Biology-Inspired Propulsion

"Mature, efficient propellers still produce noise that can reduce the stealth of the Navy's unmanned underwater vehicles (UUV) and compromise sensitive missions. In the interests of national security, it is essential that UUVs operate as quietly aspossible. We propose to increase UUV stealth with a practical biomimetic device, the Oscillation OverThruster, that substantially reduces a propeller's radiated noise by decreasing propeller RPM (w) while maintaining the same thrust output (t). This ismade possible because a portion of the radiated noise of a spinning propeller is proportional to w6. Our device is mechanically simple and is based on analyses of an unsteady phenomenon that has been shown to increase lift on animal wings to 150% of thevalues expected for the steady state used by propellers. We propose a three-step, cost-efficient effort aimed at quickly transforming this natural phenomenon into Navy-usable technology-specifically, a retrofit Oscillation OverThruster silencing unit (O2)for Naval UUVs. OverThruster-enhanced propeller systems promise more stealth, greater speed, and extended range, all of which are critical success factors in UUV missions. In addition to tactical applications, the Oscillation OverThruster should findwidespread use in civilian applications."