Computer Aided Grid Interface: An Interactive CFD Pre-Processor

33rd Aerospace Sciences Meeting and Exhibit, 1995

Generating high quality, structured, continuous, body-fitted grid systems (multiblock grid systems) for complicated geometries has long been a most laborintensive and frustrating part of simulating flows in complicated geometries. Recently, new methodologies and software have emerged that greatly reduce the human effort required to generate high quality multiblock grid systems for complicated geometries. These methods and software require minimal input from the user-typically, only information about the topology of the block structure and number of grid points. This paper demonstrates the use of the new breed of multiblock grid systems in simulations of internal flows in Complicated geometries. The geometry used in this study is a duct with a sudden expansion, a partition and an array of cylindrical pins. This geometry has many of the features typical of internal coolant passages in turbine blades. The grid system used in this study was generated using a commercially available grid generator. The simulations were done using a recently developed flow solver, TRAF3D,MB, that was specially designed to use multibl0ck grid systems.

2009

Abstract We present a physically-based fluid simulation with dynamic grid refinement on parallel SIMD graphics hardware. The irregular and dynamic structure of an adaptive grid requires sophisticated memory access patterns as well as a decomposition of the problem for parallel processing and the distribution of tasks to multiple threads.

2018

Computer Aided Design tools (CAD) allow geometries to be constructed in software so they can be used in manufacturing (CAM), analysis (CAE), and measurement (CMM). For performing Computational Fluid Dynamics analysis (CFD), although a mesh can be constructed in certain cases from scratch in a meshing software, more often it is created and imported from a CAD software. Starting from a positive shape geometry, various steps in geometry simplification, negative volume extraction, meshing, and solving are described and illustrated in this paper. The two CAD software used in this study are Solidworks by Dassault Systèmes and DesignModeler by ANSYS Inc. Their usage, file transfer format, and the issue of surfaces vs. solids are illustrated in this paper through a geometry example. Other common problems such as being unable to generate a volume mesh or the mesh size is too large, are also presented and discussed. Finally, a successfully completed mesh is shown, along with its CFD computati...

High aspect-ratio grids are required for accurate solution of boundary layer and wake flow. An approach for the efficient generation of isotropic and stretched viscous unstructured grids is introduced in this paper. The proposed grid generation algorithm starts with a very coarse initial grid. In far field regions, isotropic cells of excellent quality are produced using a combination of point insertion and cell subdivision techniques. Simultaneously, a directional grid refinement strategy is used to construct highly stretched triangular cells in viscous dominated regions. First, anisotropic unstructured grids are produced in the stream-wise direction. Then, cells close to the solid surface are refined to highly stretched layer of triangles suitable for boundary layer region. The accuracy of the current grid generation approach is assessed by laminar and turbulent compressible flow solutions around NACA0012, RAE2822, and NHLP multi-element airfoils. Numerical flow simulation results are compared with published data. Comparisons point to accuracy of the proposed unstructured viscous grid generation procedure.

open Source CFD International …, 2008

This paper presents an implementation of the Generalized Grid Interface (GGI) for OpenFOAM. It is used to couple multiple non-conformal regions into a single contiguous domain at matrix level. The main advantage of the Generalized Grid Interface comes from ...

An existing Computational Fluid Dynamics (CFD) solver is parallelized by means of MPI. The solver includes a dynamic and adaptive grid generator for Cartesian Quadtree and Octree grids, which therefore also have to be parallelized. The grid generator generates grids fulfilling a specific set of rules, that have to be enforced also in parallel. The assembly of the large sparse matrices resulting from the implicit discretization of Navier-Stokes equations is done in parallel, as is the solving process. The parallel performance of both of these processes depends heavily on a good load balancing in order to reach satisfactory speedup. Two versions of load balancing are demonstrated, one based on block swapping, and the other by utilizing the Metis or Parmetis software packages for load balancing of graphs. Results are presented for load balancing and for the parallel speedup of solving the linear algebra system of equations.

International Journal of Computational Fluid Dynamics, 2019

Preprocessing remains one the main bottlenecks in the Computational Fluid Dynamics (CFD) simulations of flows involving complex geometries as advances in the algorithm development, turbulence modeling and parallel computing are made. To this end, two approaches are presented here to efficiently deal with complex geometries in order to reduce the preprocessing time and manual effort. First, a hybrid blocking approach, combining the medial axis based method with level set iso-surface is presented to aid the block topology generation for subsequent structured meshing of complex 3D external flow domains. Secondly, a hierarchical geometry handling approach is demonstrated which makes use of the lower order modeling, overset meshes and zonal blocking for efficient preprocessing. Typical external aerodynamics cases have been showcased to describe how such techniques can be used to address modern challenges in the preparation of complex geometries for flow simulations.

The Boeing Aero Grid and Paneling System (AGPS) is a programming language with built-in geometry features. Accessible through either a graphical user interface (GUI) or through a command line, AGPS can be used by operators with different levels of experience.

Airinnova is a start-up company with a key competency in the automation of high fidelity computational fluid dynamics (CFD) analysis. The goal of this SHAPE project, a collaboration with the PDC Center for High Performance Computing at the KTH Royal Institute of Technology (KTH-PDC), was to develop automated procedures for carrying out CFD analysis in the field of aerodynamic optimization and design. The project is a significant step towards automation of the core processes that ordinarily would require specialist skills, such as creation of the simulation mesh, thus assisting a broader sphere of engineers to design aircraft in more efficient and simpler ways.

In this paper, we present a hybrid grid generation approach for viscous flow simulations by marching a surface triangulation on viscous walls along certain directions. Focuses are on the computing strategies used to determine the marching directions and distances since these strategies determine the quality of the resulting elements and the reliability of the meshing procedure to a large extent. With respect to marching direction, three strategies featured with different levels of efficiencies and robustness performance are combined to compute the initial normals at front nodes to balance the trade-off between efficiency and robustness. A novel weighted strategy is used in the normal smoothing scheme, which evidently reduce the possibility of early stop of front generation at complex corners. With respect to marching distances, the distance settings at concave and/or convex corners are locally adjusted to smooth the front shape at first; a further adjustment is then conducted for fr...