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Hydrodynamic Pressure (hydrodynamic + pressure)

Distribution by Scientific Domains

Engineering	80%

Selected Abstracts

Expression of non-signaling membrane-anchored death receptors protects murine livers in different models of hepatitis,,

HEPATOLOGY, Issue 2 2006
Delphyne Descamps
Fas and tumor necrosis factor receptor 1 (TNFR1) are death receptors involved in various diseases such as hepatitis, sepsis, or graft rejection. Neutralizing antibodies to death ligands or soluble death receptors can inhibit cell death; however, they induce side effects because of their systemic actions. To specifically block death signaling to target cells, we created death domain,deficient (,DD) membrane-anchored receptors, delivered to the liver by either recombinant adenovirus or hydrodynamic pressure of nonviral recombinant plasmids. In anti-Fas antibody-induced fulminant hepatitis, mice expressing recombinant Fas-decoy receptors (Fas,DD) in their livers were completely protected against apoptosis and survived fulminant hepatitis. In T-cell,dependent concanavalin A,induced autoimmune hepatitis, Fas,DD antagonist expression prevented hepatocyte damage and mouse death. Finally, TNFR1,DD effectively protected mice against LPS-induced septic shock. In conclusion, such ,DD-decoy receptors act as dominant-negative receptors exerting local inhibition, while avoiding systemic neutralization of apoptosis ligands, and might have therapeutic potential in hepatitis. (HEPATOLOGY 2006;44:399,409.) [source]

Multi-linearity algorithm for wall slip in two-dimensional gap flow

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 12 2007
G. J. Ma
Abstract Wall slip has been observed in a micro/nanometer gap during the past few years. It is difficult to make a mathematical analysis for the hydrodynamics of the fluid flowing in a gap with wall slip because the fluid velocity at the liquid,solid interface is not known a priori. This difficulty is met especially in a two-dimensional slip flow due to the non-linearity of the slip control equation. In the present paper we developed a multi-linearity method to approach the non-linear control equation of the two-dimensional slip gap flow. We used an amended polygon to approximate the circle yield (slip) boundary of surface shear stress. The numerical solution does not need an iterative process and can simultaneously give rise to fluid pressure distribution, wall slip velocity and surface shear stress. We analysed the squeeze film flow between two parallel discs and the hydrodynamics of a finite slider gap with wall slip. Our numerical solutions show that wall slip is first developed in the large pressure gradient zone, where a high surface shear stress is easily generated, and then the slip zone is enlarged with the increase in the shear rate. Wall slip dramatically affects generation of the hydrodynamic pressure. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Quadratic programming algorithm for wall slip and free boundary pressure condition

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 2 2006
C. W. Wu
Abstract Wall slip is often observed in a highly sheared fluid film in a solid gap. This makes a difficulty in mathematical analysis for the hydrodynamic effect because fluid velocity at the liquid,solid interfaces is not known a priori. If the gap has a convergent,divergent wedge, a free boundary pressure condition, i.e. Reynolds pressure boundary condition, is usually used in the outlet zone in numerical solution. This paper, based on finite element method and parametric quadratic programming technique, gives a numerical solution technique for a coupled boundary non-linearity of wall slip and free boundary pressure condition. It is found that the numerical error decreases with the number of elements in a negative power law having an index larger than 2. Our method does not need an iterative process and can simultaneously gives rise to fluid film pressure distribution, wall slip velocity and surface shear stress. Wall slip always decreases the hydrodynamic pressure. Large wall slip even causes a null hydrodynamic pressure in a pure sliding solid gap. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Three-dimensional numerical modelling of free surface flows with non-hydrostatic pressure

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 9 2002
Musteyde B. Koçyigit
Abstract A three-dimensional numerical model is developed for incompressible free surface flows. The model is based on the unsteady Reynolds-averaged Navier,Stokes equations with a non-hydrostatic pressure distribution being incorporated in the model. The governing equations are solved in the conventional sigma co-ordinate system, with a semi-implicit time discretization. A fractional step method is used to enable the pressure to be decomposed into its hydrostatic and hydrodynamic components. At every time step one five-diagonal system of equations is solved to compute the water elevations and then the hydrodynamic pressure is determined from a pressure Poisson equation. The model is applied to three examples to simulate unsteady free surface flows where non-hydrostatic pressures have a considerable effect on the velocity field. Emphasis is focused on applying the model to wave problems. Two of the examples are about modelling small amplitude waves where the hydrostatic approximation and long wave theory are not valid. The other example is the wind-induced circulation in a closed basin. The numerical solutions are compared with the available analytical solutions for small amplitude wave theory and very good agreement is obtained. Copyright © 2002 John Wiley & Sons, Ltd. [source]