Simulation of urban wind environments is essential for urban planning,pollution mitigation,and renewable energy applications.However,the high computational cost of high-fidelity computational fluid dynamics(CFD)method...Simulation of urban wind environments is essential for urban planning,pollution mitigation,and renewable energy applications.However,the high computational cost of high-fidelity computational fluid dynamics(CFD)methods limits their practical deployment in real urban contexts.To overcome this challenge,we propose a Fourier Neural Operator(FNO)model for predicting urban wind fields across different wind directions and city layouts,trained on velocity data generated by large-eddy simulations(LES)with the CityFFD solver.The results demonstrate that the FNO achieves accuracy comparable to CFD while reducing the per-frame wall-clock time from 2.210 s with CityFFD to 0.006 s on an NVIDIA V100 GPU,corresponding to an approximately 370x speedup.To further mitigate GPU memory constraints,a patch-based training strategy is introduced,which partitions the wind field into smaller spatial blocks,enabling the FNO to capture localized flow dynamics more effectively.In addition,incorporating signed distance function(SDF)data provides critical building-geometry information,thereby improving boundary recognition,enhancing prediction realism,and strengthening overall model generalizability.展开更多
The simulation of rarefied gasflows through complex porous media is chal-lenging due to the tortuousflow pathways inherent to such structures.The Lattice Boltzmann method(LBM)has been identified as a promising avenue ...The simulation of rarefied gasflows through complex porous media is chal-lenging due to the tortuousflow pathways inherent to such structures.The Lattice Boltzmann method(LBM)has been identified as a promising avenue to solveflows through complex geometries due to the simplicity of its scheme and its high parallel computational efficiency.It has been proposed to model the stress-strain relationship with the extended Navier-Stokes equations rather than attempting to directly solve the Boltzmann equation.However,a regularization technique is required tofilter out non-resolved higher-order components with a low-order velocity scheme.Although slip boundary conditions(BCs)have been proposed for the non-regularized multiple relaxation time LBM(MRT-LBM)for planar geometries,previous slip BCs have never been verified extensively with the regularization technique.In this work,following an extensive literature review on the imposition of slip BCs for rarefiedflows with the LBM,it is proven that earlier values for kinetic parameters developed to impose slip BCs are inaccurate for the regularized MRT-LBM and differ between the D2Q9 and D3Q15 schemes.The error was eliminated for planarflows and good agreement be-tween analytical solutions for arrays of cylinders and spheres was found with a wide range of Knudsen numbers.展开更多
基金upport from the Consortium for Research and Innovation in Aerospace in Québec(CRIAQ)through the project“Multi-scale Aerodynamic Modeling of Helicopters/UAV in Urban Environments”[#051811]the Natural Sciences and Engineering Research Council(NSERC)of Canada through the Discovery Grants Program[#RGPIN-2024-06297]the SEED project Creating Electrified and Decarbonized Healthy Urban Microclimate around Building Clusters through Climate-Resilient Solutions under the Canada First Research Excellence Fund(Volt-Age).
文摘Simulation of urban wind environments is essential for urban planning,pollution mitigation,and renewable energy applications.However,the high computational cost of high-fidelity computational fluid dynamics(CFD)methods limits their practical deployment in real urban contexts.To overcome this challenge,we propose a Fourier Neural Operator(FNO)model for predicting urban wind fields across different wind directions and city layouts,trained on velocity data generated by large-eddy simulations(LES)with the CityFFD solver.The results demonstrate that the FNO achieves accuracy comparable to CFD while reducing the per-frame wall-clock time from 2.210 s with CityFFD to 0.006 s on an NVIDIA V100 GPU,corresponding to an approximately 370x speedup.To further mitigate GPU memory constraints,a patch-based training strategy is introduced,which partitions the wind field into smaller spatial blocks,enabling the FNO to capture localized flow dynamics more effectively.In addition,incorporating signed distance function(SDF)data provides critical building-geometry information,thereby improving boundary recognition,enhancing prediction realism,and strengthening overall model generalizability.
基金Financial support from the Simulation-based Engineering Science(Genie Par la Simulation)program funded through the CREATE program from the Natural Sciences and Engineering Research Council of Canada is gratefully acknowledged.
文摘The simulation of rarefied gasflows through complex porous media is chal-lenging due to the tortuousflow pathways inherent to such structures.The Lattice Boltzmann method(LBM)has been identified as a promising avenue to solveflows through complex geometries due to the simplicity of its scheme and its high parallel computational efficiency.It has been proposed to model the stress-strain relationship with the extended Navier-Stokes equations rather than attempting to directly solve the Boltzmann equation.However,a regularization technique is required tofilter out non-resolved higher-order components with a low-order velocity scheme.Although slip boundary conditions(BCs)have been proposed for the non-regularized multiple relaxation time LBM(MRT-LBM)for planar geometries,previous slip BCs have never been verified extensively with the regularization technique.In this work,following an extensive literature review on the imposition of slip BCs for rarefiedflows with the LBM,it is proven that earlier values for kinetic parameters developed to impose slip BCs are inaccurate for the regularized MRT-LBM and differ between the D2Q9 and D3Q15 schemes.The error was eliminated for planarflows and good agreement be-tween analytical solutions for arrays of cylinders and spheres was found with a wide range of Knudsen numbers.
