surface,and a forced-convection sublayer.Approximations of the turbulent moments are derived independently for each sublayer in the form of truncated Taylor expansions in the modified dimensionless height.The interlayer boundary is fixed and defined on the basis of the bifurcation hypothesis.This hypothesis postulates the existence within the ASL of a domain of strong turbulence,represented by a coherent structure formed by an ensemble of small convective eddies(thermals),and a domain of weak turbulence,represented by eddy-wave motion.According to the bifurcation hypothesis,the strong-turbulence domain corresponds to the forcedconvection sublayer,whereas the weak-turbulence domain corresponds to the frictional-heat sublayer.The proposed approach makes it possible to construct a one-parameter family of approximations for a wide class of turbulent moments.The one-parameter model,validated against available experimental data,shows that the proposed piecewiselinear approximation is accurate across the entire convective ASL and demonstrates a high degree of universality.
