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Moradi Larmaei M.,Montreal Polytechnic Institute | Mahdi T.-F.,Montreal Polytechnic Institute
Environmental Hydraulics - Proceedings of the 6th International Symposium on Environmental Hydraulics | Year: 2010

In finite volume SIMPLE algorithm a collocated data structure causes numerical oscillation in pressure field. When SIMPLE algorithm is utilized, the discretized 2D and 2D depth averaged equations have the same forms. In a 2D depth averaged simulation, the pressure field is identical to water surface elevation and, in turn, an oscillation in pressure field cusses an oscillation in water surface elevation. To date, the Rhie and Chow's pressure interpolation technique is the only affordable method in order to have a smooth pressure field and the relevant water surface elevation. The main argument is, whether the Rhie and Chow's pressure interpolation technique is successful enough for 2D depth averaged simulations or not. Results of present research reveal that the checkerboard oscillations are more significant at higher Reynolds numbers, and they cannot be adequately removed by Rhie and Chow's pressure interpolation technique. © 2010 Taylor & Francis Group, London.


Moradi Larmaei M.,Montreal Polytechnic Institute | Mahdi T.-F.,Montreal Polytechnic Institute
International Journal of Heat and Mass Transfer | Year: 2012

In this article, the latest developments of porous media science are used in order to simulate heat and fluid flow in a non-flexible vegetated porous media. Vegetation porosity and density at the domain interior are redefined. The same strategy is then applied in order to define the boundary porosity near the bed and water surface. Regarding the vegetation arrangement in natural streams and flumes, three different models are suggested for calculating the porosity near other boundaries. The microscopic time-mean secondary force in momentum equations is modified for a vegetated porous media and its macroscopic form is derived. A dissipation source term is derived and, it is added to vorticity equation in order to take account of vegetation damping effect on secondary flows. The effect of this dissipation source term on the absolute magnitude of vorticity and velocity field is then investigated. Application of a high Reynolds number turbulence model to turbulent flow in partially vegetated open channels is numerically examined. A model is suggested for taking account of vegetation material on heat flux through walls in a vegetated porous media. The thermal diffusion due to the porosity gradient is modeled and, the contribution of this porosity-induced heat flux on temperature field is investigated. The effect of laminar thermal dispersion on temperature field is also investigated at low stem Reynolds number. © 2011 Elsevier Ltd. All rights reserved.


Larmaei M.M.,Montreal Polytechnic Institute | Behzadi J.,Shahid Chamran University | Mahdi T.-F.,Montreal Polytechnic Institute
Numerical Heat Transfer, Part B: Fundamentals | Year: 2010

In this article, a new concept, "local triangle", is described. A smoother pressure field is then obtained through the utilization of local triangles in a multiblock local triangulation method. The cell face velocity is corrected with a pressure-correction term which is usually underrelaxed. It is demonstrated that this relaxation factor has to be one, and it cannot be the general relaxation factor. It is indicated that the checkerboard oscillations are more significant at higher cell Reynolds numbers and, in turn, in this article, numerical simulations are mainly performed in turbulent flow. Copyright © Taylor & Francis Group, LLC.


Larmaei M.M.,Montreal Polytechnic Institute | Behzadi J.,Golestan University | Mahdi T.-F.,Montreal Polytechnic Institute
International Journal for Numerical Methods in Fluids | Year: 2012

In this article, the depth-averaged transport equations are written in a new way so that it is possible to solve the transport equations for very small water depths. Variables are interpolated into the cell face with two different schemes and, the schemes are compared in terms of computational cost and accuracy. The bed source terms are computed using two different assumptions. The effect of these assumptions on numerical simulations is then investigated. Solutions of transport equations on different types of unstructured triangular grids are compared and, an appropriate choice of grid is suggested. © 2011 John Wiley & Sons, Ltd.

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