Simulation of particle collection by model fiber filters

Computer simulations of particle deposition in model fiber filters were conducted. The basic element of the model filters used in the simulation consisted of three identical parallel and equally spaced circular cylinders, with the flow field around the cylinder obtained using the method of Lehner. The deposition process was simulated using the method developed earlier by the present author. The procedure was further modified by including an adhesion mechanism. Both monodispersed and polydispersed aerosols were considered. The results of the simulation agreed with the available experimental data.     

Laminar flow inside hexagonal ducts

Analytical solutions are obtained for fully developed laminar flow inside hexagonal ducts and, as a special case, rhombic ducts, through application of the recently advanced generalized integral transform technique for the solution of diffusion-type problems within irregular domains. First, the formal complete solution of the original problem is obtained, in terms of a denumerable system of coupled ordinary differential equations. Then, an explicit and quite straightforward lowest order solution results from the appropriate simplification of the coupled system. Quantities of particular interest in the field of heat exchanger thermohydraulics are then systematically presented, and utilized to establish the accuracy and suggest application ranges for the approximate solution.Communicated by S. N. Atluri, May 11, 1989     

Laminar flow of thin liquid films

Theoretical and experimental papers on the hydrodynamics of laminar liquid films moving along sloping surfaces are analyzed. The Nusselt theory is the asymptotic solution of the complete system of Navier-Stokes equations.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 27, No. 4, pp. 702–706, October, 1974.     

Stability of ferrofluid flow between concentric rotating cylinders with an axial magnetic field

A linear stability analysis for the ferrofluid flow between two concentric rotating cylinders in the presence of an axial magnetic field is implemented in this study. Both of the wide-gap and small-gap cases are considered and the governing equations with respect to three-dimensional disturbances including axisymmetric and non-axisymmetric modes are derived and solved by a direct numerical procedure. A parametric study covering wide ranges of ?, the volume fraction of colloidal particles; ξ, the strength of axial magnetic field; μ, the ratio of angular velocity of the outer cylinder to that of the inner cylinder; and ε, the ratio of radius of the inner cylinder to that of the outer cylinder, is conducted. Results show that the stability characteristics depend heavily on these factors. It is found that the increases of ? and ξ, and decrease of ε tend to stabilize the basic flow for an assigned value of μ. The variations of the onset mode with these parameters are discussed in detail. An example for the practical application of present results is given to help the understanding of stability behaviour of this flow.     

Laminar flow meter with straight glass capillary

The Center for Measurement Standards (CMS) developed a laminar flow meter (LFM) as a transfer standard. This LFM consists of a single, straight glass capillary or multiple straight glass capillaries connected in parallel. Two gauges and one thermometer measure the inlet/outlet pressure and inlet temperature, respectively, and the differential pressure was restricted to between 2 kPa and 100 kPa. The glass capillaries were manufactured by laser machining, which resulting in consistent inner diameter and straight flow path. Characteristics of the glass material also prevented the capillary from bending during installation. The LFMs were calibrated against the CMS piston prover primary standard and the calibration data were fitted using a theoretical LFM model and a 2nd order polynomial. The turndown ratio of this approach was higher than 20 and the residuals were within 0.11%. The reproducibility/repeatability within 0.03% indicated that this LFM could be used as a transfer standard. Measurement with dry air demonstrated that these four LFE meters could span flows from 0.8 to 986 μmol/s within the deviation of ± 0.15% (1μmol/s is 1.3 cm³/min at 0°C and 101.325 kPa). Additional measurement with nitrogen demonstrated the feasibility of measurement with multiple gases.     

Laminar flow in a narrow cylindrical tube

Laminar flows during periodic pressure drops and transverse oscillations of the liquid-solid interface are discussed.     

Laminar vapor flow in a heat pipe

Laminar vapor flow in the evaporation, adiabatic, and condensation sections of a heat pipe is considered. The problem is solved by using a parametric method. The solution resulted in a graphoanalytical method of determining the vapor-pressure loss in all sections of the pipe.     

Count time series prediction using particle filters

Non‐Gaussian dynamic models are proposed to analyse time series of counts. Three models are proposed for responses generated by a Poisson, a negative binomial, and a mixture of Poisson distributions. The parameters of these distributions are allowed to vary dynamically according to state space models. Particle filters or sequential Monte Carlo methods are used for inference and forecasting purposes. The performance of the proposed methodology is evaluated by two simulation studies for the Poisson and the negative binomial models. The methodology is illustrated by considering data consisting of medical contacts of schoolchildren suffering from asthma in England.     

Laminar two-dimensional entrance region flow of power-law fluids

Summary An approximate solution for the prediction of the power-law fluid flow behaviour in the entrance region of a straight channel has been presented. This has been achieved by solving a hydrodynamically equivalent model of developing two-dimensional Newtonian flow in a channel by momentum integral method. The analysis leads to closed form expressions for the flow characteristics. A comparison of the predictions with other solutions has also been incorporated.With 3 Figures     

Laminar entrace region flow of the Bingham fluid

Acta Mechanica - The chief purpose of this paper is to solve numerically the entrance region flow of the Bingham fluid by omitting the necessity of pre-assuming the form of velocity profile within...     

