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The implementation of an integral transition model in a parallel unstructured computational fluid dynamics code is described. In particular, an algorithm for gathering the nonlocal boundary, layer values (momentum thickness and shape factor) from parallel distributed computational domains is presented. Transition modeling results are presented for a flat plate and for a low pressure turbine, covering a large variation of Reynolds numbers, Mach numbers, turbulence intensities, and incidence angles. Contrary to fully turbulent simulations, transitional predictions are in very good agreement with measurements. Furthermore, the computational overhead of transitional simulations is only 7% for one multigrid cycle. [DOI: 10.1115/1.2987238]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.chb.2008.07.010 Byline: Sarah Manlove, Ard W. Lazonder, Ton de Jong Abstract: This paper looks across three experimental studies that examined supports designed to assist high-school students (age 15-19) with cognitive regulation of their physics inquiry learning efforts in a technology-enhanced learning environment called Co-Lab. Cognitive regulation involves the recursive processes of planning, monitoring, and evaluation during learning, and is generally thought to enhance learning gains for students. The research synthesis described in this paper examined the usage effects of a support tool called the process coordinator (PC) on learning outcomes. This tool incorporated goal-lists, hints, prompts, cues, and templates to support the cognitive regulation skills of students during a fluid dynamics task. Students were asked to produce two learning outcomes of their investigations: system dynamics models and lab reports. Results from the three studies indicated trends in frequent use of the PC for planning activities, but low usage for monitoring and evaluation. Correlational analysis revealed two trends with regard to how these regulative activities impacted learning outcomes. First, consistent positive correlations were apparent between regulative activities and lab report scores of students and second, consistent negative correlations between the use of supports and model quality scores. Trends with regard to how task complexity, time, and student prior experience impacted these findings are also presented with suggestions for future research. Author Affiliation: University of Twente, Faculty of Behavioral Sciences, Department of Instructional Technology, P.O. Box 217, 7500 AE Enschede, The Netherlands

Butterfly valve performance coefficients are necessary for predicting the required torque necessary to operate the valve along with other essential parameters necessary for ensuring the safe operation. The availability of performance coefficients for compressible flow is limited, and experimental testing can be cost prohibitive. The capability of using computational fluid dynamics is a test to determine its viability for determining performance coefficients. The flow field, resultant force, and aerodynamic torque on a symmetric disk butterfly valve are studied computationally at disk positions 45 deg and 70 deg over a range of operating pressures. The range of pressure ratios was chosen to include subsonic and supersonic flow states. The flow fields were predicted using the k-epsilon renormalization group theory (RNG) turbulence model. The computational results were obtained using CFX 10 and were performed on an set ALTIX 330. The flow field is illustrated using velocity contours colored by a Mach number, and the effects of the disk position and pressure ratio are illustrated using disk pressure profiles. The computational predictions for the aerodynamic torque coefficients are compared to test data at both 45 deg and 70 deg. A simplistic model used to predict the resultant force acting on the disk is compared against the computational results to obtain a better understanding of the resultant force trend throughout the stroke. The numerical results were generally in good agreement with test data, although a few disparities existed. [DOI: 10.111511.2891929]

A moving-deforming grid study was carried out using a commercial computational fluid dynamics (CFD) solver, FLUENT(R) 6.2.16. The goal was to quantify the level of mixing of a lower-viscosity additive (at a mass concentration below 10%) into a higher-viscosity process fluid for a large-scale metering gear pump configuration typical in plastics manufacturing. Second-order upwinding and bounded central differencing schemes were used to reduce numerical diffusion. A maximum solver progression rate of 0.0003 revolutions per time step was required for an accurate solution. Fluid properties, additive feed arrangement, pump scale, and pump speed were systematically studied for their effects on mixing. For each additive feed arrangement studied, the additive was fed in individual stream(s) into the pump-intake. Pump intake additive variability, in terms of coefficient of spatial variation (COV), was >300% for all cases. The model indicated that the pump discharge additive COV ranged from 45% for a single centerline additive feed stream to 5.5% for multiple additive feed streams. It was found that viscous heating and thermal/shear-thinning characteristics in the process fluid slightly improved mixing, reducing the outlet COV to 3.2% for the multiple feed-stream case. The outlet COV fell to 2.0% for a half-scale arrangement with similar physics. Lastly, it was found that if the smaller unit's speed were halved, the outlet COV was reduced to 1.5%. [DOI: 10.1115/1.2436577]

