IMPROVING PROPULSION PERFORMANCE OF FLAPPING CAUDAL FIN MODEL USING VARIABLE STIFFNESS MECHANISM

• Main Author: Evan Harlan, Stefanus
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/75406
• Institution: Institut Teknologi Bandung

Fish are thought to be efficient swimmers due to their ability to control the stiffness of their body and fin by means of muscle activities under different swimming conditions. This leads to the needs of developing flapping propulsion system of bioinspired underwater vehicles, particularly by improving the performance of caudal fin as the main propulsor. The conducted research focuses on the experimental-based optimization of rectangular-shaped caudal fin using variable-stiffness mechanism to achieve high propulsion performance under various flapping conditions. The experimental approach involves direct force measurement and flow field analysis around the flapping fin using nonintrusive particle image velocimetry (PIV) measurement. The obtained data show that all kinematics and structural parameters are correlated and exhibit unique conditions during the optimum net-thrust generation. By employing the variable-stiffness fin, various optimum conditions can be achieved by properly adjusting the fin stiffness. In analyzing the flow behaviour, a pattern of counter-rotating vortex-pair generation is observed which induces a strong central jet flow responsible for the optimum net-thrust generation. Meanwhile, a generation and destruction pattern of counter-rotating vortex-pair appears behind the fin at the negative net-thrust condition, which induces a short period of central jet flow responsible for drag and lateral force generation.