Design and CFD Analysis of Biomimetic Turbine Blade for Low-velocity Tidal Streams

Abstract

A Horizontal Axis Tidal Turbine blade with an NREL S814 profile was designed and optimized for low-velocity tidal streams using QBlade. The optimized blade is then integrated with a biomimetic concept and modeled. This biomimetic concept took inspiration from the protuberances on the pectoral fins of Megaptera novaeangliae or Humpback Whale. Two biomimetic configurations, namely 0.15C and 0.2C, were incorporated to a baseline blade. These blades are then subjected to steady-state filtering to see which biomimetic configuration has the highest coefficient of lift and glide ratio at 0° to 20° angle of attack at an inlet velocity of 0.5m/s. The result showed that the 0.2C configuration has the highest $\mathrm{C}_{\mathrm{L}}$/$\mathrm{C}_{\mathrm{D}}$, which is 6.3109 at 10° angle of attack. 0.2C also produced a CL of 0.6115 at 19° before it stalled at 20°. 0.15C produced a $\mathrm{C}_{\mathrm{L}}$/$\mathrm{C}_{\mathrm{D}}$ of 6.1551 at 10° and CL of 0.5883 at 18° before it stalled at 19° while the baseline blade, 0.0C, stalled at 8° and produced a $\mathrm{C}_{\mathrm{L}}$/$\mathrm{C}_{\mathrm{D}}$ of 5.3008 and CL of 0.2402 at 7°. The 0.2C configuration was then integrated into a HATT setup and was then subjected to transient simulation at inlet velocities of 0.5, 0.64, and 1.136m/s and a specified Tip Speed Ratio of 6. The Biomimetic HATT produced a Torque of 174.914 Nm, 288.955 Nm, 918.054 Nm, Thrust of 1299.09 N, 2134.20 N, 6742.34 N, and Power of 262.371 W, 554.794 W, and 312S.72SW at 0.5, 0.64, and 1.136 m/s inlet velocities, respectively. The results showed that it has 37.46% lesser torque and 6.13% lesser power output at 0.64m/s. At 1.136m/s inlet velocity, it has a 36.93% lesser torque and 5.39% lesser power output when compared to a BEM modified blade designed at a TSR of 4. The biomimetic HATT performed better than the blade design of [3] and [4] since this biomimetic design has lesser torque and higher rotational velocity at (a) almost the same power output, (b) same inlet velocities, and (c) the same swept area. Furthermore, the high TSR operation reduces cost in the design of the power take-off system since it can employ direct drive mechanisms.