The Experts below are selected from a list of 69132 Experts worldwide ranked by ideXlab platform
J M Mcdonough - One of the best experts on this subject based on the ideXlab platform.
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simulating flows with moving rigid boundary using immersed boundary method
Computers & Fluids, 2010Co-Authors: Chuanchieh Liao, Yuwei Chang, Chaoan Lin, J M McdonoughAbstract:Abstract The present study is to apply the immersed-boundary method to simulate 2- and 3-D viscous incompressible flows interacting with moving solid boundaries. Previous studies indicated that for stationary-boundary problems, different treatments inside the solid body did not affect the external flow. However, the relationship between internal treatment of the solid body and external flow for moving-boundary problems was not studied extensively and is investigated here. This is achieved via direct-momentum forcing on a Cartesian Grid by combining “solid-body forcing” at solid nodes and interpolation on neighboring fluid nodes. The influence of the solid body forcing within the solid nodes is first examined by computing flow induced by an oscillating cylinder in a stationary square domain, where significantly lower amplitude oscillations in computed lift and drag coefficients are obtained compared with those without solid-body-forcing strategy. Grid-Function convergence tests also indicate second-order accuracy of this implementation with respect to the L 1 norm in time and the L 2 norm in space. Further test problems are simulated to examine the validity of the present technique: 2-D flows over an asymmetrically-placed cylinder in a channel, in-line oscillating cylinder in a fluid at rest, in-line oscillating cylinder in a free stream, two cylinders moving with respect to one another, and 3-D simulation of a sphere settling under gravity in a static fluid. All computed results are in generally good agreement with various experimental measurements and with previous numerical simulations. This indicates the capability of the present simple implementation in solving complex-geometry flow problems and the importance of solid body forcing in computing flows with moving solid objects.
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using vorticity to define conditions at multiple open boundaries for simulating flow in a simplified vortex settling basin
International Journal for Numerical Methods in Fluids, 2007Co-Authors: Ali Naghi Ziaei, J M Mcdonough, Homayoun Emdad, Alireza KeshavarziAbstract:In this paper a method is developed to define multiple open boundary (OB) conditions in a simplified vortex settling basin (VSB). In this method, the normal component of the momentum equation is solved at the OBs, and tangential components of vorticity are calculated by solving vorticity transport equations only at the OBs. Then the tangential vorticity components are used to construct Neumann boundary conditions for tangential velocity components. Pressure is set to its ambient value, and the divergence-free condition is satisfied at these boundaries by employing the divergence as the Neumann condition for the normal-direction momentum equation. The 3-D incompressible Navier-Stokes equations in a primitive-variable form are solved using the SIMPLE algorithm. Grid-Function convergence tests are utilized to verify the numerical results. The complicated laminar flow structure in the VSB is investigated, and preliminary assessment of two popular turbulence models, k-e and k-m, is conducted.
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using vorticity to define conditions at multiple open boundaries for simulating flow in a simplified vortex settling basin
International Journal for Numerical Methods in Fluids, 2007Co-Authors: Ali Naghi Ziaei, J M Mcdonough, Homayoun Emdad, Alireza KeshavarziAbstract:In this paper a method is developed to define multiple open boundary (OB) conditions in a simplified vortex settling basin (VSB). In this method, the normal component of the momentum equation is solved at the OBs, and tangential components of vorticity are calculated by solving vorticity transport equations only at the OBs. Then the tangential vorticity components are used to construct Neumann boundary conditions for tangential velocity components. Pressure is set to its ambient value, and the divergence-free condition is satisfied at these boundaries by employing the divergence as the Neumann condition for the normal-direction momentum equation. The 3-D incompressible Navier-Stokes equations in a primitive-variable form are solved using the SIMPLE algorithm. Grid-Function convergence tests are utilized to verify the numerical results. The complicated laminar flow structure in the VSB is investigated, and preliminary assessment of two popular turbulence models, k-e and k-m, is conducted.
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an alternative discretization and solution procedure for the dual phase lag equation
Journal of Computational Physics, 2006Co-Authors: J M Mcdonough, Illayathambi Kunadian, Ravi Ranjan Kumar, T YangAbstract:We describe an alternative numerical treatment of the dual phase-lag equation often used to account for microscale, short-time heat transport. The approach consists of an undecomposed formulation of the partial differential equation resulting from Taylor expansion with respect to lag times of the original delay partial differential equation. Trapezoidal integration in time and centered differencing in space provide an accurate discretization, as demonstrated by comparisons with analytical and experimental results in one dimension, and via Grid-Function convergence tests in three dimensions. For relatively fine 3-D Grids the approach is approximately six times faster than a standard explicit scheme and nearly three times faster than an implicit method employing conjugate gradient iteration at each time step.
Alireza Keshavarzi - One of the best experts on this subject based on the ideXlab platform.
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using vorticity to define conditions at multiple open boundaries for simulating flow in a simplified vortex settling basin
International Journal for Numerical Methods in Fluids, 2007Co-Authors: Ali Naghi Ziaei, J M Mcdonough, Homayoun Emdad, Alireza KeshavarziAbstract:In this paper a method is developed to define multiple open boundary (OB) conditions in a simplified vortex settling basin (VSB). In this method, the normal component of the momentum equation is solved at the OBs, and tangential components of vorticity are calculated by solving vorticity transport equations only at the OBs. Then the tangential vorticity components are used to construct Neumann boundary conditions for tangential velocity components. Pressure is set to its ambient value, and the divergence-free condition is satisfied at these boundaries by employing the divergence as the Neumann condition for the normal-direction momentum equation. The 3-D incompressible Navier-Stokes equations in a primitive-variable form are solved using the SIMPLE algorithm. Grid-Function convergence tests are utilized to verify the numerical results. The complicated laminar flow structure in the VSB is investigated, and preliminary assessment of two popular turbulence models, k-e and k-m, is conducted.
