The Experts below are selected from a list of 50550 Experts worldwide ranked by ideXlab platform
Federico E Teruel - One of the best experts on this subject based on the ideXlab platform.
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validity of the Macroscopic Energy equation model for laminar flows through porous media developing and fully developed regions
International Journal of Thermal Sciences, 2017Co-Authors: Federico E TeruelAbstract:Abstract The performance of the Macroscopic Energy equation model for laminar flows through porous media is tested and analyzed in this study. This is achieved by comparing the behavior of the model with data obtained from microscopic numerical simulations. These simulations correspond to a flow that is heated by a constant temperature boundary condition at the fluid-solid interface in a simple porous structure formed by staggered square cylinders. Specifically, laminar steady flow regimes with ReD = 1, 10 and 75, PeD in the 10-104 range, and porosities between 55 and 95% are simulated. Applying the cellular average to the numerical solution allows obtaining the Macroscopic temperature. Results clearly show the existence of two different regions at a Macroscopic scale. At the entrance, there is a thermally developing region characterized by a rapid variation of the temperature with the streamwise coordinate. The second region is the fully developed region where the non-dimensional temperature varies exponentially with the streamwise coordinate. The length of the developing region is found to be relatively large for high PeD numbers allowing to conclude that the thermal entrance effect cannot be neglected in the use of Macroscopic models for large PeD numbers. The model is also tested in the fully developed region showing excellent agreement with the data. It is found that the decay rate of the Macroscopic temperature in this region scales with P e D − 0.8 and that the exponent is fairly independent of the porosity, flow conditions and fluid properties. Finally, it is shown that models that ignore the entrance region or neglect thermal dispersion are, in general, not valid.
Marcelo J S De Lemos - One of the best experts on this subject based on the ideXlab platform.
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a correlation for interfacial heat transfer coefficient for turbulent flow over an array of square rods
Journal of Heat Transfer-transactions of The Asme, 2006Co-Authors: Marcelo B Saito, Marcelo J S De LemosAbstract:Interfacial heat transfer coefficients in a porous medium modeled as a staggered array of square rods are numerically determined. High and low Reynolds k-e turbulence models are used in conjunction of a two-Energy equation model, which in chides distinct transport equations for the fluid and the solid phases. The literature has documented proposals for Macroscopic Energy equation modeling for porous media considering the local thermal equilibrium hypothesis and laminar flow. In addition, two-Energy equation models have been proposed for conduction and laminar convection in packed beds. With the aim of contributing to new developments, this work treats turbulent heat transport modeling in porous media under the local thermal nonequilibrium assumption. Macroscopic time-average equations for continuity, momentum, and Energy are presented based on the recently established double decomposition concept (spatial deviations and temporal fluctuations of flow properties). The numerical technique employed for discretizing the governing equations is the control volume method. Turbulent flow results for the Macroscopic heat transfer coefficient, between the fluid and solid phase in a periodic cell, are presented.
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interfacial heat transfer coefficient for non equilibrium convective transport in porous media
International Communications in Heat and Mass Transfer, 2005Co-Authors: Marcelo B Saito, Marcelo J S De LemosAbstract:The literature has documented proposals for Macroscopic Energy equation modeling for porous media considering the local thermal equilibrium hypothesis and laminar flow. In addition, two-Energy equation models have been proposed for conduction and laminar convection in packed beds. With the aim of contributing to new developments, this work treats turbulent heat transport modeling in porous media under the local thermal non-equilibrium assumption. Macroscopic time-average equations for continuity, momentum and Energy are presented based on the recently established double decomposition concept (spatial deviations and temporal fluctuations of flow properties). Interfacial heat transfer coefficients are numerically determined for an infinite medium over which the fully developed flow condition prevails. The numerical technique employed for discretizing the governing equations is the control volume method. Preliminary laminar flow results for the Macroscopic heat transfer coefficient, between the fluid and solid phase in a periodic cell, are presented.
Earl T Campbell - One of the best experts on this subject based on the ideXlab platform.
