One of the largest known megafloods on earth resulted from a glacier dam-break,which occurred during the Late Quaternary in the Altai Mountains in Southern Siberia.Computational modeling is one of the viable approache...One of the largest known megafloods on earth resulted from a glacier dam-break,which occurred during the Late Quaternary in the Altai Mountains in Southern Siberia.Computational modeling is one of the viable approaches to enhancing the understanding of the flood events.The computational domain of this flood is over 9460 km2 and about 3.784 × 106 cells are involved as a 50 m × 50 m mesh is used,which necessitates a computationally efficient model.Here the Open MP(Open Multiprocessing) technique is adopted to parallelize the code of a coupled 2D hydrodynamic and sediment transport model.It is shown that the computational efficiency is enhanced by over 80% due to the parallelization.The floods over both fixed and mobile beds are well reproduced with specified discharge hydrographs at the dam site.Qualitatively,backwater effects during the flood are resolved at the bifurcation between the Chuja and Katun rivers.Quantitatively,the computed maximum stage and thalweg are physically consistent with the field data of the bars and deposits.The effects of sediment transport and morphological evolution on the flood are considerable.Sensitivity analyses indicate that the impact of the peak discharge is significant,whilst those of the Manningroughness,medium sediment size and shape of the inlet discharge hydrograph are marginal.展开更多
A 10 m long,0.2 m wide flume was employed to simulate the channel bed evolution of check-dam failure.The experiment longitudinal profiles,the gradient of channel bed,head-cutting propagation distance and deposition le...A 10 m long,0.2 m wide flume was employed to simulate the channel bed evolution of check-dam failure.The experiment longitudinal profiles,the gradient of channel bed,head-cutting propagation distance and deposition length were compared with the theoretical solution derived from a sediment transport diffusion equation.In contrast with the theoretical solution,two different gradients were obtained upstream and downstream of the check-dam.The theoretical solution provides a good description of the changes upstream of the check-dam. The ratio of clear water depth to sediment moving layer thickness in the experiment was analyzed and showed that high concentration sediment laden flow was taken in the incipient of check-dam failure,which may be the reason why the experiment result was slightly different from the theoretical solution in the downstream of check-dam.展开更多
Glacier-lake outburst debris flow(GLODF),unique in high altitude mountains where modern glacier is active,is significantly large in its scale of time and space,and strong in power of destroy.Following the world's ...Glacier-lake outburst debris flow(GLODF),unique in high altitude mountains where modern glacier is active,is significantly large in its scale of time and space,and strong in power of destroy.Following the world's becoming warmer,GLODF frequency gradually rises.In late years,quantitative estimation methodologies has been put into use of mass GLODF estimations.To improve former methodologies,this article suggests that the glacier(or the massif)on the trailing edge and the moraine dam are the two major systems providing independent glacier lake outburst possibilities.Bucket Effect exists in GLODF issues.Therefore focusing on the relatively unstable one of the above two provides better accuracy in estimation on GLODF possibility.Thus,this article summarizes method of presort through specific GLODF evaluation.展开更多
基金funded by Natural Science Foundation of China (Grants No. 11172217 and 11432015)National Key Basic Research and Development Program (i.e., 973 Program) of China (Grant No. 2007CB714106)
文摘One of the largest known megafloods on earth resulted from a glacier dam-break,which occurred during the Late Quaternary in the Altai Mountains in Southern Siberia.Computational modeling is one of the viable approaches to enhancing the understanding of the flood events.The computational domain of this flood is over 9460 km2 and about 3.784 × 106 cells are involved as a 50 m × 50 m mesh is used,which necessitates a computationally efficient model.Here the Open MP(Open Multiprocessing) technique is adopted to parallelize the code of a coupled 2D hydrodynamic and sediment transport model.It is shown that the computational efficiency is enhanced by over 80% due to the parallelization.The floods over both fixed and mobile beds are well reproduced with specified discharge hydrographs at the dam site.Qualitatively,backwater effects during the flood are resolved at the bifurcation between the Chuja and Katun rivers.Quantitatively,the computed maximum stage and thalweg are physically consistent with the field data of the bars and deposits.The effects of sediment transport and morphological evolution on the flood are considerable.Sensitivity analyses indicate that the impact of the peak discharge is significant,whilst those of the Manningroughness,medium sediment size and shape of the inlet discharge hydrograph are marginal.
文摘A 10 m long,0.2 m wide flume was employed to simulate the channel bed evolution of check-dam failure.The experiment longitudinal profiles,the gradient of channel bed,head-cutting propagation distance and deposition length were compared with the theoretical solution derived from a sediment transport diffusion equation.In contrast with the theoretical solution,two different gradients were obtained upstream and downstream of the check-dam.The theoretical solution provides a good description of the changes upstream of the check-dam. The ratio of clear water depth to sediment moving layer thickness in the experiment was analyzed and showed that high concentration sediment laden flow was taken in the incipient of check-dam failure,which may be the reason why the experiment result was slightly different from the theoretical solution in the downstream of check-dam.
文摘Glacier-lake outburst debris flow(GLODF),unique in high altitude mountains where modern glacier is active,is significantly large in its scale of time and space,and strong in power of destroy.Following the world's becoming warmer,GLODF frequency gradually rises.In late years,quantitative estimation methodologies has been put into use of mass GLODF estimations.To improve former methodologies,this article suggests that the glacier(or the massif)on the trailing edge and the moraine dam are the two major systems providing independent glacier lake outburst possibilities.Bucket Effect exists in GLODF issues.Therefore focusing on the relatively unstable one of the above two provides better accuracy in estimation on GLODF possibility.Thus,this article summarizes method of presort through specific GLODF evaluation.
