Progress in Computational Fluid Dynamics, An International Journal http://www.inderscience.com/browse/index.php?journalID=23&year=2012&vol=12&issue=1 Inderscience Publishers Ltd en-uk Progress in Computational Fluid Dynamics, An International Journal 1468-4349 1741-5233 © 2012 Inderscience Publishers Ltd editor@inderscience.com https://www.inderscience.com/images/files/coverImgs/pcfd_scoverpcfd.jpg http://www.inderscience.com/browse/index.php?journalID=23&year=2012&vol=12&issue=1 http://www.inderscience.com/link.php?id=44849 Implicit filtering is a common procedure in Large Eddy Simulation (LES). Problems with implicit filtering have led to the development of an alternate method called explicit filtering. Most explicit filtering methods are expensive, but filtering the entire flow field is one of the least expensive methods. Closeness of the filter shape to the sharp cut-off is a significant parameter in this kind of filtering. The aim of this paper is to study the effects of the closeness of filter shape to the sharp cut-off on flow statistics and to compare the Pade-type filter with different discrete filters that have shapes close to the sharp cut-off. Turbulent channel flow was chosen for the simulations. The finite-volume method was used along with the PISO algorithm. Moreover, the second-order central difference scheme was applied for spatial derivations and the Crank-Nicolson method for time integration. The problem was solved by three different types of discrete filters, all of which had shapes close to the cut-off filter. The results suggest that the use of explicit filtering by sharp cut-off filters improves the specific statistics of the wall-bounded turbulent channel flow. Pade-type filters produced the most desirable results. Investigation of the explicit cutoff filtering in Large Eddy Simulation
N.M. Nouri; S. Yekani Motlagh; E. Yasari; N. Mobadersany
Progress in Computational Fluid Dynamics, An International Journal, Vol. 12, No. 1 (2012) pp. 1 - 10
Implicit filtering is a common procedure in Large Eddy Simulation (LES). Problems with implicit filtering have led to the development of an alternate method called explicit filtering. Most explicit filtering methods are expensive, but filtering the entire flow field is one of the least expensive methods. Closeness of the filter shape to the sharp cut-off is a significant parameter in this kind of filtering. The aim of this paper is to study the effects of the closeness of filter shape to the sharp cut-off on flow statistics and to compare the Pade-type filter with different discrete filters that have shapes close to the sharp cut-off. Turbulent channel flow was chosen for the simulations. The finite-volume method was used along with the PISO algorithm. Moreover, the second-order central difference scheme was applied for spatial derivations and the Crank-Nicolson method for time integration. The problem was solved by three different types of discrete filters, all of which had shapes close to the cut-off filter. The results suggest that the use of explicit filtering by sharp cut-off filters improves the specific statistics of the wall-bounded turbulent channel flow. Pade-type filters produced the most desirable results.

]]> 10.1504/PCFD.2012.044849 Progress in Computational Fluid Dynamics, An International Journal, Vol. 12, No. 1 (2012) pp. 1 - 10 N.M. Nouri; S. Yekani Motlagh; E. Yasari; N. Mobadersany School of Mechanical Engineering, Iran University of Science and Technology, Narmak, Tehran 16846, Iran. ' School of Mechanical Engineering, Iran University of Science and Technology, Narmak, Tehran 16846, Iran. ' School of Mechanical Engineering, Iran University of Science and Technology, Narmak, Tehran 16846, Iran. ' School of Mechanical Engineering, Iran University of Science and Technology, Narmak, Tehran 16846, Iran computational fluid dynamics CFD LES large eddy simulation sharp cut-off filters Pade-type filters explicit filtering turbulent channel flow finite volume method. 2012-01-11T23:20:50-05:00 12 1 1 10 2012-01-11T23:20:50-05:00 http://www.inderscience.com/link.php?id=44850 In Lattice-Boltzmann modelling of shallow water flows, an approach for a constant discharge Q<SUB align="right">in at the inflow and a fixed water depth h<SUP align="right">*</SUP> at the outflow is proposed in this paper. It maintains the prescribed conditions, meanwhile keeps the variables consistent with those outside the flow domain. The effectiveness of the approach is demonstrated by two numerical tests: flows in a straight channel and in a divergent channel. Inlet and outlet boundary conditions for the Lattice-Boltzmann modelling of shallow water flows
H. Liu; J.G. Zhou; R. Burrows
Progress in Computational Fluid Dynamics, An International Journal, Vol. 12, No. 1 (2012) pp. 11 - 18
In Lattice-Boltzmann modelling of shallow water flows, an approach for a constant discharge Q<SUB align="right">in at the inflow and a fixed water depth h<SUP align="right">*</SUP> at the outflow is proposed in this paper. It maintains the prescribed conditions, meanwhile keeps the variables consistent with those outside the flow domain. The effectiveness of the approach is demonstrated by two numerical tests: flows in a straight channel and in a divergent channel.

