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Dube, S. K.; Sinha, P. C.; Rao, G. S.; Rao, A. D.
doi: 10.1002/fld.1650151002pmid: N/A
A three‐dimensional numerical model has been applied to study the impact of freshwater discharge from a river on the coastal circulation in the western Bay of Bengal. The basic dynamical framework of the model follows closely that described by Johns et al.1 for the simulation of coastal upwelling off the east coast of India. Using this model, experiments have been performed to investigate the impact of the freshwater discharge at the location of Godavari river along the east coast of India. A comparison of the model results, with and without the inclusion of river discharge, shows that the river discharge into the western Bay of Bengal suppresses the upwelling near the river mouth. Though there are no detailed observations on the flow structure near the mouth of the Godavari river, the computed results are in qualitative agreement with the observations documented by Rao and Jayaraman2 and Rao,3 who have shown that during monsoon period the upwelling off Godavari estuary is suppressed.
Chen, Yiping; Falconer, Roger A.
doi: 10.1002/fld.1650151003pmid: N/A
In recent years the QUICK finite difference scheme has been increasingly used in solving the advection‐diffusion equation, particularly for water quality modelling studies relating to coastal and estuarine flows. This scheme has the benefits of mass conservation, reasonably high accuracy and computational efficiency in comparison with many other higher‐order‐accurate schemes reported in the recent literature. A von Neumann stability analysis showed that the explicit QUICK scheme has a severe stability constraint which depends upon the diffusion coefficient. It can be proved that this scheme is numerically unstable for the case of pure advection. Various modified forms of the implicit QUICK scheme have been formulated and their numerical stability properties have been studied and analysed. The modified QUICK schemes considered have been tested for transient simulations for the cases of pure advection and of advection and diffusion in an idealized one‐dimensional basin using three different initial boundary conditions: (a) a sharp front concentration gradient, (b) a Gaussian concentration distribution and (c) a plug source. Details of the comparisons between these modified schemes and with other typical second‐order‐accurate difference schemes are given, together with comparisons with the analytical solutions for each case. A two‐dimensional version of the semi‐time‐centred QUICK scheme (ADI‐QUICK), has also been applied to a two‐dimensional test case using the standard ADI technique and has been shown to be attractive in comparison with other comparable second‐order schemes.
Chuang, Shu‐Hao; Lin, Hsun‐Cheng; Chen, Ming‐Hua; Jan, Jin‐Fa
doi: 10.1002/fld.1650151004pmid: N/A
The combustion flow of a sudden‐expansioin dump combustor with injecting side‐inlet is analysed using the SIMPLE‐C algorithm and the Jones‐Launder k‐ϵ two‐equation turbulence model. The transport properties of velocity, turbulence kinetic energy, temperature and combustion efficiency as a function of the injected mass fraction and the number of side‐inlet nozzles are solved in this paper. The axial velocities of the sudden‐expansion dump combustor without injected side‐inlet flow are solved first and found to be in good agreement with the experimental data of Moon and Rudinger. For a fixed value of the side‐inlet number the wall temperature and combustion efficiency of the dump combustor are decreased when the injected mass fraction is increased. For a fixed value of the injected mass fraction the wall temperature and combustion efficiency are decreased when the number of side‐inlet nozzles is increased.
Takizawa, Akihiko; Koshizuka, Seiichi; Kondo, Shunsuke
doi: 10.1002/fld.1650151005pmid: N/A
This paper presents a systematic and theoretically consistent approach for the analysis of free‐surface flow, making use of a number of established ideas such as physical component, boundary‐fitted co‐ordinate (BFC) and Lagrangian front tracking. The approach extends, theoretically as well as numerically, the use of physical component to general non‐orthogonal moving grids and provides a numerically stable BFC method with little labour of free‐surface positioning, grid generation and grid renewal. The approach conserves mass even at the free surface and allows time step of the order of the Coulant number. The main body of the present paper starts with the definition of analytical space and Riemannian geometry intrinsic to the physical component by applying to it the theorems of differential geometry and manifold theory. Then the governing equations of flow and free surface for the physical component are defined in the general 3D form with the notation of the new Riemannian geometry. Numerical procedures and the fully discrete equations are also presented for the benefit of potential users. Finally, several 2D examples demonstrate the basic performance of the present method by showing the computability of complex free‐surface motion.
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