Carmona, A.; Lehmkuhl, O.; Perez, C.; Oliva, A. Numerical heat transfer. Part B, fundamentals Vol. 67, num. 5, p. 410-436 DOI: 10.1080/10407790.2014.964575 Data de publicació: 2015-05-01 Article en revista
The aim of this work is to delve into the numerical analysis of viscoplastic-type non-Newtonian fluid flows. Specifically, improvements in the spatial discretization schemes and the temporal integration methods have been proposed to overcome the numerical problems introduced by the transpose diffusive term and associated with the velocity field discontinuity, the artificial viscous diffusion, and the transpose viscous coupling. The resulting knowledge may be useful, among many other reasons, to improve the corresponding numerical simulations and gain insight into the underlying physics of this class of non-Newtonian fluid flows.
Paniagua, L.; Lehmkuhl, O.; Oliet, C.; Perez, C. Numerical heat transfer. Part B, fundamentals Vol. 65, num. 2, p. 103-128 DOI: 10.1080/10407790.2013.846712 Data de publicació: 2014-02-01 Article en revista
In this article, the three-dimensional turbulent forced convection in a matrix of wall-bounded 8 × 8 cylindrical pins is studied. Large eddy simulations (LES) are performed for Reynolds numbers 3,000, 10,000 and 30,000. Three different subgrid-scale (SGS) models (WALE, QR, and VMS) are compared on a row-by-row study. Local values of velocity and pressure coefficient are depicted. Turbulence characteristics of the flow are well illustrated. The thermal field is analyzed and validated with the time-averaged Nusselt number at the end walls of the pin matrix. The capabilities of the methodology for predicting the turbulent flow features is also shown.
Galione, P.A.; Lehmkuhl, O.; Rigola, J.; Oliva, A. Numerical heat transfer. Part B, fundamentals Vol. 65, num. 1, p. 27-52 DOI: 10.1080/10407790.2013.836399 Data de publicació: 2013-11-09 Article en revista
Fixed-grid enthalpy models have been used extensively for solid-liquid phase-change computational fluid dynamics (CFD) simulations with implicit time schemes. In this work, this technique is implemented for explicit time schemes and collocated unstructured domain discretization, due to the interest in coupling phase-change formulations with turbulence models for liquid motion.
Issues regarding the form of the energy equation, the treatment of the pressure equation, as well as the momentum source term coefficient introduced by the enthalpy–porosity method are described in detail.
Numerical implementation is tested with different study cases, showing good agreement with other experimental and numerical results.
Jofre, L.; Lehmkuhl, O.; Ventosa-Molina, J.; Trias, F. X.; Oliva, A. Numerical heat transfer. Part B, fundamentals Vol. 65, num. 1, p. 53-79 DOI: 10.1080/10407790.2013.836335 Data de publicació: 2013-11-09 Article en revista
The Navier-Stokes equations describe fluid flow by conserving mass and momentum. There are two main mesh discretizations for the computation of these equations, the collocated and staggered schemes. Collocated schemes locate the velocity field at the same grid points as the pressure one, while staggered discretizations locate variables at different points within the mesh. One of the most important characteristic of the discretization schemes, aside from accuracy, is their capacity to discretely conserve kinetic energy, specially when solving turbulent flow. Hence, this work analyzes the accuracy and conservation properties of two particular collocated and staggered schemes by solving various problems.
An efficient self-adaptive strategy for the explicit time integration of Navier-Stokes equations is presented. Unlike the conventional explicit integration schemes, it is not based on a standard CFL condition. Instead, the eigenvalues of the dynamical system are analytically bounded and the linear stability domain of the time-integration scheme is adapted in order
to maximize the time step. The method works independently of the underlying spatial mesh;
therefore, it can be easily integrated into structured or unstructured codes. The additional computational cost is minimal, and a significant increase of the time step is achieved without losing accuracy. The effectiveness and robustness of the method are demonstrated on both a Cartesian staggered and an unstructured collocated formulation. In practice, CPU cost reductions up to more than 4 with respect to the conventional approach have been measured.
Cadafalch, J.; Oliva, A.; Perez, C.; Costa, M.; Salom, J. Numerical heat transfer. Part B, fundamentals Vol. 35, num. 1, p. 65-84 DOI: 10.1080/104077999276018 Data de publicació: 1999-01 Article en revista
This study examines the resolution of the Navier-Stokes equations for laminar natural or forced incompressible flows by means of the domain decomposition method. Conservative and nonconservative interpolation schemes available in the literature are studied and compared to a formulation based completely on finite-volume techniques. The discretized governing equations are obtained in each subdomain using a finite-volume method on staggered grids and are solved adopting a pressure-based segregated algorithm. A mesh refinement study and the generalized Richardson extrapolation have been adopted to evaluate the errors and the order of accuracy of each interpolation scheme. Illustrative numerical results of a complex flow through a junction are shown.