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SUMMARY In this study, an improved and robust one-dimensional human arterial network model is presented. The one-dimensional blood flow equations are solved using the Taylor-locally conservative Galerkin finite element method. The model improvements are carried out by adopting parts of the physical models from different authors to establish an accurate baseline model. The predicted pressure-flow waveforms at various monitoring positions are compared against in vivo measurements from published works. The results obtained show that wave shapes predicted are similar to that of the experimental data and exhibit a good overall agreement with measured waveforms. Finally, computational studies on the influence of an abdominal aortic aneurysm are presented. The presence of aneurysms results in a significant change in the waveforms throughout the network. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

An electroosmotic flow (EOF)-based heat spreader is studied using the finite-element method and an artificial compressibility-based time-stepping scheme. The heat spreader consists of a microprocessor, microchannels, and a standard plate-fin heat sink. All three components are assumed to be tightly integrated. The microchannels are used to induce EOF, and a conjugate heat transfer analysis is carried out in the presence of the EOF. The heat transfer results from the microprocessor surface to the EOF channel and from the EOF channel to the plate-fin heat sink show clearly that the EOF enhances heat transfer and thus it has the potential to be used as an effective heat spreader mechanism. For the materials and parameters used, the temperature at a section above the microchannel has been reduced by up to 6°C. This is equivalent to reducing the heat-sink fin height by a length equal to about the depth of the microchannel employed. [ABSTRACT FROM AUTHOR]

In this paper, numerical investigation of airflow through a human upper airway is presented using an unstructured-based characteristic-based split (CBS) scheme. The CBS scheme used in the present study employs a fully explicit matrix-free solution procedure along with artificial compressibility. A one equation Spalrat–Allmaras (SA) turbulence model is employed to study low and moderate Reynolds number flows. A detailed discussion of the qualitative and quantitative results is presented. The results show a strong influence of the Reynolds number on the flow pattern and quantities of interest, pressure drop and wall shear stress. It is also apparent that SA model can be employed on unstructured meshes to predict the steady flow with good accuracy. Thus, the novelties of the present paper are: use of the unstructured mesh-based solution algorithm and the successful application of the SA model to a typical human upper airway. Copyright © 2006 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A matrix free fractional step method for solid mechanics problems is presented. The proposed method permits solution of incompressible solid mechanics equations and if necessary compressibility can be introduced. The local time stepping employed makes the proposed approach more robust than standard explicit methods. The transient solution is established via a dual time stepping approach. In the dual time stepping method, the inner time step (pseudo time step) is restricted by the explicit time step limit but the real time step has no limits on its value. Some linear static and dynamic problems are solved to demonstrate the proposed matrix free method. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we present the analysis of an explicit and matrix free fractional step method for incompressible flows. The presented method can be employed in either conservation or non-conservation form. The stabilization, convergence and conservation aspects of the presented method are discussed. A procedure for eliminating the first order error in time introduced by the split is proposed. Some benchmark steady and unsteady state examples are presented to demonstrate the proposed new aspects of the matrix free scheme. [Copyright &y& Elsevier]

Abstract: An artificial compressibility method is presented for the solution of incompressible turbulent flow problems at moderate Reynolds numbers. The presented approach has been used to solve both steady and unsteady state turbulent flow problems. Three different RANS models have been employed to investigate the application of present matrix solution free approach. They are one-equation model of Wolfstein, Spalart–Allmaras model and standard κ–ε model. In addition to the results of standard steady two-dimensional flow problems, solutions to transient two-dimensional flow past a circular cylinder and steady state three-dimensional turbulent flow in a model “upper human airway” are also presented. The results presented demonstrate that the artificial compressibility based CBS scheme is suitable for both steady and unsteady state incompressible turbulent flow calculations at moderate Reynolds numbers. [Copyright &y& Elsevier]

In this article a locally conservative Galerkin finite-element approach is proposed for transient conservation equations using linear triangular elements. The method proposed follows a simple postprocessing procedure at each time step and evaluates a numerical flux on the element edges. The proposed method requires inversion of only a 3  ×  3 matrix, per element, in its implicit form. The system of simultaneous equations is solved over individual elements independently of the surrounding element equation sets. The situation of multiple solutions at a node is eliminated by taking the average among the solutions obtained from the surrounding elements. Both diffusion and convection-diffusion problems are solved in one and two dimensions and compared with analytical solutions. [ABSTRACT FROM AUTHOR]

The differences in existing porous medium flow models and their effect on flow and heat transfer are discussed. A fluid-saturated porous medium subjected to constant heat flux has been considered. The Galerkin finite element method coupled with the velocity correction procedure is used to solve a set of generalized porous medium equations. Results are presented for a wide range of Darcy and Rayleigh numbers. Copyright © 1999 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The complexities in the flow pattern in a cavo-pulmonary vascular system—after application of the Fontan procedure in the vicinity of the superior vena cava, inferior vena cava, and the confluence at the T-junction—are analysed. A characteristic-based split (CBS) finite element scheme involving the artificial compressibility approach is employed to compute the resulting flow. Benchmarking of the CBS scheme is carried out using standard problems and with the flow features observed in an experimental model with the help of a dye visualization technique in model scale. The transient flow variations in a total cavo-pulmonary connection (TCPC) under pulsatile conditions are investigated and compared with flow visualization studies. In addition to such qualitative flow investigations, quantitative analysis of energy loss and haemodynamic stresses have also been performed. The comparisons show good agreement between the numerical and experimental flow patterns. The numerically predicted shear stress values indicate that the pulsatile flow condition is likely to be more severe than steady flow, with regard to the long-term health of the surgically corrected TCPC. Copyright © 2008 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]