Extensive changes can occur in alluvial river morphology over relatively short time periods due to such extreme events as a flash flood or flood resulting due to dam break or dike failure. In the present paper the results obtained through the application of a fully coupled one-dimensional alluvial river model are presented for simulation of such sharp hydraulic and bed transients in an alluvial river. Here the governing system of partial differential equations was discretized by making use of the generalized Preissmann finite difference scheme. The resulting set of non-linear partial difference equations was solved by using Newton-Raphson iterative procedure in which the solution for banded matrix of Jacobians was obtained through a hexa-diagonal solution algorithm. The model presented herein has been validated through a number of proofs of the concept tests and by simulating the Quail Creek Dike failure which occurred on 31 December 1988 and 1 January 1989 in Washington County, Utah, USA. The present model was further extended to simulate the processes of grain sorting, wash load transport and non-equilibrium sediment transport. The results obtained from these simulations are presented in this paper.
RÉSUMÉDe profonds changements de morphologie de fleuve alluvial peuvent se produire dans des périodes de temps relativement courtes à la suite d'événements extrêmes tels qu'une crue éclair ou une onde de rupture de barrage ou de digue Dans l'article présent, les résultats obtenus par l'application d'un modèle unidimensionnel de fleuve alluvial entièrement couplé sont présentés pour la simulation de tels transitoires pointus hydrauliques dans un lit de fleuve alluvial. Ici le système d'équations aux dérivées partielles a été discrétisé en se servant du schéma de différence fini de Preissmann généralisé. L'ensemble résultant d'équations aux différences finies non linéaires a été résolu en employant le procédé itératif de Newton-Raphson dans lequel la résolution de la matrice bande de Jacobiens a été obtenue par un algorithme de solution hexa-diagonal. Le modèle présenté ci-dessus a été validé par un certain nombre de preuves d'essais de concept et en simulant la rupture de la digue Quail Creek qui s'est produite le 31 décembre 1988 et 1er janvier 1989 dans le comté de Washington, Utah, Etats-Unis. Le modèle actuel a été ensuite prolongé pour simuler les processus de tri des grains, le transport par lessivage et le transport de sédiment non équilibré. Les résultats obtenus à partir de ces simulations sont présentés en cet article.
Einstein's field equations with variable gravitational and cosmological "constant" are considered in presence of perfect fluid for Bianchi type-I space-time. Consequences of the four cases of the phenomenological decay of Λ have been discussed which are consistent with observations. The physical significance of the cosmological models have also been discussed.
The present study deals with spatially homogeneous and totally anisotropic locally rotationally symmetric (LRS) Bianchi type I cosmological model with variable G and in presence of imperfect fluid. To get the deterministic model of Universe, we assume that the expansion (θ ) in the model is proportional to shear (σ ). This condition leads to A = B n , where A, B are metric potential. The cosmological constant is found to be decreasing function of time and it approaches a small positive value at late time which is supported by recent Supernovae Ia (SN Ia) observations. Also it is evident that the distance modulus curve of derived model matches with observations perfectly.
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