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a theory of single shot error correction for adversarial noise
Quantum Science and Technology, 2019Co-Authors: Earl T CampbellAbstract:Single-shot error correction is a technique for correcting physical errors using only a single round of noisy check measurements, such that any residual noise affects a small number of qubits. We propose a general theory of single-shot error correction and establish a sufficient condition called good soundness of the code's measurement checks. Good code soundness in topological (or low-density parity check, LDPC) codes is shown to entail a Macroscopic Energy barrier for the associated Hamiltonian. Consequently, 2D topological codes with local checks can not have good soundness. In tension with this, we also show that for any code a specific choice of measurement checks does exist that provides good soundness. In other words, every code can perform single-shot error correction but the required checks may be nonlocal and act on many qubits. If we desire codes with both good soundness and simple measurement checks (the LDPC property) then careful constructions are needed. Finally, we use a double application of the homological product to construct quantum LDPC codes with single-shot error correcting capabilities. Our double homological product codes exploit redundancy in measurements checks through a process we call metachecking.
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a theory of single shot error correction for adversarial noise
arXiv: Quantum Physics, 2018Co-Authors: Earl T CampbellAbstract:Single-shot error correction is a technique for correcting physical errors using only a single round of noisy check measurements, such that any residual noise affects a small number of qubits. We propose a general theory of single-shot error correction and establish a sufficient condition called good soundness of the code's measurement checks. Good code soundness in topological (or LDPC) codes is shown to entail a Macroscopic Energy barrier for the associated Hamiltonian. Consequently, 2D topological codes with local checks can not have good soundness. In tension with this, we also show that for any code a specific choice of measurement checks does exist that provides good soundness. In other words, every code can perform single-shot error correction but the required checks may be nonlocal and act on many qubits. If we desire codes with both good soundness and simple measurement checks (the LDPC property) then careful constructions are needed. Finally, we use a double application of the homological product to construct quantum LDPC codes with single-shot error correcting capabilities. Our double homological product codes exploit redundancy in measurements checks through a process we call metachecking.
Suman Chakraborty - One of the best experts on this subject based on the ideXlab platform.
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an enthalpy source based lattice boltzmann model for conduction dominated phase change of pure substances
International Journal of Thermal Sciences, 2008Co-Authors: Dipankar Chatterjee, Suman ChakrabortyAbstract:An enthalpy-source based novel lattice Boltzmann technique is formulated for numerical simulation of conduction-dominated phase change processes of single-component systems. The proposed model is based on a classical lattice Boltzmann scheme for description of internal Energy evolution with a fixed-grid enthalpy-based formulation for capturing the phase boundary evolution in an implicit fashion. A single particle density distribution function is used for calculating the thermal variable. The Macroscopic Energy equation is found to be recovered following the Chapman–Enskog multiscale expansion procedure. It is also found that predictions from the present model agree excellently with results obtained from established analytical/numerical models.
S M Kresta - One of the best experts on this subject based on the ideXlab platform.
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distribution of Energy between convective and turbulent flow for 3 frequently used impellers
Chemical Engineering Research & Design, 1996Co-Authors: G Zhou, S M KrestaAbstract:Turbulence Energy dissipation is important in the study of turbulent mixing phenomena in stirred tanks. This paper investigates the characteristics of the turbulence Energy dissipation and the overall Energy distribution in the impeller region of a stirred tank. One radial flow impeller (Rushton turbine (RT)) and two axial flow impellers (the pitched blade turbine (PBT) and a fluidfoil turbine (A310)) were used. The mean and root-mean-square velocity (RMS) profiles close to the three impellers were measured in a cylindrical baffled tank using laser Doppler anemometry (LDA). The average turbulence Energy dissipation, e i was calculated using a Macroscopic Energy balance equation over several control volumes. The local turbulence Energy dissipation e was estimated using e=Av 3 /L with A=1 and L=D/10. Integration of the local dissipation over a control volume consistently gave results within 6% of the Macroscopic Energy balance. The bulk of the Energy is dissipated in the small volume occupied by the impeller and the impeller discharge stream for all three impellers: in order of increasing percentages 38.1% (A310), 43.5% (RT) and 70.5% (PBT). The dominant characteristics of Energy distribution are different for each impeller. The A310 was most efficient at generating convective flow. The RT generated the most turbulence, and the PBT derived a much larger portion of its Energy from the return flow.
