Numerical Simulations (numerical + simulation)

Distribution by Scientific Domains
Distribution within Engineering

Kinds of Numerical Simulations

  • direct numerical simulation
  • three-dimensional numerical simulation

  • Terms modified by Numerical Simulations

  • numerical simulation model
  • numerical simulation result
  • numerical simulation study

  • Selected Abstracts

    Regular Arrays of Microdisk Electrodes: Numerical Simulation as an Optimizing Tool to Maximize the Current Response and Minimize the Electrode Area Used

    ELECTROANALYSIS, Issue 23 2006
    Abstract Microdisk electrode arrays constitute an interesting tool for electroanalysis and electrocatalysis due to their increased sensitivity and excellent limits of detection. We first demonstrate that a 2-dimensional simulation based on the diffusion domain approximation can be used to simulate the response of such electrochemical systems and therefore improve their design and fabrication process. Second, we report data showing the peak current response for arrays at three typically employed voltage scan rate as a function of the number of disks per unit area and their radii. [source]

    Physical and Numerical Simulation of Cold Rolling of an AlFeSi Alloy in Consideration of Static Recovery,

    Christoph Heering
    The influence of static recovery on the yield stress of AA8079 was investigated in lab-scale cold rolling experiments. The yield stress of AA8079 in the cold rolling process is affected by static recovery, but the softening caused by static recovery is completely compensated in the subsequent cold rolling pass. Thus, the effect of static recovery on the yield stress of the final product is of minor importance. For the TPM, the kinetics of static recovery of the AlFeSi alloy AA8079 were determined for different temperatures and strain rates. The measured softening kinetics were then implemented in the physically based flow stress model 3IVM+. This flow stress model was extended with an empirical approach for static recovery to enable the through-process modeling of cold-rolled aluminum in consideration of static recovery. Future work will focus on physically based modeling of static recovery without using empirical approaches. [source]

    Numerical Simulation of the Application of NiTi Alloys in Medical Technologies

    Daniel Christ
    Shape memory alloys are nowadays already established as a material which is able to solve exceptional tasks in practical applications. Particularly, its utilization in the field of medical technologies increases steadily. For example micro tools (staple, catheters) and implants (coronary stents) are made out of Nickel-Titanium well known as a basic shape memory alloy. Apart from the advantages like the avoidance of auxiliary components and joints in the system and to utilize the high volume specific work of shape memory alloys, NiTi alloys exhibit a good biocompatibility. This property is necessary with regard to either permanent or temporary implants. To optimize the use of NiTi alloys in the scope of medical technologies, the support of the development of applicable tools by numerical simulations is highly recommended. However the complex material behaviour containing a profoundly thermomechanical coupling poses indeed a big challenge to the material modeling and its implementation into a finite element code. Particularly, the material model proposed by Helm [1] proves to be a firm model containing the most common properties of shape memory alloys, as the pseudoelasticity, the shape memory effect and the two-way effect. In the present contribution the FE modelling of a medical staple used in foot surgery is presented by considering the model of Helm which was investigated by the authors to improve its performance in the finite element method [2]. The foot staple, produced by a group of members of the SFB 459 which is funded by the DFG, avails the shape memory effect to excite the desired clamping effect [3]. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Towards High Order Numerical Simulation of Aeolian Tones

    Bernhard Müller
    Strictly stable high order finite difference operators have been applied to the compressible Navier-Stokes equations in perturbation form for low Mach number computational aeroacoustics. Aeolian tones generated by vortex shedding from a circular cylinder have been simulated. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Numerical Simulation of Fluid Flow and Enzyme Catalysed Substrate Conversion in a Packed-bed Enzyme Reactor

    Ö. Özmutlu M. Sc.
    This numerical study evaluates the momentum and mass transfer in an immobilized enzyme reactor. The simulation gives detailed information of the local substrate and product concentrations with respect to external and internal transport limitations. The flow field characterization of the system makes it possible to understand fluid mechanical properties and its importance on transport processes. With the obtained data it is also possible to detect zones of high, low and latent enzymatic activity and to determine whether the conversion is limited due to mass transfer or reaction resistances. [source]

