Transient flow and noise characteristics of accelerated flow past a hydrofoil with whale-like wavy leading edge

As the concept of sustainable development gains traction, the adoption of environmentally friendly energy conversion technologies becomes increasingly prevalent in daily life, particularly in the development and application of fluid machinery for ocean current and tidal energy. However, the use of fluid machinery often involves transient processes, and while existing research has investigated the flow and noise characteristics of devices like hydrofoils, most studies focus on steady-state performance analysis, with less attention given to transient conditions. The field of bio-inspired noise reduction in hydrodynamics, especially under such circumstances, remains relatively underexplored. In response to this, we propose a novel bio-inspired hydrofoil based on the NACA0015 (National Advisory Committee for Aeronautics), employing large eddy simulation for detailed numerical simulations of both the prototype and the bio-inspired design. The simulations were conducted with a Reynolds number of 8000, an attack angle of 30°, and an initial velocity gradually accelerated to 0.1 m/s over a 1 s period with a constant acceleration of 0.1 m/s2. Following this, we employed the Ffowcs Williams–Hawkings analogy to analyze the acoustic characteristics of the hydrofoil in both near and far fields. Through simulation and analysis, we observed that during acceleration, the unique structure of the bio-inspired hydrofoil modifies the pressure distribution on the suction surface, causing turbulence at the leading edge to break into smaller vortices. This leads to a reduction in low-frequency noise production. By combining the pressure distribution, vortex patterns, turbulent kinetic energy, and near- and far-field noise, we conclude that the proposed biomimetic hydrofoil can reduce the noise up to 3.3 dB at low Reynolds number and up to 10.68 dB at high Reynolds number. This study, by integrating bio-inspired design with in-depth analysis of transient flow characteristics, offers valuable insights for noise reduction technologies in fluid machinery under complex transient conditions.