EnginSoft - Conference Abstracts

EnginSoft International Conference 2009
CAE Technologies for Industry

RBF Morph: a fast meshless morpher for Fluent

Biancolini Marco Evangelos - RBF Morph

Abstract

Meshless, embedded and fast are the best keywords for describing the new tool for FLUENT, RBF Morph, a unique morpher that combines a very accurate control of the geometrical parameters with an extremely fast mesh deformation, fully integrated in the CFD solving process. RBF Morph is the meeting point between state-of-the-art scientific research and top-level industrial needs. RBF Morph is meshless because it uses Radial Basis Functions (RBF), one of the most powerful interpolation method available. RBF are able to interpolate everywhere in the space a function defined at discrete “control” points, where it always returns the exact prescribed value. An arbitrary deformation field can be defined and applied on any possible mesh structure and strategy, e.g. any combination of tetrahedron, hexahedron, generic polyhedra, prisms, hexcore, non-conformal interfaces, etc.). Furthermore it simply acts on node locations and parallel calculation is therefore naturally defined. RBF Morph is embedded because the entire set-up is done inside Fluent, thanks to a comprehensive GUI that allows to define the morphing problem interacting with Fluent entities. Moreover TUI commands are also available to drive the morpher by means of simple scripts. A suite of custom UDF functions, linked to a proprietary fast solver, builds the numerical kernel of the application. RBF Morph is fast because it was born to satisfy the top-level industrial needs of morphing very large models (of the order of hundreds of millions cells), with the aim to study the effect of slight modifications without rebuild the mesh. Most important industrial requirements, like process integration, mesh-independent solution, parallelism, large models and arbitrary mesh element type management, are so fulfil by RBF Morph. The final goal of RBF Morph is to perform parametric studies of component shapes and positions typical of the fluid-dynamic design like design developments, multi-configuration studies, sensitivity studies, DOE (Design Of Experiment) and shape optimization. Thanks to the ANSYS partnership this product is now available for FLUENT users as an addon. The working principles are better explained through an industrial application (already submitted to ANSYS EASC 2009): the optimisation of a motorbike windshield. Three modifiers are used to change the original CFD model acting on driver height, driver position and deflector angle. The setup stage for changing driver angle starts with the definition of an encapsulation box. The number of points located on the surface is defined imposing a proper point spacing. The effect of encapsulation is to give a near zero solution on the boundary and to apply the morph only to the mesh nodes that fall inside the encapsulation domain. To complete the set-up two more sets of source points are required: the first one is composed by all the mesh nodes that belong to the helmet, the second one is composed by all the nodes on the bike and on the windshield. For the first set, a rotation about the driver ankles is prescribed; for the second a zero rigid movement is imposed to preserve the original shape. The remaining nodes that fall inside the domain remain free to deform under the action of the morpher. The others modifiers can be defined (and stored) in a similar fashion. The interaction between modifiers has of a simple script that exploits the new parametric nature of the FLUENT model.