Analysis Of Internal Flows Research Articles

A new mathematical technique for analysis of internal viscoplastic flows through rectangular ducts

The flow of Bingham materials inside rectangular channels is characterized by a plug region located in the central region of the conduit and four dead zones in the vicinity of the corners of the geometry (i.e., the unyielded regions) that grow as the Bingham number is increased. In this paper, a semianalytical technique is presented for solving the flow of Bingham yield-stress materials inside straight rectangular ducts. To capture the topological shapes of the yielded and unyielded regions, a “squircle” mapping approach is proposed and the interfaces between the yielded and unyielded regions are captured based on minimizing the variational formulation for the velocity principle. The nonlinear governing equations are consequently solved using the Ritz method. To find the optimized solution, a genetic algorithm method is implemented, applying bounded constraints and a sufficient number of populations. The presented results are benchmarked against numerical works available in literature, revealing that the presented solution can accurately capture the positions of both the plug and dead regions. The critical Bingham number at which the plug region meets the dead regions is reported for different aspect ratios. The velocity profiles and the friction factor of flow with different Bingham numbers and aspect ratios are investigated in detail. Following this, in the limiting case in which the Bingham number is sufficiently small, an alternative, simpler analytical approach using elliptical mapping is also proposed. The authors believe that the proposed method could be employed as a useful tool to obtain fast, accurate approximate analytical solutions for similar classes of problem.

DIAGNOSTICO SITUACIONAL DA GESTAO DE MATERIAIS PARA A PESQUISA, DESENVOLVIMENTO E INOVAÇÃO DE FITOMEDICAMENTOS EM FARMANGUINHOS

Com uma abordagem inicial que servirá de base para um estudo mais aprofundado, no futuro, sobre a perspectiva do cenário que envolve a gestão de materiais para a pesquisa, desenvolvimento e inovação (PD&I) em fitoterápicos e fitomedicamentos na Fundação Oswaldo Cruz/ Farmanguinhos, este trabalho tem como objetivo elaborar um diagnóstico situacional atual da gestão de materiais

Правовые основы землевладения и землепользования переселенцев в Семиречье в конце XIX – начале XX в.

The relevance of addressing the issue of land management by peasant migrants in the national peripheries of the Russian Empire is associated not only with the need to take into account interethnic and religious relations in the regions and provide a detailed analysis of external and internal migration flows, but also with insufficient study of the topic. Land relations were especially difficult in all Russia’s regions with prevailing nomadic populations: Semirechye (Zhetysu), Lower Volga region, Ciscaucasian steppes, etc. The greatest contribution to the study of the question was made by pre-revolutionary researchers who, as a rule, were government officials obliged to deal with the resettlement (Rumyantsev P. P., Kaufman A. A., Palen K. K., etc.). In the Soviet period, the topic was examined in detail by N. E. Bekmakhanova. Currently, the study of the problem has become actual due to the need to clarify and reassess some of the established past views. Goals. The paper seeks to analyze the legal status of migrant peasants in the region inhabited by nomadic peoples and their land management practices. Materials and Methods. The work involves a wide range of legislative and statistical sources, eyewitness accounts and materials from central archives of Russia, Kazakhstan and Uzbekistan, revealing the complex nature of legal land system definitions of immigrant peasants. Results. During the government-initiated and spontaneous colonization of Semirechye in the late 19th and early 20th centuries, various types of rural peasant settlements ― old-timed, newly emerged and self-willed ones ― were established, which required legal land management regulation. Since administrative agencies in many cases found it difficult to determine legal statuses of peasant lands in Semirechye, the migrants had to solve the problem of land use on their own entering into negotiations with nomadic communities, directly renting land from the latter under different conditions. This made it even more difficult to finally resolve the issue of legal regulation of land tenure and land use. Conclusions. Local administrations – due to the complexity of land relations between immigrants and nomads, poor vision of a complete picture of land management in the region, lack of land for the growing population and the difficulty of conducting Stolypin land management – were able to start collecting information about land management in Semirechye and actually conduct land allocation only in the beginning of the 20th century. The outbreak of World War I and subsequent social upheavals made it impossible to complete the determination of legal foundations of resettlement land management in Semirechye in the pre-revolutionary period.