A micromechanical model to predict the flow of soft particle glasses

Soft particle glasses form a broad family of materials made of deformable particles, as diverse as microgels, emulsion droplets, star polymers, block copolymer micelles and proteins, which are jammed at volume fractions where they are in contact and interact via soft elastic repulsions. Despite a great variety of particle elasticity, soft glasses have many generic features in common. They behave like weak elastic solids at rest but flow very much like liquids above the yield stress. This unique feature is exploited to process high-performance coatings, solid inks, ceramic pastes, textured food and personal care products. Much of the understanding of these materials at volume fractions relevant in applications is empirical, and a theory connecting macroscopic flow behaviour to microstructure and particle properties remains a formidable challenge. Here we propose a micromechanical three-dimensional model that quantitatively predicts the nonlinear rheology of soft particle glasses. The shear stress and the normal stress differences depend on both the dynamic pair distribution function and the solvent-mediated EHD interactions among the deformed particles. The predictions, which have no adjustable parameters, are successfully validated with experiments on concentrated emulsions and polyelectrolyte microgel pastes, highlighting the universality of the flow properties of soft glasses. These results provide a framework for designing new soft additives with a desired rheological response.     

Laminar flow with injection in a straight duct

The velocity distribution and pressure drop associated with injection flow in a straight duct are analyzed on the basis of exact solutions of the Navier-Stokes equations.     

Laminar forced convection in wedge flow with separation

Abstract

A perturbation method is used to study the steady and unsteady laminar boundary layer heat transfer from a wedge with separation for a step‐discontinuity in the surface temperature. The analytic solutions obtained can be used to calculate the steady and unsteady heat transfer rate with arbitrary surface temperature. The effects of the Prandtl number on the temperature distribution and the heat transfer rate are discussed in detail. The solution is valid for large or moderate Prandtl number.     

Numerical and analytical study of rotating flow in an enclosed cylinder under an axial magnetic field

Summary. A numerical and analytical study of the steady laminar flow driven by a rotating disk at the top of an enclosed cylinder, having an aspect ratio H/R equal to 1, filled with a liquid metal, and submitted to an axial magnetic field B, is presented. The governing equations in cylindrical coordinates are solved by a finite volume method. In the absence of a magnetic field, the numerical method is validated via a comparison with experimental data; the latter was found to be in good agreement with the predictions. In the presence of a magnetic field, the analytical velocity profiles under the rotating disk and on the bottom wall obtained for a high value of the magnetic interaction parameter N are in excellent agreement with those obtained by numerical simulations. The effect of the top, bottom and vertical walls' conductivity on the flow is studied and found to be an important parameter in the control of the flow.     

Laminar flow in a channel with a step

Summary In this paper we investigated numerically the laminar flow of a homogeneous, viscous incompressible liquid, through a channel with a step. We used one numerical approach for small Reynolds numbers, and a different method for large numbers. Streamlines were calculated with high accuracy using a relatively small amount of computer time.     

Design of three-dimensional superresolution filters and limits of axial optical superresolution

Theories to design a three-dimensional superresolution filter (TDSF) for confocal microscopy are proposed that can obtain a globally optimal solution through linear programming. The designed TDSF is proved to be a phase-only element introducing a phase delay of 0 or pi. Five design examples of the TDSF are presented to demonstrate the validity of these theories, Regardless of transverse superresolution, a curve of Seu(Ga+/-) defined as the maximum value of Strehl ratio S under the axial resolving power of Ga+/- is calculated to set the fundamental limits of axial optical superresolution. Finally, what is to our knowledge a novel analytic expression of Seu(Ga+/-) is deduced.     

Investigation of rice grain flow by multi-sphere particle model with rolling resistance

A multi-sphere (MS) model combined with rolling friction was considered for modelling elongated particles of irregular shape. The performance of the model was investigated by numerical simulations of the rice grain flow. A set of 5000 poly-dispersed milled rice grains were selected for the investigation purposes. They were characterised by a constant aspect ratio 3.5, while their maximum size was ranging from 6.4 to 7.3 mm. Filling and discharge flow as well as piling were simulated numerically with and without rolling resistance of particles. Simulation results were validated on the basis of experimental results. Good agreement of numerical and experimental results in terms of the discharge time and repose angle of the pile was reached simultaneously, when rolling resistance was introduced.     

Feasibility study of particle filters for mobile station receivers

The application of an equalisation method for mobile station terminals using particle filters is presented. To use particle filters for equalisation, a mathematical model is shown which allows the transmitted symbols to be represented as the state of a stochastic system, which can be estimated by particle filters. The authors propose an equaliser structure with particle filters for application in mobile station receivers, especially for GSM/EDGE (global system for mobile communications/enhanced data rate for GSM evolution). Several improvement strategies, which help to obtain better estimation results with a lower number of particles, are discussed. In addition, performance evaluations of the particle filter equaliser for GSM/EDGE are presented.     

Laminar two-dimensional entrance region flow of power-law fluids II

Summary Laminar power-law fluid flow development in a straight channel is obtained by studying a hydrodynamically equivalent model of an appropriate Newtonian fluid.     

Plasma flow crisis and the limiting electron temperature in a vacuum arc in axial magnetic field

The possibility of supersonic motion of cathode plasma in a low-current vacuum arc in an axial magnetic field has been studied. It is shown that an increase in the electron temperature unavoidably leads to a plasma flow crisis, whereby the plasma velocity decreases to the sound velocity. The dependence of the limiting length of a stationary flow on the magnetic field has been studied. The maximum possible electron temperature T _cr in the plasma is determined by the initial ion energy and can be estimated as T _cr ≈ 3T _m, where T _m is the maximum electron temperature in the cathode spot region.