Year: 2021
Type: preprint
Abstract: Flow computation in complex geometries, such as buildings for example, is challenging at several levels including for instance mesh generation and presence of small elements (doors, windows) that need spatial resolution. When compressible effects are present, such as those resulting from explosions, choking conditions may appear in geometric restrictions. Pressure relaxation to atmospheric condition with existing CFD solvers consequently requires resolved 3D computations, that may be tremendously expensive. In the present work under-resolved computations are addressed, meaning that large computational cells and large time steps are used. Typically, cells’ size is of the order of rooms’ size. Consequently, special care must be taken at geometric discontinuities. This issue is reminiscent of flow computation with discontinuous area change (Le Floch and Thanh, 2003, Andrianov and Warnecke, 2004, Kroner and Thanh, 2005, Thanh, 2009, Han et al., 2012, to cite a few). However, in the present context, both simplifications and complexities appear. On one hand, full Riemann problem solution is not needed, only flux computation is required resulting in significant simplifications. On the other hand, the flow is 3D, meaning that related complexities must be considered, in the frame of unstructured grids. A fast, efficient, and accurate method is developed for such flows. It consists of two steps. The first step deals with a simple and fast mesh generation where no geometric detail, such as a door for example, is needed. Only “footprints” of the 3D geometry are required. The second step deals with a simple, fast and specific Riemann solver that addresses the previously omitted geometric restrictions directly in the solution states and through the flux distribution as well. The proposed method then appears very convenient when hazardous and pressing situations are involved and require knowledge of the pressure fields. It is validated against resolved computations. Examples are shown with 3D computations of a realistic building.
Source: HAL
Authors: Chiapolino, Alexandre, Fraysse, François, Saurel, Richard
Institution: Laboratoire de Mécanique et d’Acoustique
Language: English
Subfield: Computational Mechanics
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W4226038332