Topology optimization of passively moving rigid bodies in unsteady flows

Fuente: arXiv
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Main Authors: Tanabe, Yuta, Yaji, Kentaro, Ushijima, Kuniharu
Format: Preprint
Published: 2026
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author Tanabe, Yuta
Yaji, Kentaro
Ushijima, Kuniharu
author_facet Tanabe, Yuta
Yaji, Kentaro
Ushijima, Kuniharu
contents This study proposes the topology optimization method for moving rigid bodies subjected to forces from fluid flow, such as sails and turbines, with an unsteady time-dependent formulation. Unlike existing topology optimization frameworks in which rigid-body motion drives the flow, which is referred to as $\textit{active}$, the present study considers rigid-body motion induced by fluid forces, i.e., $\textit{passive}$. The equations of motion governing the rigid-body dynamics are solved in a coupled manner with the continuity equation and the momentum conservation equations. The rigid body is represented on a design grid that is separated from the analysis grid on which the state and adjoint fields are defined. After updating the rigid body motion, the body is mapped onto the analysis grid. The fluid equations are solved using the lattice kinetic scheme, an extended version of the lattice Boltzmann method, owing to its suitability for unsteady flows. Design sensitivities based on the adjoint variable method are presented and applied to two- and three-dimensional problems involving translational and rotational motions. The optimized shapes for each problem are discussed from a physical perspective and compared with a reference shape or their binarized counterparts, providing insights into the effectiveness of the proposed method as well as its limitations.
format Preprint
id arxiv_https___arxiv_org_abs_2601_18272
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Topology optimization of passively moving rigid bodies in unsteady flows
Tanabe, Yuta
Yaji, Kentaro
Ushijima, Kuniharu
Fluid Dynamics
Optimization and Control
This study proposes the topology optimization method for moving rigid bodies subjected to forces from fluid flow, such as sails and turbines, with an unsteady time-dependent formulation. Unlike existing topology optimization frameworks in which rigid-body motion drives the flow, which is referred to as $\textit{active}$, the present study considers rigid-body motion induced by fluid forces, i.e., $\textit{passive}$. The equations of motion governing the rigid-body dynamics are solved in a coupled manner with the continuity equation and the momentum conservation equations. The rigid body is represented on a design grid that is separated from the analysis grid on which the state and adjoint fields are defined. After updating the rigid body motion, the body is mapped onto the analysis grid. The fluid equations are solved using the lattice kinetic scheme, an extended version of the lattice Boltzmann method, owing to its suitability for unsteady flows. Design sensitivities based on the adjoint variable method are presented and applied to two- and three-dimensional problems involving translational and rotational motions. The optimized shapes for each problem are discussed from a physical perspective and compared with a reference shape or their binarized counterparts, providing insights into the effectiveness of the proposed method as well as its limitations.
title Topology optimization of passively moving rigid bodies in unsteady flows
topic Fluid Dynamics
Optimization and Control
url https://arxiv.org/abs/2601.18272