Consistent calculation of heat fluxes through solid boundaries applied to natural convection problems

Calculations of heat fluxes through cooled/heated walls from CFD results have become of great importance in many industrial applications. The objective of this work is to present a consistent numerical technique to compute heat fluxes through isothermal boundaries. In the present paper, we consider a stabilized PSPG/SUPG finite element scheme for the steady Navier-Stokes equations for variable density flows. Three variants are considered which differ by the treatment of the convective terms in the momentum and energy equations, i.e. a convective formulation, a corrected convective formulation and a conservative formulation. A pseudo Newton method is employed as non linear solver. A numerical technique to compute the boundary heat fluxes consistent with the finite element formulation is then presented, as well as the expression obtained using the gradient of the finite element approximation Th To illustrate the effect of the formulation, numerical simulations of natural convection of air in 2D and 3D cubic cavities with large temperature differences between opposite walls are carried out. The effects of the finite element formulation, of the expression for the calculation of the heat flux and of mesh refinement are presented. The results demonstrate the superior accuracy and convergence of the proposed numerical technique for the heat flux computation. © Published under licence by IOP Publishing Ltd.SCOPUS: cp.jinfo:eu-repo/semantics/publishe

[Celiac-disease in Adult - Clinical-features and Role of Endoscopy]

Adult coeliac disease has a broad clinical spectrum and remains undetected for years. Among subclinical deficiency states, attribuable to coeliac enteropathy, combined iron and folic acid malabsorption is predominant. An unexplained recurrent iron anaemia is an indication for small intestinal biopsy. Gastro-intestinal disorders are present in only 50 % of the cases. Coeliac disease is frequently associated with other major histocompatibility complex (MMC) -linked diseases which are mediated by immunological mechanisms: dermatitis herpetiformis, oral ulcerations, IgA nephropathy, rheumatoid arthritis, sarcoidosis. Dermatitis herpetiformis is a useful model for examination of the spectrum of mucosal changes that typify gluten sensitivity and subliminal lesions without villous atrophy. An increased interest is devoted to the intra-epithelial T-lymphocyte population, not only in the small intestine, but at the level of the stomach and the colon. A "rectal challenge" test has been proposed for detecting gluten sensitivity in coeliac patients. Such a test could be an original method of screening, reducing so the need of small intestinal biopsy. The preliminary results are to be confirmed. Until now, jejunoscopy remains mandatory for the diagnosis and the survey of intestinal lesions related to coeliac disease

A parallel, implicit, multi-dimensional upwind, residual distribution method for the Navier-Stokes equations on unstructured grids

A multi-dimensional cell-vertex upwind discretization technique for the Navier-Strokes equations on unstructured grids is presented. The grids are composed of linear triangles in two and linear tetrahedra in three space dimensions. The nonlinear upwind schemes for the inviscid part can be viewed as a multi-dimensional generalization of the Roe-scheme, but also as a special class of Petrov-Galerkin schemes. They share with these schemes a compact Galerkin stencil, and are in addition monotonic by construction. The Petrov-Galerkin interpretation of the discretization technique allows a straightforward extension to the Navier-Strokes equations. For linear elements this boils down to a Galerkin discretization for the viscous terms. Compared to standard finite-volume methods on these grids, the method shows an increased accuracy, which becomes comparable with structured grid algorithms. The spatially discretized set of equations is integrated in time using the Backward Euler time integration method. The full Jacobian matrix is computed, either numerically by finite differences or approximated analytically, and stored. The resulting set of linear equations is solved by a Block MILU(0) preconditioned Krylov subspace method. For this purpose the Aztec library of SANDIA National Laboratories is used, which also takes care of the parallelization process and completely hides the details for the user. Results are presented for a two-dimensional turbulent shock wave boundary layer interaction in a nozzle and the turbulent flow over an ogive cylinder. All computations have been performed on the Cray T3E of the Technical University of Delft.info:eu-repo/semantics/publishe

[Neurofibromatosis Type-i (recklinghausens Disease) Associated With Abdominal Neurofibrosarcoma and Pheochromocytoma - Case-report]

Neoplasia and endocrine disorders are common complications of neurofibromatosis 1 (NF1 - von Recklinghausen disease). We report here a case of NF1 in a 31-year-old woman presenting simultaneously with an abdominal neurofibrosarcoma and a pheochromocytoma. The prevalence of secondary neoplasia and endocrine tumors in NF1 is also discussed

Numerical study of elemental demixing in atmospheric entry flow regimes near local thermodynamic equilibrium

We apply a recently derived and explicitly closed form of the equations of chemically reacting flows under local thermodynamic equilibrium to investigate its applicability to hypersonic flows. This new model rigorously takes into account the effects of the separation of chemical elements due to the differential diffusion of species, known as elemental demixing. We study the particular case of a neutral 5-species air flow around a blunt body configuration, with realistic free stream conditions corresponding to the later stages of a re-entry trajectory of a future space mission. In order to assess to what extent the local equilibrium assumption holds for the consider physical problem, we compare our results with other ones obtained using a chemical non-equilibrium model. Particular attention is paid to the distribution of oxygen elements in the flow field