]]> 10.1504/PCFD.2012.044850 Progress in Computational Fluid Dynamics, An International Journal, Vol. 12, No. 1 (2012) pp. 11 - 18 H. Liu; J.G. Zhou; R. Burrows State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, 19 Xinjiekou Wai Street, Beijing 100875, China. ' Department of Engineering, University of Liverpool, Liverpool L69 3GQ, UK. ' Department of Engineering, University of Liverpool, Liverpool L69 3GQ, UK ?ow boundary conditions Lattice Boltzmann method shallow water flows LABSWE modelling straight channels divergent channels. 2012-01-11T23:20:50-05:00 12 1 11 18 2012-01-11T23:20:50-05:00 http://www.inderscience.com/link.php?id=44851 In this paper, a three-dimensional vortex filament method is implemented to study the axis-switching period of an elliptic vortex ring. The change of the semi-axis length and the projection of a single elliptic ring are first compared with the literature. Then, the evolution of elliptic vortex rings with different circulations, aspect ratios and core radius-to-ring radius ratios are numerically reproduced, and the evolution of the velocity and aspect ratios are also studied to determine their influence on the motion of vortex rings. Furthermore, the axis-switching periods of elliptic rings for different cases are investigated, and an expression to fit all the cases is obtained. Numerical investigation of the evolution of elliptic vortex ring
Zhiwei Wang; Bin Chen
Progress in Computational Fluid Dynamics, An International Journal, Vol. 12, No. 1 (2012) pp. 19 - 26
In this paper, a three-dimensional vortex filament method is implemented to study the axis-switching period of an elliptic vortex ring. The change of the semi-axis length and the projection of a single elliptic ring are first compared with the literature. Then, the evolution of elliptic vortex rings with different circulations, aspect ratios and core radius-to-ring radius ratios are numerically reproduced, and the evolution of the velocity and aspect ratios are also studied to determine their influence on the motion of vortex rings. Furthermore, the axis-switching periods of elliptic rings for different cases are investigated, and an expression to fit all the cases is obtained.

]]> 10.1504/PCFD.2012.044851 Progress in Computational Fluid Dynamics, An International Journal, Vol. 12, No. 1 (2012) pp. 19 - 26 Zhiwei Wang; Bin Chen State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, China No. 28, Xianning West Road, Xi'an, Shaanxi 710049, China. ' State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, China No. 28, Xianning West Road, Xi'an, Shaanxi 710049, China vortex filament methods elliptic vortex rings axis-switching period circulation aspect ratio core radius-to-ring radius ratio. 2012-01-11T23:20:50-05:00 12 1 19 26 2012-01-11T23:20:50-05:00 http://www.inderscience.com/link.php?id=44852 In this paper, the Meshless Local Petrov-Galerkin (MLPG) method is applied to compute convection-dominated flow problems. The results of the MLPG method are compared with the results of the finite volume method. The results show that the first-order upwind (FUD) scheme exhibits the false diffusion at a larger-Peclet number; the QUICK scheme and the MLPG method can obtain much closed solutions; but they have small overshoots produced at larger-Peclet number. The results also indicate that the MLPG method is a highly effective and accurate numerical method to deal with convection-dominated flow problems and can eliminate the effect of the false diffusion. MLPG method for convection-dominated flow problems
Xue-Hong Wu; Zhi-Juan Chang; Wen-Quan Tao; Zeng-Yao Li; Sheng-Ping Shen
Progress in Computational Fluid Dynamics, An International Journal, Vol. 12, No. 1 (2012) pp. 27 - 36
In this paper, the Meshless Local Petrov-Galerkin (MLPG) method is applied to compute convection-dominated flow problems. The results of the MLPG method are compared with the results of the finite volume method. The results show that the first-order upwind (FUD) scheme exhibits the false diffusion at a larger-Peclet number; the QUICK scheme and the MLPG method can obtain much closed solutions; but they have small overshoots produced at larger-Peclet number. The results also indicate that the MLPG method is a highly effective and accurate numerical method to deal with convection-dominated flow problems and can eliminate the effect of the false diffusion.

