Academic literature on the topic 'Conforming triangulation'

Abstract An implicit finite volume approximation of the Navier-Stokes equations governing compressible, viscous flow in the presence of moving boundaries will be described. The method is incorporated in the DLR-r-Code, uses a box-type discretisation and works on general conforming triangulations. The discretisation of the convective fluxes is accomplished by means of an approximate Riemann solver used with linear ENO recovery while the diffusive fluxes are discretised in a central manner. The AUSMDV scheme developed by Liou and Wada [5] is chosen as the Riemann solver in an implicit formulation in the presence of moving grids for the first time.

This article explores the ability of a decision support system (DSS) to improve the quality of decision making in extreme environment. This DSS is actually based on a networked information system. Academic literature commonly mentions models of fit to explore the relationship between technology and performance, reckoning users' evaluations as a relevant measurement technique for Information System (IS) success. Although effective contributions have been achieved in measurement and exploration of fit, there have been few attempts to investigate the triangulation of fit between “Task-DSS-Decision Maker” under stressful and uncertain circumstances. This article provides new insights regarding the advantages provided by networked IS for making relevant decisions. An original case study has been conducted. It is focused on a networked decision support system called Link 16 that is used during aerial missions. This case study shows that the system improves decision making on an individual basis. Our result suggest the importance of three main fit criteria – Compliance, Complementarity and Conformity – to measure DSS performance under extreme environment and display a preliminary decisional fit model.

Abstract The generation of high-quality computational grids for complex aerodynamic configurations remains an important area of concern, hindering the routine application of Computational Fluid Dynamics (CFD). The block-structured approach has proved to be highly successful, but it does in general require extensive user intervention and expertise. Alternatively, unstructured grids can be made to fit very complex geometries in a relatively straightforward manner and has been shown to be highly effective for grid adaptivity[4]. Therefore, much progress has been made over the past few years to develop fast and robust unstructured grid generators. Two well-known approaches commonly used for construction of triangular unstructured grids are the Delaunay criterion and the advancing front method. The Delaunay triangulation, although it has many interesting properties [7] does not address the issues of grid point creation and boundary conformity. Additionally this method is not naturally capable of generating high aspect ratio cells required for viscous flow calculations. The advancing front method has received much attention, particularly because of its self-sufficiency and grid quality ([1],[4]). However, special care must be taken when choosing the data structure to efficiently perform the relevant searches.

Abstract Combining the Perpendicular Bisector (PEBI) grids with the Two Point Flux Approximation (TPFA) scheme demonstrates a potential to accurately model on unstructured grids, conforming to the geological and engineering features of real grids. However, with the increased complexity and resolution of the grids, the PEBI conditions will inevitably be violated in some cells and the approximation properties will be compromised. The objective is to develop accurate and practical grid quality measures that quantify such errors. We critically evaluated the existing grid quality measures and found them lacking predictive power in several areas. The available k-orthogonality measures predict error for flow along the strata, although TPFA provides an accurate approximation. The false-positive results are not only misleading but can overwhelm further analysis. We developed the so-called "truncation error" grid measure which is probably the most accurate measure for flow through a plane face and accurately measures the error along the strata. We also quantified the error due to the face curvature. Curved faces are bound to exist in any real grid. The impact of the quality of the 2-D Delaunay triangulation on TPFA approximation properties is usually not taken into account. We investigate the impact of the size of the smallest angles that can cause considerable increase of the condition number of the matrix and an eventual loss of accuracy, demonstrated with simple examples. Based on the analysis, we provide recommendations. We also show how the size of the largest angles impacts the approximation quality of TPFA. Furthermore, we discuss the impact of the change of the permeability on the TPFA approximation. Finally, we present simple tools that reservoir engineers can use to incorporate the above-mentioned grid quality measures into a workflow. The grid quality measures discussed up to now are static. We also sketch the further extension to dynamic measures, that is, how the static measures can be used to detect change in the flow behavior, potentially leading to increased error. We investigate a comprehensive set of methods, several of them new, to measure the static grid quality of TPFA on PEBI grids and possible extension to dynamic measures. All measures can be easily implemented in production reservoir simulators and examined using the suggested tools in a workflow.

Immersed boundary methods have been widely used for simulating flows with complex geometries, as quality boundary-conforming grids are usually difficult to generate for complex geometries, especially, when motion and/or deformation is involved. Complex geometries can be conveniently represented using triangulated surfaces in a Lagrangian manner. A major task in immersed boundary simulations is to inject the immersed boundary information into the background Cartesian grid, such as the inside/outside status of a grid point with regard to the immersed boundary and the accurate sub-cell position of the immersed boundary for a grid point next to it. For high resolution simulations with moving/deforming boundaries, this step can be very expensive. In this paper, a simple, fast, and robust procedure is developed for setting up complex triangulations. Several cases with complex geometries are performed to demonstrate the efficiency and robustness.