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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]

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]

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]

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.

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.

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.

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.

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.

Accurate computational fluid dynamic (CFD) studies of aircraft must consider ways of solving the fluid dynamic equations. A computational simulation was performed for the aircraft configuration of the F-22. The Reynolds number was based on reference length c of the wing root chord of the model, and the wind-tunnel test was performed ona 0.10 scale model without stores. The comparison of surface pressure on the upper surface showed good qualitative agreement between experiment and computations.

Byline: Spyros Kamnis, Sai Gu A Computational Fluid Dynamic (CFD) model is developed to examine the heat transfer process through the water-cooling mechanism in a High Velocity Oxygen Fuel (HVOF) thermal spraying system. The water-cooling configuration is composed of a series of discrete holes through the copper-made thermal spraying gun. Unstructured grid is employed for both liquid and solid regions and the water-cooling model is fully integrated with the gas flow dynamics where combustion, turbulent flow and free jet expansion are included. The numerical results indicate that the water flow direction has noticeable influence on the cooling efficiency due to the variation of heat capacity of water and the current cooling mechanism has no noticeable effect on the gas flow dynamics within the thermal spraying gun.

It is well known that lean premixed combustion systems potentially offer better emissions performance than conventional non-premixed designs. However, premixed combustion systems are more susceptible to combustion instabilities than non-premixed systems. Combustion instabilities (large-scale oscillations in heat release and pressure) have a deleterious effect on equipment, and also tend to decrease combustion efficiency. Designing out combustion instabilities is a difficult process and, particularly if many large-scale experiments are required, also very costly. Computational fluid dynamics (CFD) is now an established design tool in many areas of gas turbine design. However, its accuracy in the prediction of combustion instabilities is not yet proven. Unsteady heat release will generally be coupled to unsteady flow conditions within the combustor. In principle, computational fluid dynamics should be capable of modeling this coupled process. The present work assesses the ability of CFD to model self-excited combustion instabilities occurring within a model combustor. The accuracy of CFD in predicting both the onset and the nature of the instability is reported. [DOI: 10.1115/1.1362662]

Suspensions of swimming algal cells form intricate mottled patterns that are governed by a complex interplay between light, gravity and fluid dynamics. The patterns (pictured) change with shifting lighting conditions, [...]

Suitable techniques to transfer information between nonlinear computational fluid dynamics (CFD) and computational structural dynamics (CSD) grids were identified and evaluated. Such data transfer is essential in computational aeroelasticity and methods need to provide smooth and accurate transfer.

The numerical model of parachute inflation involves a computational fluid dynamics code, which was coupled with the structural dynamics code. The system was developed to test the space shuttle orbiter landing/deceleration parachute system. Martin-Baker is developing a system for Cassini-Huygens probe, which will land on Saturn's moon Titan.