A new flux-based hybrid subcell-remapping algorithm for staggered multimaterial arbitrary Lagrangian-Eulerian (MMALE) methods is presented. This new method is an effective generalization of the original subcell-remapp...A new flux-based hybrid subcell-remapping algorithm for staggered multimaterial arbitrary Lagrangian-Eulerian (MMALE) methods is presented. This new method is an effective generalization of the original subcell-remapping method to the multi-material regime (LOUBERE, R. and SHASHKOV,M. A subcell remapping method on staggered polygonal grids for arbitrary-Lagrangian-Eulerian methods. Journal of Computational Physics, 209, 105–138 (2005)). A complete remapping procedure of all fluid quantities is described detailedly in this paper. In the pure material regions, remapping of mass and internal energy is performed by using the original subcell-remapping method. In the regions near the material interfaces, remapping of mass and internal energy is performed with the intersection-based fluxes where intersections are performed between the swept regions and pure material polygons in the Lagrangian mesh, and an approximate approach is then introduced for constructing the subcell mass fluxes. In remapping of the subcell momentum, the mass fluxes are used to construct the momentum fluxes by multiplying a reconstructed velocity in the swept region. The nodal velocity is then conservatively recovered. Some numerical examples simulated in the full MMALE regime and several purely cyclic remapping examples are presented to prove the properties of the remapping method.展开更多
The ERA-Interim reanalysis wind based on the distance-weighted average remapping for studying the wind circulation in Nigeria is presented. The wind flow using this atmospheric model simulation is studied for identifi...The ERA-Interim reanalysis wind based on the distance-weighted average remapping for studying the wind circulation in Nigeria is presented. The wind flow using this atmospheric model simulation is studied for identification of grid-tie electrification opportunities in different wind locations. A 10-year reanalysis wind speed components at a surface level of the planetary layer at 0.25° × 0.25° spatial resolution is obtained and remapped into a new horizontal wind field at a grid resolution of 0.125° × 0.125° covering longitudinal and latitudinal directions of 3.0 - 15.0°E and 15.0 - 3.0°N, respectively. Using the distance-weighted average technique, the remapped wind field at a new grid resolution of 0.125° × 0.125° is compared at different terrain elevations and approximated close to the actual wind field of the same resolution. To determine the suitability of the prevailing wind for small-scale energy conversion, the magnitude of wind flow across the remapped wind field is studied for a 10-year period. Analysis shows that northern regions of Nigeria have a fair wind potential for a stand-alone application based on the wind flow originated at Gulf of Guinea as well as Chad and Niger. Furthermore, hourly surface wind speed observations from 18 synoptic stations in Nigeria are obtained and compared with the bilinear interpolated wind stations. The reanalysis wind reflects the surface wind observations and proves that the prevailing wind in Nigeria is higher than the reanalysis wind projection obtained from gridded data at resolution of 0.125° × 0.125°. The sectorwise wind directions at each synoptic stations for a period of 10 years are presented.展开更多
The arbitrary Lagrangian-Eulerian(ALE)method is widely used in the field of compressible multi-material and multi-phase flow problems.In order to implement the indirect ALE approach for the simulation of compressible ...The arbitrary Lagrangian-Eulerian(ALE)method is widely used in the field of compressible multi-material and multi-phase flow problems.In order to implement the indirect ALE approach for the simulation of compressible flow in the context of high order discontinuous Galerkin(DG)discretizations,we present a high order positivity-preserving DG remapping method based on a moving mesh solver in this paper.This remapping method is based on the ALE-DG method developed by Klingenberg et al.