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  • Open Access


    A Spectrally Accurate Quadrature for 3-D Boundary Integrals

    Gregory Baker1, Huaijian Zhang1

    CMES-Computer Modeling in Engineering & Sciences, Vol.80, No.3&4, pp. 219-232, 2011, DOI:10.3970/cmes.2011.080.219

    Abstract Boundary integral methods have proved very useful in the simulation of free surface motion, in part, because only information at the surface is necessary to track its motion. However, the velocity of the surface must be calculated quite accurately, and the error must be reasonably smooth, otherwise the surface buckles as numerical inaccuracies grow, leading to a failure in the simulation. For two-dimensional motion, the surface is just a curve and the boundary integrals are simple poles that may be removed, allowing spectrally accurate numerical integration. For three-dimensional motion, the singularity in the integrand, although weak, presents a greater challenge… More >

  • Open Access


    Study on 3D Unsteady Swirling Recirculating Flow in a Nozzle with a Slotted-tube

    Hui-Fen Guo1,2, Bin-Gang Xu1,3, Sheng-Yan Li1, Chong-Wen Yu2

    CMES-Computer Modeling in Engineering & Sciences, Vol.80, No.2, pp. 87-112, 2011, DOI:10.3970/cmes.2011.080.087

    Abstract Three-dimensional transient simulation is presented for swirling recirculating flow in a nozzle with a slotted-tube (different grooves) and the effect of the groove number is also investigated. The numerical results on the streamline angles are validated by experimental visualization using the surface oil flow technology. In the downstream center of the injectors, the vortex breakdown experiences a transition from bubble- to spiral- breakdown as time is increased. For all cases under study, as the sizes of two recirculation zones near the injector upstream wall and the step retain almost constant, the spiral breakdown shows a periodic development. The more the… More >

  • Open Access


    Uncertainty Quantification of the Interaction of a Vortex Pair With the Ground

    J.L. Sereno1, J.C.F. Pereira1

    CMES-Computer Modeling in Engineering & Sciences, Vol.73, No.1, pp. 23-44, 2011, DOI:10.3970/cmes.2011.073.023

    Abstract The evolution of a two-dimensional vortex pair in ground effect was studied under the influence of random initial inputs comprising vortex strength (circulation) or initial vortex position. The paper addresses the questions of how do variations and uncertainties of initial conditions translate to the variability of vortex pair evolution. The stochastic solutions were obtained recurring to the Polynomial Chaos Expansion method of random processes applied to the Navier-Stokes equations for a laminar flow. The method quantifies the extent, dependence and propagation of uncertainty through the model system and, in particular, a methodology for the calculation of the vortices trajectory variability,… More >

  • Open Access


    Calculation of a Deformable Membrane Airfoil in Hovering Flight

    D.M.S. Albuquerque1, J.M.C. Pereira1, J.C.F. Pereira1,2

    CMES-Computer Modeling in Engineering & Sciences, Vol.72, No.4, pp. 337-366, 2011, DOI:10.3970/cmes.2011.072.337

    Abstract A numerical study of fluid-structure interaction is presented for the analysis of viscous flow over a resonant membrane airfoil in hovering flight. A flexible membrane moving with a prescribed stroke period was naturally excited to enter into 1st, 2nd and 3rd mode of vibration according to the selected membrane tension. The Navier-Stokes equations were discretized on a moving body unstructured grid using the finite volume method. The instantaneous membrane position was predicted by the 1D unsteady membrane equation with input from the acting fluid flow forces. Following initial validation against reported rigid airfoils predictions, the model is applied to the… More >

  • Open Access


    A novel MLPG-Finite-Volume Mixed Method for Analyzing Stokesian Flows & Study of a new Vortex Mixing Flow

    Ruben Avila1, Zhidong Han2, Satya N. Atluri3

    CMES-Computer Modeling in Engineering & Sciences, Vol.71, No.4, pp. 363-396, 2011, DOI:10.3970/cmes.2011.071.363

    Abstract The two dimensional steady state Stokes equations are solved by using a novel MLPG-Mixed Finite Volume method, that is based on the independent meshless interpolations of the deviatoric velocity strain tensor, the volumetric velocity strain tensor, the velocity vector and the pressure. The pressure field directly obtained from this method does not suffer from the malady of checker-board patterns. Numerical simulations of the flow field, and trajectories of passive fluid elements in a new complex Stokes flow are also presented. The new flow geometry consists of three coaxial cylinders two of smaller diameter, that steadily rotate independently, inside a third… More >