    Numerical Simulation of Pollution Dispersion over Real Terrain

    k Bene
    The paper presents a mathematical and numerical investigation of the atmospheric boundary layer (ABL) flow over coal depot. Two mathematical models have been mentioned based upon: 1) the RANS equations in the conservative form and 2) the Boussinesq approximation of RANS equations in the non,conservative form, both formulated for an incompressible flow with a simple algebraic turbulence closure and given stationary boundary conditions. Also pollution dispersion of passive pollutants has been considered. [source]

    Modeling and Numerical Simulation of Cavitation for Compressible Liquid Flow

    A. Berg
    A method for the numerical simulation of cavitation phenomena based on the thermodynamic properties of liquid and steam is described. Thereby, a homogeneous cavitation model using a fully compressible discretization technique is considered. The ability of the scheme is proven by numerical experiments. [source]

    Behaviour of a Moving Droplet under Electrowetting Actuation: Numerical Simulation

    K. Mohseni
    Abstract Numerical simulation of droplet transport in microchannels under electrostatic actuation is investigated. Volume-of-Fluid (VOF) technique is employed, in which electrowetting effects are implemented through Lippmann's relation in the form of modified contact angles at the boundary. A velocity of about 35 mm/s is achieved with the actuation of 40 V. The droplet flow under electrowetting actuation is characterized for the majority of the process parameters such as actuation voltage, channel dimension, electrode size, and resultant velocity. On étudie la simulation numérique du transport de gouttelettes dans des microcanaux lors d'une actuation électrostatique. On emploie la technique des volumes de fluide (VOF), dans laquelle les effets de l'électromouillage sont introduits dans la relation de Lippmann sous la forme d'angles de contact modifiés à la frontière. Une vitesse d'environ 35 mm/s est atteinte avec une actuation de 40 V. L'écoulement des gouttelettes dans l'actuation électromouillante est caractérisé pour la majorité des paramètres de procédé, tels que le voltage d'actuation, la dimension des canaux, la taille des électrodes et la vitesse résultante. [source]

    Numerical Simulation of Thrombus Aspiration in Two Realistic Models of Catheter Tips

    ARTIFICIAL ORGANS, Issue 4 2010
    Giancarlo Pennati
    Abstract Thrombus aspiration catheters are devices used to remove a blood clot from a vessel, usually prior to angioplasty or stent implantation. However, in vitro results showed that the use of different commercial devices could produce very different thrombus removals, suggesting a primary dependence on the distal tip configuration of the catheter. A computational methodology based on realistic catheter tip modeling was developed to investigate the factors affecting the thrombus suction. Two different designs were considered, either with a single central lumen or a combination of central and side holes. First, steady-state aspiration of distilled water from a reservoir was simulated and compared with experimental tests. Subsequently, the aspiration of a totally occlusive thrombus, modeled as a high viscous fluid, was simulated solving a complex two-phase (blood and thrombus) problem. In particular, the benefit of additional openings was investigated. Good matching between the steady-state experimental and numerically simulated hydraulic behaviors allowed a validation of the numerical models. Numerical results of thrombus aspiration showed that the catheter with central and side holes had a worse performance if compared with the single central lumen catheter. Indeed, the inlets in contact with both blood and thrombus preferentially aspirate blood due to its much lower viscosity. This effect hindered the aspiration of thrombus. The amount of aspirated thrombus highly depends on the complex, two-phase fluid dynamics occurring across the catheter tips. Results suggested that location of additional holes is crucial in the catheter aspiration performance. [source]

    Numerical Simulation of Hemodynamic Changes During Beating-heart Surgery: Analysis of the Effects of Cardiac Position Alteration in an Animal Model

