Propulsion bioinspirée par hélice : reconfiguration et intermittence

This experimental thesis focuses on propeller propulsion through two new bio-inspired concepts: reconfiguration and intermittency. Reconfiguration involves making structures flexible to adapt to flow conditions. Previous results have shown that this deformation can be exploited to passively adapt to changing external conditions if the flexibility is appropriately chosen. This ability to change shape can also be exploited dynamically through intermittent propulsion, a strategy adopted by many fish and bird species to reduce the cost of locomotion.The work presented here initially addresses the fluid-structure interaction problem of a propeller with flexible blades in a water flow. We highlight the laws governing the blade de- formation during the rotation. These deformations modify the efficiency of propulsion, and a propeller with flexible blades can be made more resilient to velocity variations compared to its rigid version.Next, we investigate intermittent propulsion, which involves alternating active and passive propulsion phases to reduce energy costs. In our case, this means periodically rotating the propeller. For intermittent propulsion to be effective, it is crucial to reduce the drag force acting on the boat during the passive phase. By using a propeller that can passively open and close, we demonstrate that propulsion costs can be reduced by 25% compared to continuous propulsion at the same speed.This experimental thesis focuses on propeller propulsion through two new bio-inspired concepts: reconfiguration and intermittency. Reconfiguration involves making structures flexible to adapt to flow conditions. Previous results have shown that this deformation can be exploited to passively adapt to changing external conditions if the flexibility is appropriately chosen. This ability to change shape can also be exploited dynamically through intermittent propulsion, a strategy adopted by many fish and bird species to reduce the cost of locomotion.The work presented here initially addresses the fluid-structure interaction problem of a propeller with flexible blades in a water flow. We highlight the laws governing the blade de- formation during the rotation. These deformations modify the efficiency of propulsion, and a propeller with flexible blades can be made more resilient to velocity variations compared to its rigid version.Next, we investigate intermittent propulsion, which involves alternating active and passive propulsion phases to reduce energy costs. In our case, this means periodically rotating the propeller. For intermittent propulsion to be effective, it is crucial to reduce the drag force acting on the boat during the passive phase. By using a propeller that can passively open and close, we demonstrate that propulsion costs can be reduced by 25% compared to continuous propulsion at the same speed