Estimates of Water Turbine Noise Levels

This work seeks to understand water turbine noise generation and to make preliminary estimations of the noise levels. Any structure attached to a turbine upstream its blades will generate unsteady fluctuating loads on the blade's surface, which are proportional to the radiated acoustic pressure. The noise levels of a simplified turbine based on existing designs surpass the ambient noise levels if the ocean at low frequencies (<20 Hz) by approximately 50 dB ref 1μPa, and stay under the ambient noise levels at higher frequencies for a blade-passing frequency of 0.83 Hz and point of observation (100 m, 45°, 45°) from the hub. Streamlining the cross-section of the upstream structure as well as reducing its width decrease the noise levels by approximately 40 dB ref 1 μPa, at low frequencies and moderately increase them at higher frequencies. Increasing the structure-rotor distance decreases the noise levels with increasing frequencies (>30 Hz).