  • Open Access


    Efficient Engineering Prediction of Turbulent Wing Tip Vortex Flows

    Sung-Eun Kim1, Shin Hyung Rhee2

    CMES-Computer Modeling in Engineering & Sciences, Vol.62, No.3, pp. 291-310, 2010, DOI:10.3970/cmes.2010.062.291

    Abstract Turbulent flow past a finite wing has been computed to assess the fidelity of modern computational fluid dynamics in predicting tip vortex flows. The efficacy of a feature-adaptive local mesh refinement to resolve the steep gradients in the flow field near the tip vortex is demonstrated. The impact of turbulence modeling is evaluated using several popular eddy viscosity models and a Reynolds stress transport model. The results indicate that the combination of a computational mesh with an adequate resolution, high-order spatial discretization scheme along with the use of advanced turbulence models can predict tip vortex flows with acceptable accuracy. More >

  • Open Access


    Vortex Ring Formation within a Spherical Container with Natural Convection

    Gerardo Anguiano-Orozco1,2, Rubén Avila3

    CMES-Computer Modeling in Engineering & Sciences, Vol.49, No.3, pp. 217-254, 2009, DOI:10.3970/cmes.2009.049.217

    Abstract A numerical investigation of the transient, three dimensional, laminar natural convection of a fluid confined in a spherical container is carried out. Initially the fluid is quiescent with a uniform temperature Ti equal to the temperature of the wall of the container. At time t=0, the temperature of the wall is suddenly lowered to a uniform temperature Tw=0. The natural convection, that conducts to a vortex ring formation within the sphere, is driven by a terrestrial gravity force (laboratory gravity) and by the step change in the temperature of the wall. A scaling analysis of a simplified transient, two dimensional… More >

  • Open Access


    Effect of Geometrical Parameters on Vortex Fluidic Oscillators Operating with Gases and Liquids

    T. Chekifi1,2,*, B. Dennai2, R. Khelfaoui2

    FDMP-Fluid Dynamics & Materials Processing, Vol.14, No.3, pp. 201-212, 2018, DOI: 10.3970/fdmp.2018.00322

    Abstract The fluidic oscillator is an interesting device developed for passive flow measurement. These microsystems can produce a high oscillating jet frequency with high flow velocity. The main advantages of fluidic oscillators are that no moving parts is included in the device. Commercial CFD code FLUENT was used to perform analysis of flows in fluidic oscillator. Numerical simulations were carried out for different flow conditions, where water and air were used as working fluids. The oscillation frequencies were identified by the discrete fast Fourier transform method (FFT). Furthermore a low-pressure vortex of fluid flow in the oscillating chamber was observed. The… More >

  • Open Access


    On the Vortex Formation Effect During the Application of a Nitrogen-Gas Assisted Laser-Fusion Cutting Technique to Stainless Steel

    S. Aggoune1, C. Abid2, E.H. Amara1,3

    FDMP-Fluid Dynamics & Materials Processing, Vol.11, No.2, pp. 115-125, 2015, DOI:10.3970/fdmp.2015.011.115

    Abstract This paper focuses on the vortex formation effect during the application of a laser-fusion cutting technique. This industrial technique is typically associated with the ejection of a film of molten stainless steel blown off by a subsonic laminar jet of nitrogen gas used to assist the process. Without taking into account the transverse movement of the workpiece, we consider a 4 mm thick stainless steel plate. The resulting molten metal flow is assumed to be laminar, steady, viscous and incompressible. The numerical results reveal vortex structures adjacent to the walls at the entrance of the kerf, and a pair of… More >

  • Open Access


    Grid-Free Vortex Method for Particle-Laden Gas Flow

    T. Uchiyama1

    FDMP-Fluid Dynamics & Materials Processing, Vol.7, No.4, pp. 371-388, 2011, DOI:10.3970/fdmp.2011.007.371

    Abstract This study proposes a three-dimensional grid-free method to simulate particle-laden gas flows. It is based on a vortex method. The flow region is not resolved into computational grids, but the gas vorticity field is discretized by vortex elements. The behavior of the vortex element and the particle motion are simultaneously calculated by using the Lagrangian approach. Eight cubic cells are locally allocated around each particle to compute the effect of the particle motion on the gas flow. In each cell, the change in the vorticity due to the particle is calculated, and it is considered by generating a vortex element… More >

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