Open-Water Tests of Two Ducted Propellers with and without Roughness on the Leading Edge of the Duct.

摘要

The report is an experimental continuation of two preceding reports where ducted propellers were designed for several alternative duct configurations at different advance numbers. Stock propellers were tested in two new type ducts and also in 19A ducts for comparison purposes. A modification of 19A, designated by 19A-MO1, has a somewhat better open-water efficiency at higher advance numbers than the 19A duct. Contrary to the preceding calculations, and to open-water tests performed elsewhere, the RGD3-00 duct has slightly inferior performance to the 19A duct. Because available stock propellers were used in the tests, the present experiments cannot be used as a verification of the design method. The main physical features obtained in the theoretical calculations appeared also in the tests. Turbulence on the ducts was stimulated by quartz beads of the size range of 0.1...0.6 mm. The length of the roughness region was 10 mm on both the inner and outer surfaces of the duct preceded by a width of 10 mm without the beads. The parasitic drag of the roughness decreased the open-water performance for most of the advance number range.