Showing papers by "Sankaran Sundaresan published in 2009"
TL;DR: In this article, a drag law with improved accuracy has been established for bidisperse fixed beds and suspensions with particle-particle relative motions, where the particles are spherical and are intimately mixed.
Abstract: Lattice-Boltzmann simulations of low-Reynolds-number fluid flow in bidisperse fixed beds and suspensions with particle–particle relative motions have been performed. The particles are spherical and are intimately mixed. The total volume fraction of the suspension was varied between 0.1 and 0.4, the volume fraction ratio /1//2 from 1:1 to 1:6, and the particle size ratio d1/d2 from 1:1.5 to 1:4. A drag law with improved accuracy has been established for bidisperse fixed beds. For suspensions with particle– particle relative motions, the hydrodynamic particle–particle drag representing the momentum transfer between particle species through hydrodynamic interaction is found to be an important contribution to the net fluid-particle drag. It has a logarithmic dependence on the lubrication cutoff distance and can be fit as the harmonic mean of the drag forces in bidisperse fixed beds. The proposed drag laws for bidisperse fixed beds and suspensions are generalized to polydisperse suspensions with three or more particle species. V C 2009 American Institute of Chemical Engineers AIChE J, 55: 1352–1368, 2009
123 citations
TL;DR: In this article, the authors extended the low Reynolds number fluid-particle drag relation proposed by Yin and Sundaresan for polydisperse systems to include the effect of moderate fluid inertia.
Abstract: In this article, we extend the low Reynolds number fluid-particle drag relation proposed by Yin and Sundaresan for polydisperse systems to include the effect of moderate fluid inertia. The proposed model captures the fluid-particle drag results obtained from lattice-Boltzmann simulations of bidisperse and ternary suspensions at particle mixture Reynolds numbers ranging from 0 � Remix � 40, over a particle volume fraction range of 0.2 � f � 0.4, volume fraction ratios of 1 � fi/fj � 3, and particle diameter ratios of 1 � di/dj � 2.5. V C 2009 American Institute of Chemical Engineers AIChE J, 56: 1995–2004, 2010
85 citations
TL;DR: In this article, the authors constructed from lattice-Boltzmann simulations a drag correlation for bidisperse gas−solid suspensions containing equally sized particles that are moving with different velocities relative to the interstitial fluid.
Abstract: In this study, we constructed from lattice-Boltzmann simulations a drag correlation for bidisperse gas−solid suspensions containing equally sized particles that are moving with different velocities relative to the interstitial fluid. Our analysis is limited to flows at low Reynolds numbers and high Stokes numbers, and the microstructure of the suspension is identical to that of a hard-sphere fluid. The Stokes drag forces acting on the two particle species are related to the fluid−particle relative velocities by a friction coefficient matrix, the off-diagonal components of which represent the particle−particle drag due to hydrodynamic interactions and were found to give important contributions to the net drag force. The off-diagonals exhibit a logarithmic dependence on the lubrication cutoff distance, a length scale on which the lubrication force between approaching particles begins to level off. In our simulations, the total particle volume fraction ϕ ranges from 0.1 to 0.4, and the volume fraction ratio ...
73 citations
TL;DR: In this paper, the size distribution of fragmented nanopowders was characterized by online Scanning Mobility Particle Spectrometer (SMPS) and Aerodynamic Particle Sizer (APS).
Abstract: Deagglomeration of suspensions of alumina and titania nanopowders (i.e., nanoparticle aggregates) via rapid expansion of supercritical suspensions (RESS) or high-pressure suspensions (REHPS) was studied. The size distribution of fragmented nanopowders was characterized by online Scanning Mobility Particle Spectrometer (SMPS) and Aerodynamic Particle Sizer (APS), and by offline Scanning Electron Microscopy (SEM). SMPS and SEM measurements indicate that the average agglomerate sizes were well below 1 μm, consistent with the length scales observed in our complementary RESS/REHPS mixing experiments using alumina and silica nanopowders. The APS measurements, on the other hand, were affected by reagglomeration during sampling and yielded an agglomerate size range of 1 to 3 μm. Analysis of the RESS/REHPS process through compressible flow models revealed that both the shear stress in the nozzle and the subsequent impact of the agglomerates with the Mach disc in the free expansion region can lead to micron or sub-micron level deagglomeration. © 2009 American Institute of Chemical Engineers AIChE J, 2009
58 citations