    ARTIFICIAL ORGANS, Issue 1 2007
    Gianfranco Ferrari
    Abstract:, Hemodynamic instability, mostly due to vertical lifting of the heart, is usually observed during beating-heart surgical procedures. However, some hemodynamic parameters, such as coronary blood flow, are not routinely measured. A digital computer model of the circulation able to simulate and analyze the effects of heart lifting and the Trendelenburg maneuver, and thus supply detailed hemodynamic information to the clinicians would provide a useful analytical tool. A lumped parameters model of the circulation was applied to both ,-blocked and not ,-blocked pigs. The results confirmed a drop of cardiac output and coronary flow during heart lifting and a rise of both variables after the Trendelenburg maneuver for ,-blocked animals. In not ,-blocked pigs, the analysis was more complex but the model reproduced experimental data and permitted coronary flow to be estimated. These results showed the feasibility of numerical simulation for specific circulatory conditions encountered during beating-heart surgery. [source]

    Direct Numerical Simulation of Dense Gas-Solid Two-Phase Flows

    Y. Zhulin
    Based on Newton's law and the classical physical laws, Eulerian and Lagrangian methods are respectively used to deal with gas-field and discrete particles. The three-dimensional viscid air-field and three-dimensional discrete particle field are solved in each time step ,t. Collision and friction between individual particles are taken into account when establishing the mathematical models, including individual particle diameter, density, stiffness and friction coefficient. Particles mixing in ball mills, particles dropping from hoppers, and particles fluidizing in fluidized beds are used as examples of the simulations. Selected simulated results are compared to experimental results. [source]

    Numerical Simulation of Absorbing CO2 with Ionic Liquids

    X. Wang
    Abstract Although separating CO2 from flue gas with ionic liquids has been regarded as a new and effective method, the mass transfer properties of CO2 absorption in these solvents have not been researched. In this paper, a coupled computational fluid dynamic (CFD) model and population balance model (PBM) was applied to study the mass transfer properties for capturing CO2 with ionic liquids solvents. The numerical simulation was performed using the Fluent code. Considering the unique properties of ionic liquids, the Eulerian-Eulerian two-flow model with a new drag coefficient correlation was employed for the gas-liquid fluid dynamic simulation. The gas holdup, interfacial area, and bubble size distribution in the bubble column reactor were predicted. The mass transfer coefficients were estimated with Higbie's penetration model. Furthermore, the velocity field and pressure field in the reactor were also predicted in this paper. [source]

    Numerical Simulation of the Hydrodynamics of Gas/Solid Two-Phase Flow in a Circulating Fluidized Bed with Different Inlet Configurations

    Y. Li
    Abstract The gas/solid flow characteristics in a circulating fluidized bed with two different inlet configurations were investigated by numerical simulation based on an Eulerian approach. In order to describe the interaction between the gas phase and the solid phase and the influence of the solid phase on the gas turbulence, a source term formulation with a more reasonable physical meaning was introduced. The simulation results were validated by the experimental data; then, the model was employed to examine the effect of the inlet configuration on the gas and solid feeding. The simulation results showed that, using the side feeding system, the distributions of solid flow and concentration were highly variable both over the column cross-section and along the column height. However, such variations can be improved by using the elbow inlet system where the gas and solid are fed from the bottom. [source]

    Filtration of Colloidal Suspensions , MRI Investigation and Numerical Simulation

    A. Erk
    Abstract The principle mechanisms of solid-liquid separation processes are sedimentation and filtration, both including the formation and compression of a liquid-saturated bulk. The compressive properties of the bulk determine the operating parameters of solid-liquid separation devices and the achievable separation results. Information about the solids volume fraction of the bulk is essential for a better understanding of the physical mechanisms and precise modeling. A numerical model for the calculation of the local solids volume fraction during formation and compression of filter cakes and sediments was developed. The calculated results are compared with experimental NMR data. [source]

    Carbon Long Fiber Reinforced Aluminum Matrix Composites , Parameter Studies and Numerical Simulations of the Infiltration Process,