Numerical and empirical evaluation of a novel building integrated collector storage solar water heater

Abstract Integrated collector storage is a long established simple low cost solar water heater configuration combining the solar collector with a storage tank into a single unit. Previous studies have shown the potential of integrated collector storage solar water heaters to significantly reduce domestic energy requirements for water heating, however challenges still remain to integrate them in roof/facades and ensure appropriate domestic hot water demand. In this article, a novel integrated collector storage solar water heaters is being investigated. The configuration and geometry proposed incorporates an embedded heating element to provide a self-contained domestic hot water system and consider roof integration restriction allowing the unit to be embedded within a structural insulated roofing panel system. The proposed system also utilizes an inlet diffuser designed to reduce the disruption to the stratification within the storage during and following draw-off. This article presents a Computational Fluid Dynamic analysis of internal flows and heat transfer regimes within this new collector configuration and compares its performance against previous developed prototypes using empirical testing. The increased aspect ratio of the new design was shown to significantly alter the heating and cooling characteristics of the collector, both gaining and loosing heat at a greater rate than the original prototype. The computational analysis showed that the collector charges effectively with some stratification. Higher draw-off rates however resulted in higher bulk water outlet temperatures, providing better energy delivery efficiency. The inlet diffuser was also shown to improve the thermal efficiency of the unit overall. The empirical testing shows the improvement in performance of this novel integrated collector storage solar water heaters against previous developed prototypes. The study highlights the need to review the effect of draw-off regime upon the performance of such systems in order to identify optimal regime and control strategy.

A Numerical Study on the Flow Characteristics of Water and Soil Slurry in Pipe

This study described the phenomena of transport and sedimentation of soil slurry flowed in storm sewers from the perspective of numerical analysis. There have been some research cases reviewing the characteristics of flows inside of storm sewers. Most existing researches have performed experiments and analyses based on a flow of single fluid in conduits. However, this study tried to interpret such a flows as a two-phase flow by taking into account soil slurry, and it also tried to deduce results on the change of flow velocity and volume fraction, as well as characteristics of sedimentation to study the tendency of transport and sedimentation inside of the conduits. In addition, it should be necessary to produce theories and analytical basis which can support design criteria for sedimentation inside of conduits based on the analysis of internal flows in storm sewers. Because of difficulties in observing and interpreting two-phase flows made of soil slurry, there have been few studies on this subject, the objective of this study was to examine this part. Accordingly, in case of soil slurry flowed into real manholes, this study reviewed the characteristics of flows generated inside of conduits by reflecting the rate of flow caused by outflow and that of inflow occurred in mixed forms. This study also checked the scope of impact of discharge capacity caused by sedimentation occurred inside of conduits, and improved the already proposed prediction model of critical sediment depth within storm sewers. When comparing with the proposed model, it was confirmed that this new model showed higher correlation ratio. Keywords: Numerical Analysis, Soil Slurry, Transport, Sedimentation, Two-phase Flow, Discharge Capacity

Velocity field measurements in gas phase internal flows by molecular tagging velocimetry

The goal of the present work is to implement Molecular Tagging Velocimetry (MTV) for the analysis of internal gas flows in mini-channels. A MTV experimental setup has been designed. Tagging and detecting steps are respectively insured by a UV laser and a CCD camera coupled to intensified relay optics. A specific channel with 1 × 5 mm2 rectangular cross section has been designed and equipped with integrated temperature sensors along its 20 cm length. It has been manufactured in PEEK (PolyEtherEther-Ketone) and Suprasil® optical windows have been integrated for the tagging access. Image processing allows extraction of velocity profiles for a pressure driven steady flow of argon through this channel. These profiles are compared to the theoretical profiles of laminar flows and the accuracy of the method is discussed. The MTV potential for the analysis of internal gaseous flows is commented on, with a discussion on perspectives for velocity measurement in rarefied flows and direct access to slip velocity at the walls.

Hybrid Reynolds-Average Navier-Stokes and Kinetic Eddy Simulation of External and Internal Flows

thus alleviating the grid-spacing dependency found in other detached eddy simulation and hybrid Reynoldsaveraged Navier–Stokes and large eddy simulation models. Within the hybrid Reynolds-averaged Navier–Stokes andkinetic eddy simulation model, fourdifferent options (a combination of two different blending functions andthe use of realizability constraints to bound the kinetic eddy simulation model parameters) have been evaluated and studied for flows over airfoils (RAE2822, NACA0015) and a turbine vane configuration. Although all four options showed good correlation with the test data, blendingk-!-SST with kinetic eddy simulation using Menter’sk-!-SST F2 function showed better predictions in separated flows than using the baseline k-!-SST model. OST current computational fluid dynamics (CFD) methods used in the simulation and analysis of external and internal flows are based on Reynolds-averaged Navier–Stokes (RANS) approaches, which depend on turbulence-closure models to provide flowfield turbulent variables. Although RANS approaches yield good predictions for attached flowfields, they fail to accurately predict flow structures in separated-flow regions because they resolve only a portion of the turbulence scales of interest. Of course, the ideal approach would be direct numerical simulation (DNS), because the entire range of spatial and temporal scales of turbulence is resolved, but the computational cost of DNS is prohibitive. Another intermediate technique between DNS and RANS has been proposedtoreplaceRANSinsuchcases;thisapproachiscalledlarge eddy simulation (LES). In LES, the contribution of large energy-containing structures and all scales larger than the grid resolution to momentum and energy transfer is computed, and the effect of subgrid unresolved small