]]> 10.1504/PCFD.2012.044852 Progress in Computational Fluid Dynamics, An International Journal, Vol. 12, No. 1 (2012) pp. 27 - 36 Xue-Hong Wu; Zhi-Juan Chang; Wen-Quan Tao; Zeng-Yao Li; Sheng-Ping Shen School of Electromechanical Science and Engineering, Zhengzhou University of Light Industry, Zhengzhou, Henan 450002, China; Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China. ' School of Food and Biological Engineering, Zhengzhou University of Light Industry, Zhengzhou, Henan 450002, China. ' School of Energy and Power Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China. ' School of Energy and Power Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China. ' School of Energy and Power Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China MLPG meshless local Petrov-Galerkin MLS moving least squares Smith-Hutton problem overshoots convection-dominated flow finite volume method. 2012-01-11T23:20:50-05:00 12 1 27 36 2012-01-11T23:20:50-05:00 http://www.inderscience.com/link.php?id=44853 It is known that reverse flow occurs in a channel when there is an obstruction at the entry. However, it has been recently shown that the reverse flow can be realised even without an obstruction. This is achieved when the two sides of the channel have a stagger and are kept at an angle of attack to the free stream. The features of the computed reverse flow agree with the experimental results. The computations show that the pumping mechanism of reverse flow in the present case can be explained by the relatively lower pressure near the entry to the channel and the slightly higher pressure near the exit of the channel. The low pressure region, near the entry to the channel, having staggered walls and kept at an angle of attack, is generated by the flow separation at the leading edge of the bottom wall of the channel. A numerical study on the mechanism of reverse flow in a channel without obstruction at the entry
M.G. Ju; C.H. Sohn; B.H.L. Gowda; E.G. Tulapurkara
Progress in Computational Fluid Dynamics, An International Journal, Vol. 12, No. 1 (2012) pp. 37 - 45
It is known that reverse flow occurs in a channel when there is an obstruction at the entry. However, it has been recently shown that the reverse flow can be realised even without an obstruction. This is achieved when the two sides of the channel have a stagger and are kept at an angle of attack to the free stream. The features of the computed reverse flow agree with the experimental results. The computations show that the pumping mechanism of reverse flow in the present case can be explained by the relatively lower pressure near the entry to the channel and the slightly higher pressure near the exit of the channel. The low pressure region, near the entry to the channel, having staggered walls and kept at an angle of attack, is generated by the flow separation at the leading edge of the bottom wall of the channel.

]]> 10.1504/PCFD.2012.044853 Progress in Computational Fluid Dynamics, An International Journal, Vol. 12, No. 1 (2012) pp. 37 - 45 M.G. Ju; C.H. Sohn; B.H.L. Gowda; E.G. Tulapurkara School of Mechanical Engineering, Kyungpook National University, Daegu 702-701, Korea. ' School of Mechanical Engineering, Kyungpook National University, Daegu 702-701, Korea. ' School of Mechanical Engineering, Kyungpook National University, Daegu 702-701, Korea. ' Department of Aerospace Engineering, IIT Madras, Chennai 600036, Tamil Nadu, India reverse flow channels staggered sides unsteady flow angle of attack flow separation. 2012-01-11T23:20:50-05:00 12 1 37 45 2012-01-11T23:20:50-05:00 http://www.inderscience.com/link.php?id=44854 The effects of buoyancy-aiding or buoyancy-opposing mechanisms on laminar mixed convection heat transfer in a porous enclosure partially cooled from the left vertical wall has been analysed numerically for two different forms of thermal boundary conditions in steady-state regime using the Darcy-Brinkman-Forchheimer equation model. In the first case, top wall of the cavity moves from left to right (buoyancy-aiding) with constant speed but in the second case bottom wall moves in the same direction (buoyancy-opposing). In both cases, sliding wall has higher temperature than that of half of the left wall while remaining walls are insulated. Finite-volume-based finite difference method with Simple algorithm was applied to solve the governing equations. The Richardson number, Ri, in the range 0.05 ≤ Ri ≤ 10, Darcy number Da = 0.1, 0.01 and 0.001, and porosity 0.2 ≤ ε ≤ 0.6 are chosen as values of the dimensionless governing parameters. It is found that when bottom wall moves, an opposing mechanism is formed. Higher Nusselt numbers are obtained than that of aiding mechanism (moving top wall) for all values of the Darcy numbers. Mixed convection in partially cooled lid-driven cavity filled with a non-Darcy porous medium
Hakan F. Oztop; Yasin Varol; Ioan Pop; Khaled Al-Saleem
Progress in Computational Fluid Dynamics, An International Journal, Vol. 12, No. 1 (2012) pp. 46 - 55
The effects of buoyancy-aiding or buoyancy-opposing mechanisms on laminar mixed convection heat transfer in a porous enclosure partially cooled from the left vertical wall has been analysed numerically for two different forms of thermal boundary conditions in steady-state regime using the Darcy-Brinkman-Forchheimer equation model. In the first case, top wall of the cavity moves from left to right (buoyancy-aiding) with constant speed but in the second case bottom wall moves in the same direction (buoyancy-opposing). In both cases, sliding wall has higher temperature than that of half of the left wall while remaining walls are insulated. Finite-volume-based finite difference method with Simple algorithm was applied to solve the governing equations. The Richardson number, Ri, in the range 0.05 ≤ Ri ≤ 10, Darcy number Da = 0.1, 0.01 and 0.001, and porosity 0.2 ≤ ε ≤ 0.6 are chosen as values of the dimensionless governing parameters. It is found that when bottom wall moves, an opposing mechanism is formed. Higher Nusselt numbers are obtained than that of aiding mechanism (moving top wall) for all values of the Darcy numbers.