    Heiko Ballmes
    Within this work, the development of a cost efficient and reliable production technique for infiltrating carbon fibers with aluminum using a conventional cold chamber die casting machine is reported. Results are presented that demonstrate the large potential of pressure die casting as a low cost manufacturing process for carbon fiber reinforced aluminum matrix composites. The influence of process parameters on the infiltration behaviour is investigated and compared to results gained by numerical simulation. [source]

    Turbulent Dynamics of Beryllium Seeded Plasmas at the Edge of Tokamaks

    R.V. Shurygin
    Abstract Numerical simulation of turbulent MHD dynamics of beryllium seeded plasmas at the edge of tokamaks is performed. The model is based on the 4-fluid {,, n, pe, pi } reduced nonlinear Braginsky's MHD equations. Neutral hydrogen flow from the wall is described with a diffusion model. Beryllium line radiation is taken into consideration. The Be ion distribution over ionization states is calculated using the reduced model. Electron impact ionization, three body, photo- and dielectronic recombination and charge-exchange with neutral hydrogen are taken into account. Coronal equilibrium is not supposed. Simulations are performed for T-10 parameters. Radial distributions of averaged temperatures and their fluctuation levels, species flows, impurity radiation power, and impurity ions concentrations are obtained as functions of the Be concentration at the wall. The impurity radiation is shown to act on the turbulent oscillation level significantly if the total Be concentration at the wall exceeds 3 · 1011cm,3. The impurity turbulent transversal flow is directed inward and exceeds neoclassical flow significantly. The parallel conductivity and, as a consequence, turbulent transport are increased significantly by impurity radiation. The radiation loss dependence on the neutral Hydrogen concentration at the wall is also examined. The hydrogen concentration increasing the plasma density also rises. The relative beryllium concentration decreases. In total, these two effects are compensated, and the level of radiation losses is changed insignificantly (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Numerical simulation of reinforcement strengthening for high-arch dams to resist strong earthquakes

    Yuchuan Long
    Abstract This paper focuses on analyzing the nonlinear seismic response of high-arch dams with cantilever reinforcement strengthening. A modified embedded-steel model is presented to evaluate the effects of the strengthening measure on alleviating the extension and opening of cracks under strong earthquakes. By stiffening reinforced steel, this model can easily consider the steel,concrete interaction for lightly reinforced concrete (RC) members without the need of dividing them into RC and plain concrete zones. The new tensile constitutive relations of reinforced steel are derived from the load,deformation relationship of RC members in direct tension. This model has been implemented in the finite element code and its applicability is verified by two numerical simulations for RC tests. Subsequently, numerical analyses for a 210-m high-arch dam (Dagangshan arch dam) are conducted with and without the presence of cantilever reinforcement. Numerical results show that reinforcement strengthening can reduce the nonlinear response of the arch dam, e.g. joint opening and crest displacement, and limit the extension and opening width of concrete cracks. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Numerical simulation of reservoir sediment and effects on hydro-dynamic response of arch dams

    Chuhan Zhang
    Abstract Based on the dynamic theory for saturated porous media by Biot (Journal of the Acoustical Society of America 1956; 28: 168,178), a numerical model is presented to analyse the reflection behaviours of reservoir sediment and compared with those from the visco-elastic model. It is concluded that the two models give very similar results of reflection coefficient , within the frequency range of interest. Then, using the two models, the change of the reflection coefficients , with various sedimentation parameters and excitation frequencies are studied in detail. The results are further used in the analysis of response functions of hydro-dynamic pressures on, and structural displacements of the Xiang Hong Dian arch dam, for which some results from a field vibration test are available. It appears that effects of water compressibility with sediment reflection on hydro-dynamic pressures and structural response are not significant for this specific case. Copyright © 2001 John Wiley & Sons, Ltd. [source]

    Numerical simulation of sediment-associated water quality processes for a Mississippi delta lake

