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Showing 2 results for Rostamzadeh khosroshahi
Alireza Rostamzadeh khosroshahi, Seied Esmaeel Razavi, Seyed Mehdi Mirsajedi,
Volume 18, Issue 6 (10-2018)
Abstract
Present study proposes a new multidimensional artificially characteristic-based (MACB) scheme for simulation of combined convection flows. Multidimensional characteristic structure for energy propagation in incompressible flow is derived for the first time. Four pseudo-waves are selected and equations are discretized along them to observe the physical behavior of domain. Viscous fluxes are computed by variables derivatives at the cell interfaces and for time discretization, a 4th-order Runge-Kutta method was used. According to the new scheme, two-dimensional flow with heat transfer in a square cavity and forced convection around a circular cylinder are solved for a wide range of Reynolds and Grashof numbers. Also, for comparison purposes, the CB scheme with averaging for energy equation is used. It was found that MACB has remarkable faster convergence in comparison with CB scheme and averaging methods. Also, by using MACB scheme, maximum permissible CFL number can be increased 80 percent in comparison to CB scheme. At higher Richardson numbers, the conventional flux averaging was failed to converge properly while MACB scheme presents the most rapid convergence. The computed results of MACB scheme are in good agreement with the benchmark solutions.
M. Aligholami , A. Rostamzadeh khosroshahi ,
Volume 19, Issue 10 (October 2019)
Abstract
The aim of this study is the modeling of the solar chimney for achieving the relation between turbine output power and geometrical parameters. In this regards, 9 different models are determined based on the variety of chimney height and diameter for investigating the effects of geometrical parameters on the turbine performance. As well as, in order to improvement of system performance, the hydrophobic surfaces were evaluated with consideration of friction reduction by verification of slip condition on walls. The k-ε turbulent model was used to modeling turbulence flow and reverse-fan model was employed for simulating the turbine. For this purpose, the extracted data from the mass flow rate and velocity changes were validated with prior studies and then were compared in different pressure jumps in order to better comprehension of the performance of the turbine. The optimization was done through the defined models and it was observed that to have a better and optimized design, the geometrical parameters should have been considered in the system design simultaneously. Meanwhile, the chimney diameter should have been paid more attention as one of the most important design parameters. Also, the precise correlation was represented to estimate the turbine output power with respect to the height and diameter of the chimney. Furthermore, based on the applying of slip condition on walls for simulating hydrophobic surfaces, shear stresses reduction was done and it was revealed that the hydrophobic surfaces could have a positive effect on the performance of SCPP up to 5 percent.