Optimizing Fluid–Structure Interaction Systems with Immersogeometric Analysis
This work presents an FSI design optimization framework and applies it to improving the structural performance of a water brake used to stop aircraft landing on short runways. Inside the water brake, a dissipative torque is exerted on a rotor through interactions between rotor blades and a surrounding fluid. We seek to optimize blade shape over a parameterized design space, to prevent potentially-damaging stress concentrations without compromising performance. To avoid excessive numbers of costly simulations while exploring the design space, we use a surrogate management framework that combines derivative-free pattern search optimization with automated construction of a low-fidelity surrogate model, requiring only a handful of high-fidelity FSI simulations. We avoid the difficult problem of generating fluid and structure meshes at new points in the design space by using immersogeometric FSI analysis. The structure is analyzed isogeometrically––its design geometry also serves as a computational mesh. This geometry is then immersed in an unfitted fluid mesh that does not depend on the structure’s design parameters. We use this framework to make significant improvements to the baseline design.
Top: The NURBS-based parametric model of the water twister and a cut through the unfitted fluid mesh used in immersogeometric analysis. Note that changes to the structural design do not require any fluid mesh regeneration. Bottom: Design modification strategy used for rotor blades and stator vanes. x1, x2 and x3 are the design variables.
The immersogeometric simulation results are in excellent agreement with the reference boundary-fitted simulation results as well as the experimental data.
By performing immersogeometric FSI simulations and searching through the design space, a new design which reduces the stress variance by 35% is found.
Contours of von Mises stress on FSI-based optimization result. The deflection is scaled by 100 times.
Parametric Design and Optimization using Isogeometric Analysis
Isogeometric analysis (IGA) fundamentally seeks to bridge the gap between engineering design and high-fidelity computational analysis by using spline functions that are typically used in CAD as finite element bases. In this work, we propose a novel approach that employs IGA methodologies while still rigorously abiding by the paradigms of advanced design parameterization, analysis model validity, and interactivity. The entire design lifecycle utilizes a consistent geometry description and is contained within a single platform. Because of this unified workflow, iterative design optimization can be naturally integrated. The proposed methodology is demonstrated through an IGA-based parametric design optimization framework implemented using the Grasshopper algorithmic modeling interface for Rhinoceros 3D. The framework is capable of performing IGA-based design optimization of realistic engineering structures that are practically constructed through the use of complex geometric operations. In addition to inherently featuring the advantageous characteristics of IGA, the seamless nature of the workflow instantiated in this framework diminishes the obstacles traditionally encountered when performing FEA-based design optimization. The effectiveness of the framework is demonstrated on a wind turbine blade design.
Parametric design and optimization of wind turbine blades using isogeometric analysis.
An interactive geometry modeling and parametric design platform for isogeometric analysis.