Automated moving mesh techniques and re-meshing strategies in CFD applications using morphing and rigid motions

Report on activity presented to RAS.The presence of moving meshes when motions of fluids and solids are being simulated requires a good control of the topological deformations that can take place both into the surface mesh and into the volume cells. The work done in getting the control of the mesh morphing techniques in CFD applications of fluid-structure interactions and rigid bodies motions is here presented. The effects of imposed rigid body motions on a fluid mesh surrounding or surrounded by a solid body are analysed. Surface boundary mesh extraction and CAD geometry updating strategies for the preservation of a good quality mesh during the calculation are investigated and developed. Java programming is employed in order to automate the process of re-meshing to avoid degeneration

Automated moving mesh techniques in CFD. Application to fluid-structure interactions and rigid motions problems

Collana seminari interni 2012, Number 20120411.In the Computational Fluid Dynamics (CFD) simulation codes, the physical domain is divided into a finite number of small control volumes, corresponding to the cells of a computational grid, where discrete versions of the integral form of the continuum transport equations are applied. For the simulation of the moving meshes (fluids or solids), we employ specific morphing techniques combined with rigid motions. Since morphing strategies can easily lead to poor quality cells, it becomes important to keep under control the topological deformations that can take place both into the surface mesh and into the volume cells, by means of specific mesh quality metrics and re-meshing procedures. The work done in getting the control of the morphing/re-meshing techniques in order to use them in applications that principally treat with fluid-structure interactions and rigid bodies motions is here presented. In such applications, when local deformations of surfaces occur, bad topological effects like warped, twisted or self-intersected faces can easily lead to the appearance of negative volume cells, determining the simulation to stop running. We give a demonstration of how various morphing techniques have been applied to simulations that especially treat with structural and moving parts, in particular, in cases where the deformations arise from considerations related to solid displacements and stresses (pipe's walls vibrations) or to rigid body motions (translations). Surface boundary mesh extraction and CAD geometry updating strategies to avoid mesh degeneration are investigated and developed. Java programming is employed for the automation of the re-meshing procedures

Re-meshing strategies in CFD simulations of moving meshes

Misc - august 2012.The presence of moving meshes when motions of fluids and solids are being simulated requires a good control of the cells topological deformations. The work done in getting the control of the mesh morphing techniques in Computational Fluid Dynamics (CFD) applications of fluid-structure interactions and rigid bodies motions is here presented. The effects of imposed rigid body motions on a fluid mesh surrounding a solid body are analysed and strategies for maintaining a reasonable quality mesh during its deformation are investigated and developed. Java programming is employed in order to automate the process of re-meshing when the mesh deformation is dangerously close to the degeneration

Sugli spazi omogenei di dimensione tre SO(2) - isotropi

In this thesis we studied some problems from the theory of the submanifolds of the three-dimensional Riemannian manifolds. Our intention is to evaluate which properties of the submanifolds depend by the dimension of the group of isometries. We considered a two-parameter family of three-dimensional Riemannian manifolds (M, ds2 ℓ,m), endowed with the Cartan - Vranceanu metrics. These metrics can be found in the classification of 3-dimensional homogeneous metrics given by L. Bianchi. Their geometric interest lies in the following fact: the family of metrics includes all 3-dimensional homogeneous metrics whose group of isometries has dimension 4 or 6, except for those of constant negative sectional curvature. The group of isometries of these spaces has a subgroup isomorphic to the group SO(2), so there exist surfaces of revolution around z-axis. We explicitly obtained the Lie algebra of the Killing vector fields and thus the group of isometries for the C-V metrics. We determined the equations of the geodesics using the Killing vector fields and obtain explicitly the equation of the surface which con- tains the geodesics. After having determined the totally geodesics surfaces isometrically immersed in the C-V spaces, we studied the totally umbili- cal submanifolds of these spaces, proving that the only totally umbilical submanifolds are totally geodesic. We found the geodesics for the SO(2)- invariant surfaces of the Cartan-Vranceanu spaces, deduced the conditions that meridians and parallels must satisfy in order to be geodesics and show the analogies with the euclidian case