Computational fluid dynamics (CFD) model simulations of urban boundary layers have improved in speed and accuracy so that they are useful in assisting in planning emergency response activities related to releases of chemical or biological agents into the atmosphere in large cities such as New York, New York. In this paper, five CFD models [CFD-Urban, Finite Element Flow (FEFLO), Finite Element Model in 3D and Massively-Parallel version (FEM3MP), FLACS, and FLUENT-Environmental Protection Agency (FLUENT-EPA)] have been applied to the same 3D building data and geographic domain in Manhattan, using approximately the same wind input conditions. Wind flow observations are available from the Madison Square Garden 2005 (MSG05) field experiment. Plots of the CFD models' simulations and the observations of near-surface wind fields lead to the qualitative conclusion that the models generally agree with each other and with field observations over most parts of the computational domain, within typical atmospheric uncertainties of a factor of 2. The results are useful to emergency responders, suggesting, for example, that transport of a release at street level in a large city could extend for a few blocks in the upwind and crosswind directions. There are still key differences among the models for certain parts of the domain. Further examination of the differences among the models and the observations are necessary in order to understand the causal relationships.

An improved method for simulating frequency-dependent friction in laminar pipe flow using the method of characteristics is proposed. It has a higher computational efficiency than previous methods while retaining a high accuracy. By lumping the frequency-dependent friction at the ends of the pipeline, the computational efficiency can be improved further, at the expense of a slight reduction in accuracy. The technique is also applied to the transmission line method and found to give a significant improvement in accuracy over previous methods, while retaining a very high computational efficiency. [DOI: 10.1115/1.2361320]

Applications of fluid dynamics models in traffic equilibrium and pricing problem are analyzed. Its application in supply chain management is also examined.

The use of green features in building design not only improves the environmental quality, but also reduces the consumption of non-renewable energy used in active control of indoor environment. Larger [...]

With rapid advances in micro-device fabrication, computational techniques, and diagnostic tools, there is a significant interest in applying micro-scale fluid dynamics and heat transfer to flow control, flight vehicle protection, and thermal management. Utilizing energy transfer associated with phase change, multiphase systems offer many new opportunities. To elucidate the main scientific issues and technical implications, recent research addressing the interplay between capillarity, moving boundaries, fluid dynamics, heat transfer, and phase change of micro-scale multiphase systems is reviewed. The parametric variations in contact angle, surface tension, impact velocity, and liquid viscosity related to drop impingement and heat transfer are discussed.

The inverse design method is applied to a design problem of transonic wing planform and section shape design.

A computation structural dynamics and computational fluid dynamics method for simulating and predicting flutter is presented.

Fluid dynamics is discussed in the context of advances in aerodynamics.

An efficient computational method was developed to define aerodynamic loads on maneuvering flexible flight vehicles. It is based on the conventional Navier-Stokers/Euler code, and the computational fluid dynamics (CFD) code was supplemented with a modal structural model. Normal modes, used for the representation of the structure, were accurate, producing an interface between the CFD and the structure.

Techniques used to determine F/A-18E wind-tunnel lift and drag characteristics to generate aircraft performance predictions are described. High-fidelity models, comprehensive test programs and integration of computational fluid dynamics ensured first-time quality test results. Good agreement between wind-tunnel and flight results enable the performance flight evaluation plan to be reduced by 60 flights.

A new chimera-domain decomposition procedure is presented, based on a new cut-past algorithm for optimal mesh interface and a two stage search method for donor cell identification. Interpolation points are situated away from solid walls, and errors that may arise from interpolation in stiff gradient regions can be reduced.

Total cavopulmonary connection is a surgical process for treating complex congenital malformations of the right heart. A three-dimensional model for this connection is shown based on in vivo measurements conducted by magnetic resonance. The model was developed through computational fluid dynamics methods, namely, the finite element method. Findings revealed that the flow distribution between the lungs is slightly influenced by the shape of inlet velocity profiles, while it is affected by various pressure levels to a larger extent.

Computational fluid dynamics (CFD) researchers aim to accurately predict aerodynamic forces from numerical simulations. A momentum balance approach has developed a system of integrals reducing the task of force computation to the integration of certain flow parameters in a crossflow plane. The decomposition of the drag can be used to formulate methods to evaluate drag accurately.

Extragalactic jets were first studied and discovered by radio astronomers as they worked with extended radio sources. The combination of disks and jets is thought to be the crucial element in unification models for active galactic nuclei (AGNs). Propagation and acceleration conditions of jets, along with the aspect ratio of the disk/jet geometry as it relates to the observer, shape morphologies of AGNs. The very complex phenomenological models involve elements of various theories in a very nonlinear combination and in conditions not easy to reproduce in fluid experiments or laboratory plasma. Some advanced analytical/numerical methods have been used and a global scenario confirmed, but no complete physical interpretation exists. Results which have come from jet modeling have been summarized, with emphasis on limitations of available models and possibility of new developments.

