Mewis Duct

The Mewis Duct is a pre-swirl wake-equalizing duct mounted ahead of the propeller, developed by Friedrich Mewis at Becker Marine Systems, that straightens and accelerates inflow while imparting a counter-swirl the propeller recovers. It typically saves 5 to 8 percent of propulsion power on slow, full-form bulk carriers and tankers and is one of the most widely retrofitted energy-saving devices, with several thousand units installed. The saving improves attained EEDI or EEXI and supports the CII rating.