[17,18]to solve the trivial equation∂u/∂t=0 on a moving mesh,which is the old mesh before remapping at t=0 and is the new mesh after remapping at t=T.An appropriate selection of the final pseudo-time T can always satisfy the relatively mild smoothness requirement(Lipschitz continuity)on the mesh movement velocity,which guarantees the high order accuracy of the remapping procedure.We use a multi-resolution weighted essentially non-oscillatory(WENO)limiter which can keep the essentially non-oscillatory property near strong discontinuities while maintaining high order accuracy in smooth regions.We further employ an effective linear scaling limiter to preserve the positivity of the relevant physical variables without sacrificing conservation and the original high order accuracy.Numerical experiments are provided to illustrate the high order accuracy,essentially non-oscillatory performance and positivity-preserving of our remapping algorithm.In addition,the performance of the ALE simulation based on the DG framework with our remapping algorithm is examined in one-and two-dimensional Euler equations.展开更多
It is found that the solution remapping technique proposed in[Numer.Math.Theor.Meth.Appl.,2020,13(4)]and[J.Sci.Comput.,2021,87(3):1-26]does not work out for the Navier-Stokes equations with a high Reynolds number.The ...It is found that the solution remapping technique proposed in[Numer.Math.Theor.Meth.Appl.,2020,13(4)]and[J.Sci.Comput.,2021,87(3):1-26]does not work out for the Navier-Stokes equations with a high Reynolds number.The shape deformations usually reach several boundary layer mesh sizes for viscous flow,which far exceed one-layer mesh that the original method can tolerate.The direct application to Navier-Stokes equations can result in the unphysical pressures in remapped solutions,even though the conservative variables are within the reasonable range.In this work,a new solution remapping technique with lower bound preservation is proposed to construct initial values for the new shapes,and the global minimum density and pressure of the current shape which serve as lower bounds of the corresponding variables are used to constrain the remapped solutions.The solution distribution provided by the present method is proven to be acceptable as an initial value for the new shape.Several numerical experiments show that the present technique can substantially accelerate the flow convergence for large deformation problemswith 70%-80%CPU time reduction in the viscous airfoil drag minimization.展开更多
A two-stage automatic key frame selection method is proposed to enhance stitching speed and quality for UAV aerial videos. In the first stage, to reduce redundancy, the overlapping rate of the UAV aerial video sequenc...A two-stage automatic key frame selection method is proposed to enhance stitching speed and quality for UAV aerial videos. In the first stage, to reduce redundancy, the overlapping rate of the UAV aerial video sequence within the sampling period is calculated. Lagrange interpolation is used to fit the overlapping rate curve of the sequence. An empirical threshold for the overlapping rate is then applied to filter candidate key frames from the sequence. In the second stage, the principle of minimizing remapping spots is used to dynamically adjust and determine the final key frame close to the candidate key frames. Comparative experiments show that the proposed method significantly improves stitching speed and accuracy by more than 40%.展开更多
基金Project supported by the China Postdoctoral Science Foundation(No.2017M610823)
文摘A new flux-based hybrid subcell-remapping algorithm for staggered multimaterial arbitrary Lagrangian-Eulerian (MMALE) methods is presented. This new method is an effective generalization of the original subcell-remapping method to the multi-material regime (LOUBERE, R. and SHASHKOV,M. A subcell remapping method on staggered polygonal grids for arbitrary-Lagrangian-Eulerian methods. Journal of Computational Physics, 209, 105–138 (2005)). A complete remapping procedure of all fluid quantities is described detailedly in this paper. In the pure material regions, remapping of mass and internal energy is performed by using the original subcell-remapping method. In the regions near the material interfaces, remapping of mass and internal energy is performed with the intersection-based fluxes where intersections are performed between the swept regions and pure material polygons in the Lagrangian mesh, and an approximate approach is then introduced for constructing the subcell mass fluxes. In remapping of the subcell momentum, the mass fluxes are used to construct the momentum fluxes by multiplying a reconstructed velocity in the swept region. The nodal velocity is then conservatively recovered. Some numerical examples simulated in the full MMALE regime and several purely cyclic remapping examples are presented to prove the properties of the remapping method.