    ECOHYDROLOGY, Issue 3 2009
    Xiaobo Chao
    Abstract Three major sediment-associated processes were presented to describe the effects of sediment on the water quality processes, including the effect of sediment on the light intensity for the growth of phytoplankton (PHYTO), the adsorption,desorption of nutrients by sediment and the release of nutrients from the bed sediment layer. A formula was generated from field measurements to calculate the light attenuation coefficient by considering the effects of concentrations of chlorophyll and suspended sediment (SS). The concentrations of adsorbed and dissolved nutrients because of adsorption,desorption were calculated using two formulas that were derived based on the Langmuir Equation. The release rates of nutrients from the bed sediment were calculated by considering the effects of the concentration gradient across the water-sediment interface, pH, temperature and dissolved oxygen (DO) concentration. Model algorithms describing the adsorption and desorption of nutrients from sediment particles as well as the release of nutrients from bed sediment were tested using experimental data. These sediment-associated water quality processes were included in a three-dimensional (3D) water quality model, CCHE3D_WQ, developed by the National Center for Computational Hydroscience and Engineering (NCCHE), to simulate the concentrations of PHYTO and nutrients in a shallow Mississippi Delta lake with special emphasis on sediment-related processes. The simulated concentration of PHYTO (as chlorophyll) and nutrients were generally in good agreement with field observations. This study shows that there are strong interactions between sediment-associated processes and water quality constituents. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Numerical simulation on operation of closed-loop experimental facility with subsonic MHD generator

    Hidemasa Takana
    Abstract The operating characteristics and operation procedure of the closed-loop experimental facility under subsonic power generation have been investigated by means of time-dependent quasi-one-dimensional numerical simulations. Two ways of operation for subsonic power generation were found: (1) subsonic operation both under nonpower and power generation and (2) supersonic operation under nonpower generation and subsonic operation under power generation. For operation (1), Mach number at channel inlet decreases to ,0.6, therefore it is required to generate plasma under this Mach number. On the other hand, if the plasma cannot be generated, operation (2) needs to be carried out. In this case, a shock wave appears in the generator channel, then the influence of a large pressure change and a vibration caused by a shock wave in the generator channel needs to be considered. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(1): 25,33, 2008; Published online in Wiley InterScience ( DOI 10.1002/eej.20399 [source]

    Numerical simulation of thermal interaction between polymer and argon induction thermal plasma

    Yoshitaka Takeuchi
    Abstract Influence of polymer powder injection into Ar thermal plasmas was investigated by numerical approaches. Thermal plasma,polymer solid coupling phenomena such as melting and evaporation were considered to study plasma-quenching effect of polymer injection. Dominant process for decay of plasma temperature was examined by changing thermodynamic parameters such as melting, boiling temperatures and their latent heats of solid and liquid polymers. As a result, thermodynamic properties of evaporated polymer vapor directly affect plasma-quenching phenomena more markedly than the properties of liquid and solid which influence plasma quenching efficiency through the amount of evaporation. © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 92(1): 24,33, 2009; Published online in Wiley InterScience ( DOI 10.1002/ecj.10226 [source]

    Numerical simulation of DNA sample preconcentration in microdevice electrophoresis

    ELECTROPHORESIS, Issue 6 2005
    Alok Srivastava
    Abstract A numerical model is presented for the accurate and efficient prediction of preconcentration and transport of DNA during sample introduction and injection in microcapillary electrophoresis. The model incorporates conservation laws for the different buffer ions, salt ions, and DNA sample, coupled through a Gaussian electric field to account for the field modifications that cause electromigration. The accuracy and efficiency required to capture the physics associated with such a complex transient problem are realized by the use of the finite element-flux corrected transport (FE-FCT) algorithm in two dimensions. The model has been employed for the prediction of DNA sample preconcentration and transport during electrophoresis in a double-T injector microdevice. To test its validity, the numerical results have been compared with the corresponding experimental data under similar conditions, and excellent agreement has been found. Finally, detailed results from a simulation of DNA sample preconcentration in electrophoretic microdevices are presented using as parameters the electric field strength and the other species concentrations. The effect of the Tris concentration on sample stacking is also investigated. These results demonstrate the great potential offered by the model for future optimization of such microchip devices with respect to significantly enhanced speed and resolution of sample separation. [source]

