This paper presents an evolutionary structural topology optimization method for the design of completely submerged buoyant modules with design-dependent fluid pressure loading. This type of structure is used to support offshore rig installation and pipeline transportation at all water depths. The proposed optimization method seeks to identify the buoy design that has the highest stiffness, allowing it to withstand deepwater pressure, uses the least material and has a minimum prescribed buoyancy. Laplace's equation is used to simulate underwater fluid pressure, and a polymer buoyancy module is considered to be linearly elastic. Both domains are solved with the finite element method. Using an extended bi-directional evolutionary structural optimization (BESO) method, the design-dependent pressure loads are modelled in a straightforward manner without any need for pressure surface parametrization. A new buoyancy inequality constraint sets a minimum required buoyancy effect, measured by the joint volume of the structure and its interior voids. Solid elements with low strain energy are iteratively removed from the initial design domain until a certain prescribed volume fraction. A test case is described to validate the optimization problem, and a buoy design problem is used to explore the features of the proposed method.

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This article presents an evolutionary topology optimization method for mean compliance minimization of structures under design-dependent viscous fluid flow loads. The structural domain is governed by the elasticity equation and the fluid by the incompressible Stokes flow equations. When the modelling of a system consists in the interaction of multiple domains, the classic density-based topology optimization methods become arduous within the framework of dealing with the moving multi-physics loads and interfaces, due to the considerable volume of intermediate density elements. Herein it is suggested an alternative methodology to handle this type of loading problems. With an extended Bi-directional Evolutionary Structural Optimization (BESO) method, design-dependent Stokes flow loads are modelled straightforward during the optimization procedure. The discrete nature of the method allows both fluid and structural domains to be modelled separately in each step of the optimization. In order to validate the methodology, only small structural displacements and a simple staggered fluid-structure interaction algorithm are considered in this paper. Primary results are shown for a 2D flexible structure immersed in an incompressible viscous flow channel.@en

This paper presents an evolutionary topology optimization method for applications in design of completely submerged buoyant devices with design-dependent fluid pressure loading. This type of structures aid rig installations and pipeline transportation in all water depths in offshore structural engineering. The proposed optimization method seeks the buoy design that presents higher stiffness, less material and a prescribed buoyancy effect. A hydrostatic fluid is used to simulate the underwater pressure and the polymer buoyancy module is considered linearly elastic. Both domains are solved with the finite element method. From the initial design domain, solid elements with low strain energy are iteratively removed until a certain prescribed volume fraction. The studied case consists in a buoy for supporting subsea oil pipelines, in which the inner diameter is constant and the outer shape and interior holes are defined by the optimization algorithm. A new buoyancy constraint is introduced in order to guarantee a satisfactory buoyancy effect.@en