| 1. |
- Fukagata, K., et al.
(författare)
-
Anomalous velocity fluctuations in particulate turbulent channel flow
- 2001
-
Ingår i: International Journal of Multiphase Flow. - 0301-9322 .- 1879-3533. ; 27:4, s. 701-719
-
Tidskriftsartikel (refereegranskat)abstract
- Gas-particle turbulent channel flow at Re-tau = 644, loaded with copper particles at a mass flow ratio of 2%, is studied numerically by large eddy simulation (LES) coupled with Lagrangian particle tracking (LPT), Inter-particle collisions and correction of drag force in the vicinity of walls are accounted for. Focus is made on the influence of particle wall boundary conditions and their influence on the statistical structure of the flow, It is shown that accordance with experimental data can be improved if a mechanism which can suppress the direct re-entrainment of particles after the impact at the wall is present. Present result shows that inter-particle collisions may play an important role in the re-distribution of particle momentum among different components even at low mass loading conditions,
|
|
| 2. |
|
|
| 3. |
- Fukagata, K., et al.
(författare)
-
Dynamics of Brownian particles in a turbulent channel flow
- 2004
-
Ingår i: Heat and Mass Transfer. - : Springer Science and Business Media LLC. - 0947-7411 .- 1432-1181. ; 40:9, s. 715-726
-
Tidskriftsartikel (refereegranskat)abstract
- Turbulent channel flows with suspended particles are investigated by means of numerical simulations. The fluid velocity is computed by large eddy simulation. Motion of small graphite particles with diameter of 0.01-10 mum, corresponding to the Schmidt number, Sc, of 2.87 x 10(2)-6.22 x 10(6) and the particle relaxation time in wall unit, tau(p)(+), of 9.79 x 10(-5)-4.51, is computed by Lagrangian particle tracking. Relation between the particle relaxation time and the computed deposition velocity is found to be in good agreement with an empirical relation. The statistics of the particle motion in the vicinity of the wall are studied. Clear differences are found in dynamical behavior of particles with different sizes. Medium size particles show a strong dependence on the structure of the fluid flow, while small and large particles are considerably less sensitive.
|
|
| 4. |
- Gurniki, F., et al.
(författare)
-
LES of turbulent channel flow of a binary electrolyte
- 2000
-
Ingår i: Journal of Applied Electrochemistry. - 0021-891X .- 1572-8838. ; 30:12, s. 1335-1343
-
Tidskriftsartikel (refereegranskat)abstract
- The turbulent diffusion boundary layer in a binary electrolyte was considered at Schmidt numbers of 1, 10 and 100 and exchange current densities between 10(-4) A m(-2) and 10(-2) A m(-2). A numerical scheme was developed for efficient investigation of the dynamics by means of large eddy simulations. The methodology was examined by detailed comparisons with documented data from earlier large eddy and direct numerical simulations and good agreement was found. Application of the methodology to electrochemical mass transfer indicated that the exchange current density seems to have negligible effect on the mean concentration profile but it influences the structure of the fluctuating field in a visible manner.
|
|
| 5. |
- Lilja, L, et al.
(författare)
-
Cyclin-dependent kinase 5 promotes insulin exocytosis
- 2001
-
Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 276:36, s. 34199-34205
-
Tidskriftsartikel (refereegranskat)abstract
- Cyclin-dependent kinase 5 (Cdk5) is widely expressed although kinase activity has been described preferentially in neuronal systems. Cdk5 has an impact on actin polymerization during neuronal migration and neurite outgrowth and deregulation of the kinase has been implicated in the promotion of neurodegeneration. Recently it was shown that Cdk5 modulates dopamine signaling in neurons by regulating DARPP-32 function. In addition, Cdk5 phosphorylates munc-18 and synapsin I, two essential components of the exocytotic machinery. We have shown by reverse transcriptase-polymerase chain reaction, immunocytochemistry, and Western blotting that Cdk5 is present in the insulin-secreting pancreatic beta-cell. Subcellular fractionation of isolated beta-cells revealed a glucose-induced translocation of membrane-bound Cdk5 protein to lower density fractions. Inhibition of Cdk5 with roscovitine reduced insulin secretion with approximately 35% compared with control after glucose stimulation and with approximately 65% after depolarization with glucose and KCl. Capacitance measurements performed on single beta-cells that expressed a dominant-negative Cdk5 mutant showed impaired exocytosis. The effect on exocytosis by Cdk5 appeared to be independent of changes in free cytoplasmic Ca(2+) concentration. Taken together these results show that Cdk5 is present in beta-cells and acts as a positive regulator of insulin exocytosis.
|
|
| 6. |
- Widlund, O., et al.
(författare)
-
Structure information in rapid distortion analysis and one-point modeling of axisymmetric magnetohydrodynamic turbulence
- 2000
-
Ingår i: Physics of fluids. - : AIP Publishing. - 1070-6631 .- 1089-7666. ; 12:10, s. 2609-2620
-
Tidskriftsartikel (refereegranskat)abstract
- It has recently been suggested that dimensionality information, as carried by the Reynolds dimensionality tensor, should be included in an extended Reynolds stress closure for modeling of magnetohydrodynamic (MHD) turbulence at low magnetic Reynolds numbers. This would enable more accurate modeling of the Joule dissipation, and capture the length-scale anisotropies and tendencies towards two-dimensionality characteristic of MHD turbulence. In the present work, an evolution equation for the Reynolds dimensionality tensor is derived, based on the spectral formulation of the Navier-Stokes equations. Most of the terms in the equation require modeling. Rapid distortion theory (RDT) is applied to study the behavior of the different magnetic terms of the dimensionality and Reynolds stress tensor equations; a variety of different anisotropy states could be examined by letting magnetic forcing act on a number of initial spectral energy distributions obtained from axisymmetric strain. The properties and limitations of linear or bilinear invariant tensor models for the magnetic terms are evaluated. In the limit of large interaction numbers (where Joule dissipation dominates), the resulting model equations for the energy decay have analytic solutions. By choosing one model constant appropriately, these are made consistent with the asymptotic energy decay K similar to t(-1/2) predicted earlier by Moffatt. The long-term objective of these efforts is the development of an effective second-moment closure for engineering applications.
|
|
