Direct simulations of cells motions and deformations in flow

Direct numerical simulations (DNS) are used to study the motions and deformations of blood cells, especially leukocytes, in pressure driven flows in parallel plate channels with both smooth and uneven walls under adhesion force between the leukocytes and the channel wall. Leukocytes are represented by two composite fluid models. The first model is the compound-drop model in which the cytoplasm and the nucleus are modeled as fluids, and the second one is the drop-rigid-particle model in which the cytoplasm is modeled as a fluid and the nucleus as a rigid particle. The adhesion force is computed using two adhesion force models. In the first model, the adhesion force is given by a potential, and in the second model it is given by Dembo\u27s kinetic adhesion model. The numerical code is based on the finite element method and the level-set technique is used to track the cell membrane position. In the absence of the adhesion force, in a pressure driven flow the leukocyte moves away from the wall to an equilibrium location. In presence of the adhesion force, provided it is located within the range of the force, the leukocyte is attracted to the layer of endothelial cells and it flattens under the action of hydrodynamic forces. It is found that for the normal parameter values and flow rates the adhesive force given by the kinetic model is too small to capture the leukocyte. The time at which all bonds are broken and the leukocyte moves away from the wall increases when the capillary number is increased, and decreases with increasing Reynolds number. The former suggests that the adhesion tendency of a leukocyte increases as its cortical tension is reduced. The distance traveled by a leukocyte before all bonds are broken increases with the Reynolds and capillary numbers. The rolling velocity of the leukocyte near an uneven wall varies in the sense that it appears to slip when its lower surface is in the gap between the spheres and stick when it comes close to the spheres\u27 surfaces, which is in qualitative agreement with the experimental data

Recent Trends in Coatings and Thin Film–Modeling and Application

Over the past four decades, there has been increased attention given to the research of fluid mechanics due to its wide application in industry and phycology. Major advances in the modeling of key topics such Newtonian and non-Newtonian fluids and thin film flows have been made and finally published in the Special Issue of coatings. This is an attempt to edit the Special Issue into a book. Although this book is not a formal textbook, it will definitely be useful for university teachers, research students, industrial researchers and in overcoming the difficulties occurring in the said topic, while dealing with the nonlinear governing equations. For such types of equations, it is often more difficult to find an analytical solution or even a numerical one. This book has successfully handled this challenging job with the latest techniques. In addition, the findings of the simulation are logically realistic and meet the standard of sufficient scientific value

Bibliography of Lewis Research Center technical publications announced in 1988

This bibliography contains abstracts of the technical reports that resulted from the scientific and engineering work performed and managed by the Lewis Research Center in 1988. Subject, author, and corporate source indexes are also included. All the publications were announced in the 1988 issues of STAR (Scientific and Technical Aerospace Reports) and/or IAA (International Aerospace Abstracts). Included are research reports, journal articles, conference presentations, patents and patent applications, and theses

Numerical study of two-phase phenomena using OpenFOAM

An Open source “OpenFOAM” CFD modelling tool and multi-phase solvers are used to solve two-phase flow problems of relevance a variety of engineering applications. Validation of several benchmark two-phase model predictions is presented and discussed. For the different cases considered, the comparison showed that this CFD simulation tool is suitable for modelling multi-phase problems. Furthermore, the comparison revealed that the sclsVOFFoam (LS+VOF) solver is more accurate than interFoam (VOF) and showed better agreement with previous studies. Hence, it is concluded that OpenFOAM with the sclsVOFFoam (VOF+LS) solver is suitable for simulation of multi-phase problems, and so is chosen for implementation in this research study. Numerical studies of two multi-phase problems of practical significance are studied in detail, namely: (i) the coalescence of two droplets and (ii) the jet-burst phenomena of a high speed laminar jet. The numerical framework (geometrical, computational and physical settings) for the two problems are constructed and validated against relevant studies from literature. For the interaction of two droplets problem, numerical results are obtained for the flow phenomena to investigate the final composite droplet location at different lateral separation, impact speed and liquid properties (viscosity and surface tension). It is found that the composite droplet location (centre-of-mass ) relative to the initial condition (initial centre-of-mass) is influenced significantly by the impacting droplet velocity and liquid properties, but showed the same non-intuitive final location displacement for the three overlap ratios (lateral separation) studied in this research. For the high speed laminar jet problem, at ReL=2200, results are obtained for different inflow velocity profile, ambient gas viscosity and reduced liquid viscosity. From the results for the high speed laminar liquid jet, it is concluded that this is predominantly a laminar phenomenon, where the inlet velocity profile plays a critical role in determining burst onset. Secondary flow due to the axial velocity relaxation is found to be influential in determining the onset of the jet burst. Also, the results demonstrate that aerodynamic effects play a minimal role in influencing liquid jet burst characteristics. These results are useful in informing estimates of jet breakup length in practical problems, such as (explosive) area classification for accidental releases of high-flashpoint fuels

Bibliography of Lewis Research Center technical publications announced in 1986

This compilation of abstracts describes and indexes the technical reporting that resulted from the scientific and engineering work performed and managed by the Lewis Research Center in 1986. All the publications were announced in the 1986 issues of Scientific and Technical Aerospace Reports (STAR) and/or International Aerospace Abstracts (IAA). Included are research reports, journal articles, conference presentations, patents and patent applications, and theses

MS FT-2-2 7 Orthogonal polynomials and quadrature: Theory, computation, and applications

Quadrature rules find many applications in science and engineering. Their analysis is a classical area of applied mathematics and continues to attract considerable attention. This seminar brings together speakers with expertise in a large variety of quadrature rules. It is the aim of the seminar to provide an overview of recent developments in the analysis of quadrature rules. The computation of error estimates and novel applications also are described