A new design method for reducing drag through the design of natural laminar flow (NLF) airfoils is presented. The method uses proven computational fluid dynamics (CFD) analysis, combined with a new target pressure design method. Its main features are a compressible linear stability analysis code which calculates the N-factors and its ability to calculate a target N-factor distribution.

There are many physical parameters that influence the thermal condition of a hydro-dynamic journal bearing. This remains the case even when appropriate nondimensionalization procedures have been applied. However, two dimensionless parameters are particularly useful, since they embody lubricant shearing, convection, conduction and viscosity temperature variation. In this paper, these parameters are varied to obtain design charts for the maximum bearing shell and journal temperatures. Computational fluid dynamics (CFD) techniques are used in this process. They are applied to a generic two-axial groove circular bearing having a section of journal that extends beyond the width of the shell. The results demonstrate the usefulness of the charts through example design studies.

The flow of Newtonian liquids through a pipe system comprising of a series of abrupt expansions and contractions has been studied using several magnetic resonance imaging (MRI) techniques, and also by computational fluid dynamics. Agreement between those results validates the assumptions inherent to the computational calculation and gives confidence to extend the work to more complex geometries and more complex fluids, wherein the advantages of MRI (utility in opaque fluids and noninvasiveness) are unique. The fluid in the expansion-contraction system exhibits a broad distribution of velocities and, therefore, presents peculiar challenges to the measurement technique. The MRI protocols employed were a two-dimensional tagging technique, for rapid flow field visualisation, and three-dimensional echo-planar and gradient-echo techniques, for flow field quantification (velocimetry). The computational work was performed using the FIDAP package to solve the Navier-Stokes equations. The particular choice of parameters for both MRI and computational fluid dynamics, which affect the results and their agreement, have been addressed.

A general review of Computational Fluid Dynamics (CFD) applications in the automotive industry is presented. CFD has come a long way in influencing the design of automotive components due to continuing advances in computer hardware and software as well as advances in the numerical techniques to solve the equations of fluid flow. The automotive industry's interest in CFD applications stems from its ability to improve automotive design and to reduce product cost and cycle time. We are able to utilize CFD more and more in day-to-day automotive design, and we can expect better conditions for CFD applications in the coming years. CFD applications in the automotive industry are as numerous as are the codes available for the purpose. Applications range from system level (e.g., exterior aerodynamics) to component level (e.g., disk brake cooling). The physics involved cover a wide range of flow regimes (i.e., incompressible, compressible, laminar, turbulent, unsteady, steady, subsonic and transonic flows). Most of the applications fall in the incompressible range and most are turbulent flows. Although most of the flows encountered are unsteady in nature, a majority of them can be approximated as steady cases. The challenge today is to be able to simulate accurately some very complex thermo-fluids phenomena, and to be able to get CFD results fast, in order to effectively apply them in the 'dynamic' design environment of frequent design changes. The key is to utilize CFD in the early design phases so that design changes and fix-ups later are minimized. Proper use of CFD early, helps to significantly reduce prototyping needs and consequently, reduce cost and cycle time.

Computational fluid dynamics (CFD) analyze the aerodynamic loads that cause tail buffet on the F/A-18 fighter aircraft and give time-accurate solutions with and without the leading-edge extension (LEX) fence. These results show the ability of the aircraft to fly at high-angle-of-attack. The surface pressure distributions yield the vertical tail root bending moment and side force time histories. The CFD solution predicts the unsteady rms pressure coefficient, the peak power and the effect of LEX fence on these quantities.

A new kind of equipment for the sequential production of mm-sized solid spherical shells was invented. This device employs liquid-liquid gas systems and is composed of a cylindrical vessel which houses two types of immiscible liquids, and a gas injection port, placed at the middle of the vessel's bottom. Solid spherical shells are developed by solidifying the rising liquid spherical shells, produced sequentially at the horizontal interface between two immiscible liquids.

Eddy shedding and related biological activity are common features of oceanic eddy formation found in oceanic islands such as the tropical island of Aldabra located in the South Equatorial Current of the Indian Ocean. The occurrence of eddy shedding is in accordance with non-rotating fluid theory and the Reynolds number, leading to the hypothesis that islands at high latitudes exhibit eddy thresholds similar to those predicted in laboratories. While shedding frequency does not correlate indefinitely with the Reynolds number, it does conform with theoretical predictions of Strouhal numbers.