]]> 10.1504/PCFD.2012.044854 Progress in Computational Fluid Dynamics, An International Journal, Vol. 12, No. 1 (2012) pp. 46 - 55 Hakan F. Oztop; Yasin Varol; Ioan Pop; Khaled Al-Saleem Technology Faculty, Department of Mechanical Engineering, F?rat University, TR-23119, Elazig, Turkey; Department of Mechanical Engineering, College of Engineering, King Saud University, Riyadh, Saudi Arabia. ' Technology Faculty, Department of Mechanical Engineering, F?rat University, TR-23119, Elazig, Turkey. ' Faculty of Mathematics, University of Cluj, R-3400 Cluj, CP 253, Romania. ' Department of Mechanical Engineering, College of Engineering, King Saud University, Riyadh, Saudi Arabia lid-driven cavity non-Darcy porous medium numerical solution mixed convectionm partially cooled cavity laminar mixed convection heat transfer porous enclosures thermal boundary conditions finite difference method buoyancy. 2012-01-11T23:20:50-05:00 12 1 46 55 2012-01-11T23:20:50-05:00 http://www.inderscience.com/link.php?id=44855 A numerical analysis for free convection boundary layers along a permeable vertical flat surface with prescribed power-law temperature distribution T<SUB align="right">w(x) = T<SUB align="right">∞ + Ax<SUP align="right">k</SUP> at y = 0 embedded in a fluid-saturated porous medium and subjected to an applied lateral mass flux proportional to the x<SUP align="right"> k-1/2</SUP> quantity is presented. We provide detailed comparisons by considering both analytical and numerical findings of previous authors, and a very good agreement is encountered. The results obtained elucidate reliability and efficiency of the technique. Heat and fluid flow past a vertical plate with lateral mass flux in a porous medium
Rafael Cortell
Progress in Computational Fluid Dynamics, An International Journal, Vol. 12, No. 1 (2012) pp. 56 - 65
A numerical analysis for free convection boundary layers along a permeable vertical flat surface with prescribed power-law temperature distribution T<SUB align="right">w(x) = T<SUB align="right">∞ + Ax<SUP align="right">k</SUP> at y = 0 embedded in a fluid-saturated porous medium and subjected to an applied lateral mass flux proportional to the x<SUP align="right"> k-1/2</SUP> quantity is presented. We provide detailed comparisons by considering both analytical and numerical findings of previous authors, and a very good agreement is encountered. The results obtained elucidate reliability and efficiency of the technique.

]]> 10.1504/PCFD.2012.044855 Progress in Computational Fluid Dynamics, An International Journal, Vol. 12, No. 1 (2012) pp. 56 - 65 Rafael Cortell Departamento de Física Aplicada, Escuela Técnica Superior de Ingenieros de Caminos, Canales y Puertos, Universidad Politécnica de Valencia, 46071 Valencia, Spain laminar boundary layers free convection porous media heat transfer fluid flow vertical plates lateral mass flux. 2012-01-11T23:20:50-05:00 12 1 56 65 2012-01-11T23:20:50-05:00