    Numerical simulation of rotating bending process for U-tubes in heat exchangers

    H.-S. KIM
    ABSTRACT Heat exchangers comprise thousands of tubes having U-shaped portions. Rotating bending method has been widely utilized to make U-bends. Although this method shows an excellent performance, cracks have been frequently detected in the U-bends due to residual stresses induced by bending. In this paper, the bending process is simulated based on elastic,plastic finite element analyses in order to investigate the magnitude and distribution of the residual stresses including the effects of operating pressure. Analyses results show that the residual stress increases as the radius of U-bend decreases and that operating pressure has a detrimental effect in terms of stress corrosion cracking at the intrados of U-bend. It is thought that these results can be utilized for the estimations of fracture mechanics parameters such as limit load, stress intensity factor and J-integral, prevention of the cracking, and establishment of the optimum inspection strategy for the heat exchanger tubes. [source]

    Recharge and Preservation of Laurentide Glacial Melt Water in the Canadian Shield

    GROUND WATER, Issue 5 2000
    Ian D. Clark
    Ground water inflows to drifts ranging from 700 to 1615 m below ground surface at the Con Mine, Yellowknife, Northwest Territories, Canada, were used to study deep hydrogeological flow regimes in Shield terrain. Salinity trends are due to mixing between low-TDS ground water and deep Ca(Na)-C1 brines (>290 g/L) likely derived from Devonian sea water. C1 - ,,18O relationships demonstrate that all inflows are a mixture of three distinct components: modern meteoric ground water (,18O ,,18.9 ± 0.1%o), brine (,18O ,,10%o), and an isotopically depleted water (,18O ,,28%o). The origin of this third endmember is attributed to glacial melt water injected into the subsurface during ablation of the Laurentide Ice Sheet at ca. 10 ka. A mechanism is proposed where high hydrostatic pressure in the ablation zone imposes strong downward gradients beneath the ice sheet margin. Numerical simulation with the SWIFT II finite-difference code recreates the observed salinity gradients within a modeled 50-year interval, corresponding with the rate of retreat of the ice sheet across the landscape at this time. The persistence of this melt water in the subsurface for some 10,000 years following retreat of the ice and decay of the steep hydraulic gradients highlights the importance of gradient, in addition to permeability, as a major control on ground water flow and transport in deep crystalline settings. [source]

    Numerical simulation of heat transfer and fluid flow over two rotating circular cylinders at low Reynolds number

    Nikolay Pavlovich Moshkin
    Abstract This paper presents a numerical investigation of the characteristics of two-dimensional heat transfer in a steady laminar flow around two rotating circular cylinders in a side-by-side arrangement. The simulation is validated by comparing our computational results for the large gap-spacing between cylinder surfaces with the available numerical and experimental data for a single cylinder. Numerical simulations were carried out for the Reynolds number range 10,Re ,40, for the Prandtl number range 0.7,Pr ,50, and for a variety of absolute rotational speeds (|,|,2.5) at different gap spacings. The study revealed that for the range of parameters considered the rate of heat transfer decreases with the increasing speed of rotation. An increase of the Prandtl number resulted in an increase in the average Nusselt number. The streamlines and isotherms are plotted for a numbers of cases to show the details of the velocity and thermal fields. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience ( DOI 10.1002/htj.20293 [source]

    Numerical simulation of asymmetrical flow and heat transfer behind a hill in shear flows