文摘The ERA-Interim reanalysis wind based on the distance-weighted average remapping for studying the wind circulation in Nigeria is presented. The wind flow using this atmospheric model simulation is studied for identification of grid-tie electrification opportunities in different wind locations. A 10-year reanalysis wind speed components at a surface level of the planetary layer at 0.25° × 0.25° spatial resolution is obtained and remapped into a new horizontal wind field at a grid resolution of 0.125° × 0.125° covering longitudinal and latitudinal directions of 3.0 - 15.0°E and 15.0 - 3.0°N, respectively. Using the distance-weighted average technique, the remapped wind field at a new grid resolution of 0.125° × 0.125° is compared at different terrain elevations and approximated close to the actual wind field of the same resolution. To determine the suitability of the prevailing wind for small-scale energy conversion, the magnitude of wind flow across the remapped wind field is studied for a 10-year period. Analysis shows that northern regions of Nigeria have a fair wind potential for a stand-alone application based on the wind flow originated at Gulf of Guinea as well as Chad and Niger. Furthermore, hourly surface wind speed observations from 18 synoptic stations in Nigeria are obtained and compared with the bilinear interpolated wind stations. The reanalysis wind reflects the surface wind observations and proves that the prevailing wind in Nigeria is higher than the reanalysis wind projection obtained from gridded data at resolution of 0.125° × 0.125°. The sectorwise wind directions at each synoptic stations for a period of 10 years are presented.
基金supported in part by NSFC grant 12031001National Key R&D Program of China No.2023YFA1009003supported in part by NSF grant DMS-2010107.
文摘The arbitrary Lagrangian-Eulerian(ALE)method is widely used in the field of compressible multi-material and multi-phase flow problems.In order to implement the indirect ALE approach for the simulation of compressible flow in the context of high order discontinuous Galerkin(DG)discretizations,we present a high order positivity-preserving DG remapping method based on a moving mesh solver in this paper.This remapping method is based on the ALE-DG method developed by Klingenberg et al.[17,18]to solve the trivial equation∂u/∂t=0 on a moving mesh,which is the old mesh before remapping at t=0 and is the new mesh after remapping at t=T.An appropriate selection of the final pseudo-time T can always satisfy the relatively mild smoothness requirement(Lipschitz continuity)on the mesh movement velocity,which guarantees the high order accuracy of the remapping procedure.We use a multi-resolution weighted essentially non-oscillatory(WENO)limiter which can keep the essentially non-oscillatory property near strong discontinuities while maintaining high order accuracy in smooth regions.We further employ an effective linear scaling limiter to preserve the positivity of the relevant physical variables without sacrificing conservation and the original high order accuracy.Numerical experiments are provided to illustrate the high order accuracy,essentially non-oscillatory performance and positivity-preserving of our remapping algorithm.In addition,the performance of the ALE simulation based on the DG framework with our remapping algorithm is examined in one-and two-dimensional Euler equations.
基金This project is supported by the National Natural Science Foundation of China(No.12001031).
文摘It is found that the solution remapping technique proposed in[Numer.Math.Theor.Meth.Appl.,2020,13(4)]and[J.Sci.Comput.,2021,87(3):1-26]does not work out for the Navier-Stokes equations with a high Reynolds number.The shape deformations usually reach several boundary layer mesh sizes for viscous flow,which far exceed one-layer mesh that the original method can tolerate.The direct application to Navier-Stokes equations can result in the unphysical pressures in remapped solutions,even though the conservative variables are within the reasonable range.In this work,a new solution remapping technique with lower bound preservation is proposed to construct initial values for the new shapes,and the global minimum density and pressure of the current shape which serve as lower bounds of the corresponding variables are used to constrain the remapped solutions.The solution distribution provided by the present method is proven to be acceptable as an initial value for the new shape.Several numerical experiments show that the present technique can substantially accelerate the flow convergence for large deformation problemswith 70%-80%CPU time reduction in the viscous airfoil drag minimization.
文摘A two-stage automatic key frame selection method is proposed to enhance stitching speed and quality for UAV aerial videos. In the first stage, to reduce redundancy, the overlapping rate of the UAV aerial video sequence within the sampling period is calculated. Lagrange interpolation is used to fit the overlapping rate curve of the sequence. An empirical threshold for the overlapping rate is then applied to filter candidate key frames from the sequence. In the second stage, the principle of minimizing remapping spots is used to dynamically adjust and determine the final key frame close to the candidate key frames. Comparative experiments show that the proposed method significantly improves stitching speed and accuracy by more than 40%.