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using vorticity to define conditions at multiple open boundaries for simulating flow in a simplified vortex settling basin
International Journal for Numerical Methods in Fluids, 2007Co-Authors: Ali Naghi Ziaei, J M Mcdonough, Homayoun Emdad, Alireza KeshavarziAbstract:In this paper a method is developed to define multiple open boundary (OB) conditions in a simplified vortex settling basin (VSB). In this method, the normal component of the momentum equation is solved at the OBs, and tangential components of vorticity are calculated by solving vorticity transport equations only at the OBs. Then the tangential vorticity components are used to construct Neumann boundary conditions for tangential velocity components. Pressure is set to its ambient value, and the divergence-free condition is satisfied at these boundaries by employing the divergence as the Neumann condition for the normal-direction momentum equation. The 3-D incompressible Navier-Stokes equations in a primitive-variable form are solved using the SIMPLE algorithm. Grid-Function convergence tests are utilized to verify the numerical results. The complicated laminar flow structure in the VSB is investigated, and preliminary assessment of two popular turbulence models, k-e and k-m, is conducted.
Michela Longo - One of the best experts on this subject based on the ideXlab platform.
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The Exploitation of Vehicle-to-Grid Function for Power Quality Improvement in a Smart Grid
IEEE Transactions on Intelligent Transportation Systems, 2014Co-Authors: Morris Brenna, Federica Foiadelli, Michela LongoAbstract:Smart Grids can be a good challenge for the near future if they are intelligently managed. Therefore, the exploitation of the energy resources distributed into a network is one of the most discussed themes in actual scientific literature, together with the attention paid to power quality (PQ) improvement. This paper aims to provide a possible solution to some common and dangerous PQ problems and voltage sags, considering the large diffusion of electric vehicles. A deep energy and power analysis to evaluate the feasibility of the vehicle-to-Grid (V2G) Function to compensate for PQ disturbances will be presented.
Ali Naghi Ziaei - One of the best experts on this subject based on the ideXlab platform.
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using vorticity to define conditions at multiple open boundaries for simulating flow in a simplified vortex settling basin
International Journal for Numerical Methods in Fluids, 2007Co-Authors: Ali Naghi Ziaei, J M Mcdonough, Homayoun Emdad, Alireza KeshavarziAbstract:In this paper a method is developed to define multiple open boundary (OB) conditions in a simplified vortex settling basin (VSB). In this method, the normal component of the momentum equation is solved at the OBs, and tangential components of vorticity are calculated by solving vorticity transport equations only at the OBs. Then the tangential vorticity components are used to construct Neumann boundary conditions for tangential velocity components. Pressure is set to its ambient value, and the divergence-free condition is satisfied at these boundaries by employing the divergence as the Neumann condition for the normal-direction momentum equation. The 3-D incompressible Navier-Stokes equations in a primitive-variable form are solved using the SIMPLE algorithm. Grid-Function convergence tests are utilized to verify the numerical results. The complicated laminar flow structure in the VSB is investigated, and preliminary assessment of two popular turbulence models, k-e and k-m, is conducted.
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using vorticity to define conditions at multiple open boundaries for simulating flow in a simplified vortex settling basin
International Journal for Numerical Methods in Fluids, 2007Co-Authors: Ali Naghi Ziaei, J M Mcdonough, Homayoun Emdad, Alireza KeshavarziAbstract:In this paper a method is developed to define multiple open boundary (OB) conditions in a simplified vortex settling basin (VSB). In this method, the normal component of the momentum equation is solved at the OBs, and tangential components of vorticity are calculated by solving vorticity transport equations only at the OBs. Then the tangential vorticity components are used to construct Neumann boundary conditions for tangential velocity components. Pressure is set to its ambient value, and the divergence-free condition is satisfied at these boundaries by employing the divergence as the Neumann condition for the normal-direction momentum equation. The 3-D incompressible Navier-Stokes equations in a primitive-variable form are solved using the SIMPLE algorithm. Grid-Function convergence tests are utilized to verify the numerical results. The complicated laminar flow structure in the VSB is investigated, and preliminary assessment of two popular turbulence models, k-e and k-m, is conducted.
Morris Brenna - One of the best experts on this subject based on the ideXlab platform.
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The Exploitation of Vehicle-to-Grid Function for Power Quality Improvement in a Smart Grid
IEEE Transactions on Intelligent Transportation Systems, 2014Co-Authors: Morris Brenna, Federica Foiadelli, Michela LongoAbstract:Smart Grids can be a good challenge for the near future if they are intelligently managed. Therefore, the exploitation of the energy resources distributed into a network is one of the most discussed themes in actual scientific literature, together with the attention paid to power quality (PQ) improvement. This paper aims to provide a possible solution to some common and dangerous PQ problems and voltage sags, considering the large diffusion of electric vehicles. A deep energy and power analysis to evaluate the feasibility of the vehicle-to-Grid (V2G) Function to compensate for PQ disturbances will be presented.
