Generalized Internal Boundaries (GIB) for Large Deformations

During the last year, the GIB framework has been extended to model moving objects. GIB is very powerful in applications with large motions such as topology optimization, tire simulation, 6DoF etc. Currently, in these applications, the mesh motion algorithm moves the boundaries until re-meshing is required. This method, in most industrial applications, is inefficient or infeasible. Using GIB, the point coordinates of the faces near the interface are snapped on the interface. After the snapping, a faceZone which contains the faces which are located exactly on the interface is constructed. A new boundary is created based on the faceZone and boundary conditions are applied. All the required operations for the GIB treatment are parallelized and they dont increase the computational cost. For static boundaries, the matrix contributions of each OpenFOAM R operator (fvm ::, fvc ::) using GIB and body fitted meshes are the same which guarantees that the results will be identical. For moving boundaries, a mechanism for proper treatment of the freshly fluid/solid cells has been developed. This mechanism is based on the Arbitrary Lagrangian-Eulerian (ALE) Method and guarantees the conservation of the quantities. The implementation is generic and no additional numerical schemes or executables are required.

The GIB framework is coupled with the in-house topology optimization engine helyxAdjoint. A simple application is presented in Figures 1a,1b. The sensitivities calculated based on the continuous adjoint method are used as a deformation displacement, which drives the interface towards the local minimum/maximum.

The last years, the automotive industry is interested in the accuracy of the tire simulation. It is known that the tires are causing the 30% of the total drag force of a car. As a result, it is very important to simulate the rotating tires are accurate as possible. This means that the treads and the deformation of the tires have to been taken into consideration. Existing approaches using solid tires with rotating wall velocity or rotating wheels with AMI interfaces have been used in the past to improve accuracy. However, all the existing techniques have accuracy and/or performance limitations. In this paper, the GIB are used to simulate the rotation and the deformation of the tires.

Two applications of tire simulations are presented (Figures 2a 3a). In these applications, the tire geometries, which are described as an stl format, are provided to the GIB framework. The motion of the tire is specified from the existing solid body motion functions of OpenFOAM.