Inferring Directional Migration Propensities from the Migration Propensities of Infants in the United States

Beginning with the 2010 decennial census, the U.S. Census Bureau plans to drop its long-form questionnaire and to replace it with the American Community Survey (ACS). The resulting absence of the larger sample provided by the census count will complicate the measurement and analysis of internal migration flows. In addition, the strategy of averaging accumulated samples over time will mix changing migration patterns. The migration question will refer to a one-year time interval instead of the five-year interval used in the censuses between 1960 and 2000, complicating historical comparisons and the production of multiregional projections based on five-year age groups. Consequently, students of territorial mobility increasingly will find it necessary to complement or augment possibly inadequate data collected on migration with estimates obtained by means of “indirect estimation.” A method is presented that allows one to infer age-specific directional migration propensities at the regional level from birthplace-specific infant population data, which approximates infant migration propensities, and from these infers the migration propensities of all other ages. The method is applied to at the nine-division spatial scale.

Numerical simulation of complex 3D compressible viscous flows through rotating blade passage

This paper describes a three-dimensional compressible Navier-Stokes code, which has been developed for analysis of turbocompressor blade rows and other internal flows. Despite numerous numerical techniques and statement that Computational Fluid Dynamics has reached state of the art, issues related to successful simulations represent valuable database of how particular tech?nique behave for a specifie problem. This paper deals with rapid numerical method accurate enough to be used as a design tool. The mathematical model is based on System of Favre averaged Navier-Stokes equations that are written in relative frame of reference, which rotates with constant angular velocity around axis of rotation. The governing equations are solved using finite vol?ume method applied on structured grids. The numerical procedure is based on the explicit multistage Runge-Kutta scheme that is coupled with modem numerical procedures for convergence acceleration. To demonstrate the accuracy of the described numer?ical method developed software is applied to numerical analysis of flow through impeller of axial turbocompressor, and obtained results are compared with available experimental data.

Mise en résonance acoustique d'une cavité par l'instabilité naturelle d'un écoulement généré par injection pariétale

The linear stability analysis of internal flows generated by side injection (Taylor flows) was used to reach the conditions for an acoustic resonance in a simple rectangular cavity. This result establishes a powerful mechanism for destabilising solid propellant motors. This mechanism, which was first discovered through full numerical simulations, can elucidate some of the unstable behaviour of solid propellant motors. The approach followed makes use of fine experimental measurements compared with the linear theory in cases without resonance and with the full numerical results when resonance is established.

Analysis of hydraulic components using computational fluid dynamics models

This paper presents some results obtained during the computational fluid dynamics (CFD) analysis of internal flows inside a hydraulic component, using a scaling technique applied to numerical pre- and post-processing. The main aim of the work is to demonstrate the reduction of computational work needed for a complete analysis of component behaviour over a wide range of operating conditions. This result is achieved through the adoption of a methodology aimed at giving the highest level of generality to a non-dimensional solution, thereby overcoming the two major limitations encountered in the use of CFD in fluid power design: computer resources and time. In the case study, the technique was applied to a hydraulic distributor and computations were performed with a commercial computational fluid dynamics code. The key factor of this technique is the evaluation, for a given distributor opening, of the Reynolds number of the flow in the metering region. Provided that this number is high enough to ensure that the discharge coefficient has reached its asymptotic value, the characterization of the flow by a single non-dimensional numerical run can be shown. The theoretical contents of the analysis of the re-scaling technique, which focuses on the engineering information necessary in component design, are described in detail. The bases for its subsequent application to actual cases are then outlined. Finally, a fairly close correlation between numerical results and experimental data is presented.

