Hydrofoil vibration and noise reduction with leading edge isolation

Abstract

A technique for reducing the vibration and noise from hydrofoils subject to unsteady hydrodynamic loads was demonstrated experimentally. Unsteady loads are generated when hydrofoils interact with approach‐flow disturbances such as hull boundary layer turbulence or wakes from upstream rotors. Since the unsteady loads are known to be concentrated in the vicinity of the leading edge, a single stage vibration isolation mount was incorporated into a hydrofoil at its 20% chord location to inhibit the leading edge‐generated unsteady loads from being transmitted to the remainder of the foil and any structures coupled to it. The hydrofoil was tested in a water tunnel facility with a wake generator placed upstream to produce the approach‐flow disturbances. The reduction in the loading on the portion of the hydrofoil isolated from the leading edge was inferred from vibration measurements. Reductions of 5 to 10 dB were demonstrated.