    Hideki Yanaoka
    Abstract Three-dimensional numerical simulations of asymmetrical flows and heat transfer around a hill in shear flows were performed. When shear velocity distributions are introduced at the inlet, a vortex pair is formed asymmetrically to the spanwise direction behind the hill. Further, an asymmetrical hairpin vortex is periodically generated downstream. The leg of the asymmetrical hairpin vortex on the high-speed side collapses first. Further downstream, the asymmetrical hairpin vortex breaks down earlier than the symmetrical hairpin vortex, and streamwise vortices appear on the high-speed side. These streamwise vortices increase the heat transfer downstream. In contrast, no hairpin vortex appears in the case of a strong shear velocity distribution, but instead a streamwise vortex appears. The heat transfer decreases downstream since the turbulence generated by streamwise vortices is weak. © 2008 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience ( DOI 10.1002/htj.20223 [source]

    Numerical simulation of non-isothermal phase change problem using ADRBEM with augmented items

    Jie Liu
    Abstract In this paper, the phase change moving interface problem along the axial direction of the cylinder in the lead alloys containing tin is simulated by the axisymmetric dual reciprocity boundary element method (ADRBEM) with augmented items. The numerical method is verified by comparing with the analytical solution under a certain condition. The calculating results show that the ADRBEM with augmented items is an effective numerical method to solve the analogous problem of non-isothermal phase change, which occurs in the crystal growth process. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(7): 408, 416, 2007; Published online in Wiley InterScience ( DOI 10.1002/htj.20173 [source]

    Numerical simulation of drop deformation and breakup in shear flow

    Lin Chang-Zhi
    Abstract Three-dimensional numerical simulation of the deformation and breakup of an isolated liquid drop suspended in immiscible viscous fluid under shear flow was performed with diffuse interface method. The governing equations of the model were described by Navier, Stokes, Cahn, Hilliard equations. The surface tension was treated as a modified stress. In this paper, a uniform staggered Cartesian grid was used. The transient Navier, Stokes equations were solved by an approximation projection method based on pressure increment formulation, while the Cahn, Hilliard equations were solved by a nonlinear full approximation multigrid method. The numerical results of the drop deformation and breakup were in good agreement with the experimental measurements. Therefore, the present model could be perfectly applied to study the mechanism of drop deformation and breakup. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(5): 286, 294, 2007; Published online in Wiley InterScience ( DOI 10.1002/htj.20160 [source]

    Numerical simulation of model scramjet combustor flowfield

    Yuan-Guang Wang
    Abstract A new concept has been raised and adopted in this paper to enlarge the scope of the two-dimensional model particularly for the purpose of dealing with three-dimensional normal injection cases. Meanwhile, the method has a very good performance for its short cyclic period. The new idea was realized through special resolution with continuity equations; i.e., mass flow was directly added in the source term of the continuity equation. To prove the robustness of this illuminating method, comparisons using calculations were carried out, and the results are satisfactory. A model scramjet combustor tested on the free-jet scramjet test facility was illustrated and underwent numerical calculations with the two-dimensional program, adopting the above simplified injecting method. To simulate the chemical reaction process in the scramjet tunnel, a five-species, single-step reaction model was introduced in the calculation process. This research presents the major aerodynamic parameters and components of mass fraction distribution within the model combustor channel, which made it easy to observe and analyze the flowfield. Finally, wall pressure comparisons between the numerical and experimental results were carried out to verify the accuracy of the calculation model. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(5): 295, 302, 2007; Published online in Wiley InterScience ( DOI 10.1002/htj.20159 [source]

    Numerical simulation of rime ice accretion process on an airfoil

    Zhang Da-lin
    Abstract To simulate the ice accretion on an airfoil, a boundary moving technique is proposed to deal with the distortion of the airfoil surface due to ice accretion on the leading edge. Incorporating the two-phase model of air-supercooled droplets in the Eulerian coordinate system, this technique is applied to simulate the process of the rime ice accretion (the droplets freeze at the instant impinging on the airfoil) on the NACA 0012 airfoil, and the ice profile after ice accretion is achieved successfully. A brief comparison between the results of this paper and the experiment data indicates that the current method is applicable and effective. © 2005 Wiley Periodicals, Inc. Heat Trans Asian Res, 34(4): 226,234, 2005; Published online in Wiley InterScience ( DOI 10.1002/htj.20064 [source]