Hydroelastic simulation of the acoustic behaviour of ship-propeller configurations with and without cavitation

近年来，船舶对海洋的噪声污染引起了有关部门的高度重视。预计造船业将不得不采取相应的行动-已经在设计阶段-为了减少噪音，也符合相应的法规，预计在不久的将来。开发了一种数值模拟方法，允许在项目的第一阶段对柔性船用螺旋桨的声学特征进行详细调查，我们的目标是在该项目的第二阶段的优化算法的范围内采用这种方法。开发分区耦合的边界元（流体子问题）和高阶有限元（结构子问题）结合声学评估的基础上的Ffowcs威廉斯-霍金方程产生非常有效的模拟。然而，完全耦合的解决方案的方法仍然是太昂贵，直接用于优化的目的。因此，第二阶段的重点在于开发一个适当的优化过程，其中包括解耦模拟，这将大大减少计算时间。此外，我们计划考虑复合材料，因为它们在设计具有被动自适应变形行为的螺旋桨时提供了更高的灵活性，从而降低了辐射噪声。因此，我们的目标是多阶段优化过程，其中在第一阶段，使用非耦合流体动力学模拟来找到螺旋桨的最佳变形形状，而无需实际考虑其动态行为。在第二阶段，应使用非耦合结构模拟来找到初始螺旋桨配置（形状和复合结构），当施加水动力载荷时，该配置产生第一阶段的变形形状。这两个阶段产生适当的初始猜测的最后阶段，耦合流固耦合模拟用于进一步优化初始螺旋桨配置。

Recently, noise pollution in the oceans due to ships has raised a lot of attention from the corresponding authorities. It is expected that the shipbuilding industry will have to take according actions - already at the design stage - for the sake of noise reduction, and also to comply with respective regulations that are expected in the near future.Having developed a numerical simulation approach that allows for a detailed investigation of the acoustic signature of flexible marine propellers in the first phase of the project, we aim to employ this approach in the scope of an optimization algorithm in the second phase of the project. The developed partitioned coupling of boundary elements (for the fluid sub-problem) and high-order finite elements (for the structural sub-problem) in combination with an acoustic evaluation based on the Ffowcs Williams-Hawking equation yields very efficient simulations. However, the fully coupled solution approach is still too costly to be used directly for optimization purposes. Accordingly, the focus of the second phase lies on the development of a suitable optimization process that incorporates uncoupled simulations, which will greatly reduce the computation time. Further, we plan to consider composite materials, as they offer a higher flexibility when designing propellers with passively adaptive deformation behavior that reduces the radiated noise.Accordingly, we aim at a multi-stage optimization process, where in a first stage, uncoupled hydrodynamic simulations are used to find optimal deformed shapes for propellers without actually considering their dynamic behavior. In a second stage, uncoupled structural simulations shall be used to find an initial propeller configuration (shape and composite structure), which yields the deformed shapes from the first stage when the hydrodynamic loads are applied. These two stages yield suitable initial guesses for a final stage, where coupled FSI simulations are used to further optimize the initial propeller configuration.