The physical laws governing parachute motion and the applications of these analyses for designing parachutes using numerical and computational methods are discussed. The aerodynamics of the unfurling of the parachute cloth and the movement of the canopy is analyzed.

The present study assesses the ability of the k-Epsilon turbulence model to calculate the flow inside gas turbine combustors. Results of calculations using a cylindrical system of coordinates, hybrid differencing, and a mesh with about 40,000 nodes are compared with velocity measurements of the flow inside a perspex model of can-type gas turbine combustor. The larger discrepancies between measurements and predictions were found in the primary region. The complexity of the flow near the primary jet impingement led to underprediction of the maximum negative axial velocity and turbulence kinetic energy by about 35 and 20 percent, respectively. The calculated results exhibited higher levels of momentum diffusion compared to the experiments and did not show the two contrarotating vortices created between the primary jets; no qualitative agreement with the azimuthal velocity downstream of the primary jets could be achieved. Despite these deficiencies, the model gave acceptable results in other regions of the combustor and correct prediction of the main features of the combustor flow was possible.

Computational fluid dynamics is used in the analysis of the effectiveness of a tangential slot blowing concept for the generation of lateral control forces on an aircraft forebody. Multiple-zone, thin-layer Navier-stokes codes are used in the computation of the flow of a fighter forebody. An actuator plane is used to model the tangential slot blowing. The positioning of the slot near the nose of the aircraft increases the efficiency of the system. However, the length and circumferential location of the slot are not of prime importance.

The modeled configuration of three-dimensional thin-layer Navier-stokes computations for F/A-18 configuration includes a precise surface representation of the fuselage, leading-edge extension (LEX) and wing, with or without the leading wind deflection. The computational flowfield domain around the subject configuration is decomposed using the multiblock structured grid strategy. The compressible Navier-stokes equations with an upwind-biased, flux difference splitting approach is solved by an algorithm, and the steady state solutions determined.

The pressure disturbances at near- and mid-fields caused by supersonic flight is studied using computational fluid dynamics in conjunction with the quasilinear theory. Wind-tunnel tests are carried out on three sonic-boom models at different freestream Mach numbers to determine the factors that determine the structure of the sonic boom. Results indicate that the sonic boom structure is affected by the sting of the wind-tunnel model.

A study was conducted to examine the problem of incompressible fluid laminar flow over a wavy surface similar to a monolayer of vascular endothelial cells. Numerical calculations and linear pertubation theory are applied to the study. The calculations describe arterial flow conditions close to the wall at any point in time and includes details of the velocity field. Results show qualitative similarity between surface pressure and shear stress distributions when linear theory and computations are applied. However, variations occur as surface undulation amplitude is increased.

Computational fluid dynamics (CFD) is now regarded by the aerospace industry as a reliable tool for analyzing the different problems encountered in aerospace vehicle design and manufacture. Many companies are investing substantial research and development resources on CFD. They believe CFD can shorten the design cycle process and supply reliable analyses and data more effectively than traditional methods.

Many modern sulfur recovery unit process waste heat recovery exchangers operate in high-temperature environments. These exchangers are associated with the thermal reactor system where the tube-sheet-tube-ferrule assemblies are exposed to gasses at temperatures approaching 3000[degress]F. Because sulfur compounds are present in the process gas, the carbon steel tube sheet and tubes in the assembly will be deteriorated by sulfidation as the operating metal temperature rises above 600[degrees]F. Ferrule systems are used to protect the carbon steel from exposure to excessive temperatures. The temperature distribution in the steel tube-sheet-tube-ferrule system is affected by process gas flow and heat transfer through the assembly. Rather than depend on 'assumed' heat transfer coefficients and fluid flow distribution, a computational fluid dynamics investigation was conducted to study the flow fields and heat transfer in the tube-sheet assembly. It was found that the configuration of the ferrule installation has a large influence on the temperature distribution in the steel materials and, therefore, the possible sulfidation of the carbon steel parts. [DOI: 10.1115/1.2716436]

The article discusses about the new developments that could help computational fluid dynamics (CFD) gain popularity.

A three-dimensional, viscous, computational fluid dynamics (CFD) analysis was undertaken of the exhaust flow linked to the auxiliary power unit (APU) of an advanced fighter aircraft. The aim was to examine the impact of the surge line relocation on the APU exhaust flow. The results of previous APU exhaust impingement analyses were corroborated, and the CFD investigation reduced overall risk linked to proposed design modifications.