Numerical Validation (numerical + validation)

Distribution by Scientific Domains


Selected Abstracts


Numerical prediction of the hydrodynamic performance of a centrifugal pump in cavitating flows

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 5 2007
Jun Li
Abstract A computational modelling for the prediction of the hydrodynamic performance of a centrifugal pump in cavitating flows is presented in this paper. The cavitation model is implemented in a viscous Reynolds-averaged Navier,Stokes solver. The cavity interface and shape are determined using an iterative procedure matching the cavity surface to a constant pressure boundary. The pressure distribution, as well as its gradient on the wall, is taken into account in updating the cavity shape iteratively. Numerical validation of the present cavitation model and algorithms is performed on different headform/cylinder bodies for a range of cavitation numbers through comparing with the experimental data. Flow characteristics trends associated with off-design flow and twin cavities in the blade channel are observed using the presented cavitation prediction. The rapid drop in head coefficient at low cavitation number is captured for two different flow coefficients. Local flow field solution illustrates the principle physical mechanisms associated with the onset of breakdown. Copyright © 2006 John Wiley & Sons, Ltd. [source]


Harmonic balance method for FEM analysis of fluid flow in a vibrating pipe

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 5 2006
M. Ragulskis
Abstract A numerical procedure for the analysis of non-Newtonian fluid flow in a longitudinally vibrating tube is developed. The formulation of the problem is presented in differential equation form and finite element model is developed leading to the first-order matrix differential equation. A special modification of the harmonic balance procedure is proposed for this non-linear problem. Numerical validation of the harmonic balance procedure was performed by comparison of the average mass flow rate with the results of direct time integration. Copyright © 2005 John Wiley & Sons, Ltd. [source]


Theory and finite element computation of cyclic martensitic phase transformation at finite strain

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 1 2008
Erwin Stein
Abstract A generalized variational formulation, including quasi-convexification of energy wells for arbitrarily many martensitic variants in case of mono-crystals for linearized strains, was developed by Govindjee and Miehe (Comp. Meth. Appl. Mech. Eng. 2001; 191(3,5):215,238) and computationally extended by Stein and Zwickert (Comput. Mech. 2006; in press). This work is generalized here for finite strain kinematics with monotonous hyperelastic stress,strain functions in order to account for large transformation strains that can reach up to 15%. A major theoretical and numerical difficulty herein is the convexification of the finite deformation phase transformation (PT) problems for multiple phase variants, n,2. A lower bound of the mixing energy is provided by the Reuss bound in case of linear kinematics and an arbitrary number of variants, shown by Govindjee et al. (J. Mech. Phys. Solids 2003; 51(4):I,XXVI). In case of finite strains, a generalized representation of free energy of mixing is introduced for a quasi-Reuss bound, which in general holds for n,2. Numerical validation of the used micro,macro material model is presented by comparing verified numerical results with the experimental data for Cu82Al14Ni4 monocrystals for quasiplastic PT, provided by Xiangyang et al. (J. Mech. Phys. Solids 2000; 48:2163,2182). The zigzag-type experimental stress,strain curve within PT at loading, called ,yield tooth', is approximated within the finite element analysis by a smoothly decreasing and then increasing axial stress which could not be achieved with linearized kinematics yielding a constant axial stress during PT. Copyright © 2007 John Wiley & Sons, Ltd. [source]


Dielectric resonator antenna: Operation of the magnetodielectric composites Cr0.75Fe1.25O3 (CRFO)/Fe0.5Cu0.75Ti0.75O3 (FCTO)

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2007
H. H. B. Rocha
Abstract The probe-feed cylindrical dielectric resonator antennas (DRA) based on a new magnetodielectric composites Cr0.75Fe1.25O3 (CRFO)/Fe0.5Cu0.75Ti0.75O3 (FCTO) are investigated. The experimental and theoretical characteristics of the antenna like return loss, bandwidth, input impedance, and radiation patterns are in good agreement. Numerical validation is done, tacking into account the air gaps between the dielectric resonator and the metallic conductors. Frequency response bandwidth in the range of 6.6,11.8% was obtained for frequency operation around 4 GHz. The CRFO-FCTO present a dielectric constant in the range of 8,13 with loss around 10,3. To summarize, the performance of a cylindrical DRA based in a new matrix CRFO/FCTO was examined. These measurements confirm the potential use of such materials for small DRA. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 409,413, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22160 [source]


Generalized probabilistic approach of uncertainties in computational dynamics using random matrices and polynomial chaos decompositions

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 8 2010
Christian Soize
Abstract A new generalized probabilistic approach of uncertainties is proposed for computational model in structural linear dynamics and can be extended without difficulty to computational linear vibroacoustics and to computational non-linear structural dynamics. This method allows the prior probability model of each type of uncertainties (model-parameter uncertainties and modeling errors) to be separately constructed and identified. The modeling errors are not taken into account with the usual output-prediction-error method, but with the nonparametric probabilistic approach of modeling errors recently introduced and based on the use of the random matrix theory. The theory, an identification procedure and a numerical validation are presented. Then a chaos decomposition with random coefficients is proposed to represent the prior probabilistic model of random responses. The random germ is related to the prior probability model of model-parameter uncertainties. The random coefficients are related to the prior probability model of modeling errors and then depends on the random matrices introduced by the nonparametric probabilistic approach of modeling errors. A validation is presented. Finally, a future perspective is introduced when experimental data are available. The prior probability model of the random coefficients can be improved in constructing a posterior probability model using the Bayesian approach. Copyright © 2009 John Wiley & Sons, Ltd. [source]


Analysis of Twin Data Using SAS

BIOMETRICS, Issue 2 2009
Rui Feng
Summary Twin studies are essential for assessing disease inheritance. Data generated from twin studies are traditionally analyzed using specialized computational programs. For many researchers, especially those who are new to twin studies, understanding and using those specialized computational programs can be a daunting task. Given that SAS (Statistical Analysis Software) is the most popular software for statistical analysis, we suggest that the use of SAS procedures for twin data may be a helpful alternative and demonstrate that we can obtain similar results from SAS to those produced by specialized computational programs. This numerical validation is practically useful, because a natural concern with general statistical software is whether it can deal with data that are generated from special study designs such as twin studies and if it can test a particular hypothesis. We concluded through our extensive simulation that SAS procedures can be used easily as a very convenient alternative to specialized programs for twin data analysis. [source]