The Measurement and Analysis of Force for Biomimetics of Flexible Airfoil in Oscillating Motion
Date Issued
2010
Date
2010
Author(s)
Cheng, Chi-Min
Abstract
The longstanding evolution has ensured fish which developed the smart propulsion system. This thesis focuses on the force status of Bionic fish swimming in flapping tail motion. Simulating fish flapping tail motion with Naca0012 flexible airfoil undergo pe-riodic oscillating motion by controlling Single-Axis robot and servo motor at the tow tank. Experiments are performed at a fixed value of the heave amplitude and of the Reynolds number to investigate the effects of variations of the Strouhal number by a step of 0.05 and of the maximum pitch angle by a step of . The experimental result indicates that the higher oscillating frequency produces the higher thrust coefficient. Moreover, it is found that the oscillat-ing motion with a high pitch angle produces larger maximum transient peak thrust than a small pitch angle. However, keeping the greater thrust coefficient in the small pitch angle and high-speed towing that can efficiently reduce drag.
According to the literature review, flexible airfoil affects the thrust coefficient in-distinctly relative to rigid airfoil. Therefore, through force elements theory, we can carry out numerical simulations of rigid airfoil with same parameters to observe various force elements contributions. Comparisons between numerical and experimental results show that the trends of total lift and thrust under some conditions are similar. Here, we also decompose and quantify the force into four components: the contribution associated with the acceleration of the airfoil; the contribution by the velocity of the airfoil; the contribution by the surface vorticity and friction on the airfoil; the contribution of pres-sure force due to vorticity within the flow field. This theory identify the main sources of the propulsion system and proportion of the components in the different parameters. The results indicate that acceleration term and vorticity of the flow field term play a rule key in high thrust production in a full flapping.
Subjects
Bio-inspired propulsion
Oscillating motion
Force elements theory
Type
thesis
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