Analysis of internal and external energy flows associated with projected process improvements in biomass ethanol production

Possible improvements in biomass ethanol production are decribed involving heat-pumped distillation, steam-cycle heat integration, elimination of seed fermenters, pretreatment heat integration, advanced pretreatment, thermophilic DMC, and incrased carbohydrate yield to 90% of theoretical. Although speculative, a futuristic process incorporating these improvements may be useful for anticipating some features of a technologically mature biomass ethanol process, as well as for comparing ethanol production to more technologically mature energy-conversion processes. Relative to the current state-of-the-art National Renewable Energy Laboratory process design, the futuristic process has 101% higher electricity revenue, 31% hgiher ethanol revenue, and 35–39% higher overall revenue depending on the assumed ethanol value. The overall first-law thermodynamic efficiency is 43% for the current NREL design and 59% for the futuristic process. A general consideration of the costs associated with the process improvements examined indicates that: 1. Elimination of seed reactors, advanced pretreatment, and thermophilic DMC all have large potential cost reductions independent of their benefits with respect to increased surplus electricity; 2. Steam cycle improvements and pretreatment heat integration are expected to have modest cost benefits that are dependent on increased electricity revenues; and 3. The relative cost of heat-pumped distillation depends on scale, capital recovery, and electricity value, but is generally similar to the already low cost of conventional distillation provided that the fermentation broth has a reasonably high ethanol concentration.

Finite element analysis of internal flows with heat transfer

This paper presents a finite element-based model for the prediction of 2-D and 3-D internal flow problems. The Eulerian velocity correction method is used which can render a fast finite element code comparable with the finite difference methods. Nine different models for turbulent flows are incorporated in the code. A modified wall function approach for solving the energy equation with high Reynolds number models is presented for the first time. This is an extension of the wall function approach of Benim and Zinser and the method is insensitive to initial approximation. The performance of the nine turbulent models is evaluated by solving flow through pipes. The code is used to predict various internal flows such as flow in the diffuser and flow in a ribbed channel. The same Eulerian velocity correction method is extended to predict the 3-D laminar flows in various ducts. The steady state results have been compared with benchmark solutions and the agreement appears to be good.

Self-selection and internal migration in the United States

Within the conceptual framework of the Roy model, this paper provides an empirical analysis of internal migration flows using data from the National Longitudinal Survey of Youth. The theoretical approach highlights regional differences in the returns to skills: regions that pay higher returns to skills attract more skilled workers than regions that pay lower returns. Our empirical results suggest that interstate differences in the returns to skills are a major determinant of both the size and skill composition of internal migration flows. Persons whose skills are most mismatched with the reward structure offered by their current state of residence are the persons most likely to leave that state, and these persons tend to relocate in states which offer higher rewards for their particular skills.

A Note on Outflow Boundary Conditions for the Finite Element Analysis of Internal Viscous Flows with Heat Transfer.

Outflow boundary conditions have been examined for the finite element analysis of internal viscous flow problems. As a test problem, the combination of Poiseuille flow and Benard-Rayleigh convection in a two-dimensional duct has been chosen. Using the test problem, two types of conditions are tested : (A) vanishing of a normal gradient of a quantity and (B) vanishing of a linearized convective derivative. Condition (A) is often used in the finite element analysis of internal fluid flows. In the present test case, it has been found that condition (B) yields better results, showing little reflection of outgoing waves back into the computational domain. In the last part of the paper, a generalized method for including the outflow boundary condition of type (B) into the finite element formulation of Navier-Stokes equations is shown.

Numerical analysis of three-dimensional viscous internal flows

A 3-D Navier-Stokes code has been developed for analysis of turbomachinery blade rows and other internal flows. The Navier-Stokes equations are written in a Cartesian coordinate system rotating about the x-axis, and then mapped to a general body-fitted coordinate system. Streamwise viscous terms are neglected using the thin-layer assumption, and turbulence effects are modeled using the Baldwin-Lomax turbulence model. The equations are discretized using finite differences on stacked C-type grids and are solved using a multistage Runge-Kutta algorithm with a spatially-varying time step and implicit residual smoothing. Calculations have been made of a horseshoe vortex formed in front of a flat plate with a round leading edge standing in a turbulent endwall boundary layer. Comparisons are made with experimental data taken by Eckerle and Langston for a circular cylinder under similar conditions. Computer and measured results are compared in terms of endwall flow visualization pictures and total pressure loss contours and vector plots on the symmetry plane. Calculated details of the primary vortex show excellent agreement with the experimental data. The calculations also show a small secondary vortex not seen experimentally.

Channel and Tube Flows with Surface Mass Transfer and Velocity Slip

An analysis of internal flows with surface mass transfer is performed in which account is taken of velocity slip at the surface of the porous bounding wall. The solutions for channel and tube flows reveal a variety of interesting effects of velocity slip, which depend upon whether fluid is injected or withdrawn at the bounding wall and upon the sign of the streamwise pressure gradient. For example, relative to the situation in which there is no slip, the streamwise pressure gradient may either increase or decrease in the presence of slip and may even undergo a change of sign.