Initialization of high‐order accuracy immersed interface CFD solvers using complex CAD geometry

Abstract

Summary This study concerns the development of a numerical methodology for initializing immersed interface‐based CFD solvers for using complex computer‐aided design (CAD) geometry. CFD solvers with higher‐order discretization stencils require larger stencil widths, which become problematic in regions of space where insufficient mesh resolution is available. This problem becomes especially challenging when convoluted triangulated surface meshes generated from complex solid models are used to initialize the cut‐cells. A pragmatic balance between desired local geometry resolution and numerical accuracy is often required to find a practical solution. Here, a robust iterative fill algorithm is presented that balances geometry resolution with numerical accuracy (via stencil size). Several examples are presented to illustrate the use of this initialization procedure that employs both the original CAD generated triangulated surface mesh, along with a level set representation of the surface to initialize cut‐cells and boundary proximity measures for creation of CFD stencils. Convergence error analysis of surface area and enclosed volumes is first presented to show the effects of fill on the geometry as a function of desired stencil size and grid resolution. The algorithm is then applied to geometrically complex problems using large eddy simulation. Two problems are considered. The first is flow around the Eiffel Tower. The second is a combustion swirler in the context of a design problem. Copyright © 2016 John Wiley & Sons, Ltd.

Anisotropic adaptive body-fitted meshes for CFD

“…The interface of the immersed object is determined by the zero-value of φ (Figure 1). Further details on how to compute the signed distance function can be found in [20,23,36,39].…”

“…1. inserting local nodes at the interface 2. increasing the size of the discrete stencils near the interface 3. adding nodes in the solid region in the vicinity of the interface to enforce local boundary conditions Other methods rely on transforming the background mesh to conform to the boundary by using a closest point projection to parameterize the immersed boundary over a collection of nearby edges [42], or on augmenting the level-set function via an iterative procedure to then reconstruct the cut cell elements using Lagrangian polynomials [23].…”

Collaborative Multidisciplinary Design Optimization for Conceptual Design of Complex Products

“…Nowadays, there is a strong connection between CAD and CFD tools to exchange geometric models. Similar to CAD, CFD also benefits significantly from parameterization (Chawner et al, 2016;Vasilopoulos et al, 2016;DesJardin et al, 2016). There are many commercial CFD tools available, for example ANSYS Fluent (Fluent, 2016), Star-CCM+ (CD-adapco, 2016), and IESVE Mcroflo (Microflo, 2016).…”