Since 1861, RINA engineers have been perfecting the art of product development for the aerospace & defence, energy, industry, transportation, marine and biomedical sectors. Along the way, they have adopted some simulation meshing tips and tricks that speed up product development.
As an example, RINA engineers know that a small change in a turbine’s blade design may influence its structural response and aerodynamics. Therefore, quickly predicting how a redesign affects a blade is crucial for innovation and improved product reliability.
However, exploring the effects of design changes can be time-consuming. This is because engineers often create a new geometry, mesh and simulation for each iteration.
Instead, RINA takes advantage of ANSYS Mechanical and the radial basis functions (RBF) Morph add-on to run through a blade’s design space quickly and efficiently.
RBF Morph Promises Faster Mesh Alterations and Product Development
Using RBF Morph, engineers can alter a portion of the geometry of a blade, without repeating the meshing and simulation process.
The RBF Morph feature can also be used in an optimization workflow within Mechanical. The feature automatically alters the mesh through a range of shapes to determine the optimal configuration of the component.
RBF Morph does this by using a single mesh as a starting point and morphing it into new geometries that are ready to be studied. The feature allows engineers to change the locations of nodes in the current computational mesh, so it matches the surface and volume of a new shape.
By eliminating the need to create new geometries, meshes and simulations, RBF Morph makes the redesign process more efficient. Additionally, since morphing a mesh can be done in seconds, and because the simulation can be started from the previous convergence point — instead of running it from the beginning — engineers can save time and money on product development.
Applying RBF Morph to a Blade Fillet Redesign
Recently, RINA’s engineers faced the challenge of modifying the curved fillet region at the root of a turbine blade. The aim of this redesign was to reduce the stress concentration and increase the service life of the blade by limiting fatigue.
Using Mechanical — with a mesh comprising 430,000 nodes, 300,000 second-order tetrahedral elements and mesh refinement at hot spots — the engineers calculated a maximum principal stress of about 195 MPa.
As expected, the stress peak occurred close to the point where the cross section has an important geometrical variation. By adopting a larger radius at the root of the fillet, the engineers were able to smooth out the force and reduce peak stress.
RBF Morph Processes the Simulation Mesh in Mechanical
The full RBF Morph process involved varying the positions of two curves that controlled the shape of the fillet.
The mesh’s nodes were then extracted to follow the new shape of the fillet.
RINA’s engineers specified how the nodes could move as the mesh’s volume morphed along the new curves. They were also able to define nodes that were kept fixed during the morph.
With the right inputs, the engineers were able to control morphing process so the volume and surfaces deformed smoothly and properly.
Ultimately, 125,000 nodes were updated in just 15 seconds to accommodate the deformation without excessively degrading the quality of the mesh.
Product Development and Optimizations using RBF Morph
After establishing a consistent RBF Morph procedure, RINA’s engineers carried out a two-parameter optimization of the fillet control points using response surface methods, design of experiments (DoE) and parallel plots.
These optimization tools allowed the engineers to identify an optimal blade design where the stress was spread out and had a smaller peak.
RINA’s engineers saw a substantial stress reduction of 22.5 percent in the optimal blade design.
The team was quite satisfied with the results.
RINA’s engineers found that using RBF Morph was intuitive, effective and fast. They noted that the tool was familiar because it shares the same scoping methods, working environment and philosophy of Mechanical. They noted that the RBF Morph technology was a natural extension of the finite element method (FEM) solver.
RINA now includes the RBF Morph technology into its design processes so it can develop better solutions faster.