Session: 06-07 Adaptive Systems in Robotics and Control

Paper Number: 164826

164826 - Bioinspired Active Vortex Generators for Enhanced Underwater Flow Control 

Seafaring vehicles can be subjected to flow separation at high incidence angles, resulting in hydrodynamic stall. The separation of flow from the wings results in the formation of vortex cores at the leading edge, which grow and move over the wing surface. The vortex cores eventually shed from the surface at the trailing edge, causing pressure fluctuations, thereby resulting in stalls. Stalls are highly undesirable as they can result in structural damage due to loss of control and maneuverability. Vortex Generators (VGs) have been widely used to control flow separation. However, existing VGs are usually static, and therefore, their configuration cannot be optimized to conform to changes in flow conditions. As a drawback, static VGs can sometimes induce parasitic drag if a particular static configuration does not match the stochastic nature of flows. Recently, dynamic VGs, otherwise called active VGs, were developed to mitigate the limitations of static or passive VGs. As the name implies, active VGs can be deployed on demand to match changes in flow conditions with the help of external actuation systems. The existing actuation systems for active VGs rely on hydraulic, shape memory, or plasma actuators, which are promising but also characterized by certain drawbacks. This study was proposed to overcome the limitations of existing active VG actuators. Inspired by the dermal papillae muscle of an octopus, which allows them to adapt to changes in flow conditions, we developed VGs powered by twisted spiral artificial muscles (TSAMs). TSAMs are manufactured from inexpensive materials such as polymer fishing lines and copper wires, shaped into a flat Archimedean spiral. TSAMs exhibit an out-of-plane vertical displacement, achieving a reversible extension of >2000% strain when electrothermally actuated with an input voltage of 0.2 V/cm for a few seconds, like how an octopus's skin protrudes in response to the contraction of the papillae muscles. This is an extension of our previous application of this device in aerodynamic flow separation control. For the underwater application, the TSAM and the entire control electronic components were mounted on a circuit board, making them more portable in contrast to our previous design. The hydrodynamic performance of the wing was determined using force-sensing equipment, while flow visualization was conducted to visually ascertain the effect of VGs in stall delay. The device was able to match the peak performance of static flow control devices at each angle of attack tested. Specifically, VGs deployed on demand by TSAMs produced a 25% to 30% increase in CL and an 8% to 10% drag reduction at high angles of attack compared to the clean hydrofoil. Precise displacement of TSAMs was achieved using an L1 adaptive controller together with the dynamic model guiding the electrothermal actuation of our TSAM.

Presenting Author: Rabiu Mamman Department of Mechanical Engineering, University of Iowa

Presenting Author Biography: Rabiu Mamman is a third-year PhD student in the Department of Mechanical Engineering at the University of Iowa. He holds a Bachelor's degree in Metallurgical and Materials Engineering and a Master's degree in Mechanical Engineering, both from Nigeria. His doctoral research is conducted at the Smart Multifunctional Materials Systems Laboratory under the supervision of Prof. Caterina Lamuta. His work focuses on the development, multiscale characterization, and engineering applications of novel artificial muscles.