Parametric bird strike study of a transonic rotor using isogeometric analysis

This paper investigates the use of isogeometric analysis (IGA) to study high velocity impact on a transonic compressor rotor resulting from a bird strike. An approach is developed for creating volumetric NURBS blade models which are suitable for IGA. A newly implemented 3D solid NURBS element within the development version of LS-Dyna is validated against finite elements for the NASA rotor 37 under a steady centrifugal load. The smoothed particle hydrodynamics (SPH) method is then used to simulate impact from a bird strike. As a preliminary assessment for multi-disciplinary optimisation (MDO), with the objective to improve aerodynamic performance whilst satisfying mechanical constraints from impact, a number of different blade designs are created by modifying the NURBS control points directly. Hence the control points used in analysis can also be used in the design space. This approach eliminates the need for re-meshing, highlighting the advantages that IGA can bring to design optimisation, since without filtering, moving finite element nodes can result in non-smooth geometries. NURBS parametrisations are also more efficient resulting in fewer design variables, thereby accelerating the optimisation process. The effect of blade sweep, lean, twist and thickness on the impact response are investigated. The results in this paper show the promise that IGA holds in this field but some limitations of the current LS-Dyna implementation are also discussed.