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  • Open Access

    ARTICLE

    Variable Viscosity and Density Biofilm Simulations using an Immersed Boundary Method, Part I: Numerical Scheme and Convergence Results

    Jason F. Hammond1, Elizabeth J. Stewart2, John G. Younger3, Michael J.Solomon2, David M. Bortz4,5

    CMES-Computer Modeling in Engineering & Sciences, Vol.98, No.3, pp. 295-340, 2014, DOI:10.32604/cmes.2014.098.295

    Abstract The overall goal of this work is to develop a numerical simulation which correctly describes a bacterial biofilm fluid-structure interaction and separation process. In this, the first of a two-part effort, we fully develop a convergent scheme and provide numerical evidence for the method order as well as a full 3D separation simulation. We use an immersed boundary-based method (IBM) to model and simulate a biofilm with density and viscosity values different from than that of the surrounding fluid. The simulation also includes breakable springs connecting the bacteria in the biofilm which allows the inclusion… More >

  • Open Access

    ARTICLE

    NUMERICAL INVESTIGATIONS ON COMBUSTION AND EMISSION CHARACTERISTICS IN A DIRECT INJECTION DIESEL ENGINE AT ELEVATED FUEL TEMPERATURES

    Manimaran Renganathan, Thundil Karuppa Raj Rajagopal*

    Frontiers in Heat and Mass Transfer, Vol.4, No.1, pp. 1-11, 2013, DOI:10.5098/hmt.v4.1.3008

    Abstract In this work, fuel spray parameters are studied by varying the fuel temperature. To overcome the tedious experimental task, a 3-D Computational Fluid Dynamics methodology is adopted by injecting fuel at specified temperatures of 313 K, 353 K and 393 K. The validation is accomplished after the optimal spatial and temporal steps of discretization are found out. At a fuel temperature of 313 K, advancing the injection timing from 6 deg bTDC to 20 deg bTDC increases cylinder peak pressure from 79.8 bar to 90.9 bar. Relation between the emission characteristics and spray SMD and More >

  • Open Access

    ARTICLE

    ANALYSIS OF CHAOTIC NATURAL CONVECTION IN A TALL RECTANGULAR CAVITY WITH NON-ISOTHERMAL WALLS

    Heather Dillona , Ashley Emeryb,† , Ann Mescherb

    Frontiers in Heat and Mass Transfer, Vol.4, No.2, pp. 1-9, 2013, DOI:10.5098/hmt.v4.2.3004

    Abstract A computational model is presented that extends prior work on unsteady natural convection in a tall rectangular cavity with aspect ratio 10 and applies Proper Orthogonal Decomposition to the results. The solution to the weakly compressible Navier-Stokes equation is computed for a range of Rayleigh numbers between 2 × 107 and 2.2 × 108 with Prandtl number 0.71. A detailed spectral analysis shows dynamic system behavior beyond the Hopf bifurcation that was not previously observed. The wider Rayleigh range reveals new dynamic system behavior for the rectangular geometry, specifically a return to a stable oscillatory behavior More >

  • Open Access

    ARTICLE

    SIMULATION OF EMBOLIZATION PARTICLE TRAJECTORIES

    Nessa Johnson, John Abraham*, Zach Helgeson, Michael Hennessey

    Frontiers in Heat and Mass Transfer, Vol.2, No.2, pp. 1-7, 2011, DOI:10.5098/hmt.v2.2.3006

    Abstract A numerical simulation has been performed on the hemodynamics associated with embolization procedures. The flow geometry includes a multibranch artery which is upstream of a targeted tumor. During the procedure, drug-eluting particles are released into the local arterial geometry and are carried downstream by the flowing blood. The intention is to cause embolization of a daughter artery which feeds the tumor. As particles are injected into the blood stream, and as the embolization progresses, it is possible for the particulates to substantially alter the blood flow in the main artery. This alteration may lead to… More >

  • Open Access

    ARTICLE

    The Importance of Adequate Turbulence Modeling in Fluid Flows

    L.Q. Moreira1, F.P. Mariano2, A. Silveira-Neto1

    CMES-Computer Modeling in Engineering & Sciences, Vol.75, No.2, pp. 113-140, 2011, DOI:10.3970/cmes.2011.075.113

    Abstract Turbulence in fluid flow is one of the most challenging problems in classical physics. It is a very important research problem because of its numerous implications, such as industrial applications that involve processes using mixtures of components, heat transfer and lubrication and injection of fuel into the combustion chambers and propulsion systems of airplanes. Turbulence in flow presents characteristics that are fully nonlinear and that occur at high Reynolds numbers. Because of the nonlinear nature of turbulent flow, an increase in the Reynolds number implies an increase in the Kolmogorov wave numbers, and the flow… More >

  • Open Access

    ARTICLE

    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… More >

  • Open Access

    ARTICLE

    Accurate True Direction Solutions to the Euler Equations Using a Uniform Distribution Equilibrium Method

    Alex Ferguson1, Matthew R. Smith2, J.-S. Wu3

    CMES-Computer Modeling in Engineering & Sciences, Vol.63, No.1, pp. 79-100, 2010, DOI:10.3970/cmes.2010.063.079

    Abstract A novel approach for the use of multiple continuous uniform distributions for reconstruction of the Maxwell-Boltzmann equilibrium probability distribution function is used for the solution of one and two dimensional Euler equations. The Uniform distribution Equilibrium Flux Method (UEFM) is a kinetic-theory based flux solver which calculates true directional, volume to volume fluxes based on integration (over velocity space and physical space) of a sum of uniform probability distribution functions working to approximate the equilibrium distribution function. The resulting flux expressions contain only the Heaviside unit step function and do not require the evaluation of More >

  • Open Access

    ARTICLE

    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 More >

  • Open Access

    ARTICLE

    Numerical Simulations of Flows over a Pair of Cylinders at Different Arrangements using the Immersed Boundary Method

    A.R. da Silva1, A. Silveira-Neto2,3, D.A. Rade2,4, R.Francis4, E.A. Santos4

    CMES-Computer Modeling in Engineering & Sciences, Vol.50, No.3, pp. 285-304, 2009, DOI:10.3970/cmes.2009.050.285

    Abstract In the context of computational fluid dynamics a numerical investigation of incompressible flow around fixed pairs of rigid circular cylinders was carried out. The two-dimensional filtered Navier-Stokes equations with the Smagorinsky sub-grid scale model were solved using a Cartesian non-uniform grid. The immersed Boundary Method with the Virtual Physical Model was used in order to model the presence of two circular cylinders embedded in the flow. The fractional time step method was used to couple pressure and velocity fields. The simulations were carried out for Reynolds number equal to 72,000 for pitch ratio equal to More >

  • Open Access

    ARTICLE

    A Computational Fluid Dynamics Study of a 2D Airfoil in Hovering Flight Under Ground Effect

    J.M.C.Pereira1, N.A.R.Maia1, J.C.F.Pereira1

    CMES-Computer Modeling in Engineering & Sciences, Vol.49, No.2, pp. 113-142, 2009, DOI:10.3970/cmes.2009.049.113

    Abstract We present a 2D incompressible Navier-Stokes numerical simulation of a virtual model of an elliptic, or flat plate, foil in hovering flight configuration. Computations obtained with a general purpose solver were validated against reference data on forward flapping flight, normal or dragonfly hovering. The moving mesh technique allows airfoil translation and angular mesh movement accompaining the airfoil stroke motion. Close to the ground the mesh deforms to occupy the narrow computational domain formed between the airfoil and the ground. Computations have been carried out for some parameters, including the distances h between the foil center and… More >

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