Distinctive Features of Using the Propulsor of the Underwater Sail Type and the Direct-Flow Wave Propulsor on a Semisubmerged Catamaran

We present the results of experimental investigations of the efficiency of the direct flow wave propulsor and the propulsor of the underwater sail type on the models of semisubmerged catamaran boat with a small area of the section along the waterline. The effects observable in the case of the propulsor of the underwater sail type are qualitatively the same as for the previously studied swinging wing, namely, the greatest efficiency is observable, when the propulsor is situated near the free surface, while its efficiency is rapidly reduced with propulsor immersion. The propulsor efficiency varies only slightly with ship hull immersion, whereas the working frequencies are considerably reduced as compared with those of floating structures. In this case, the working frequencies vary in proportion to the model boat scale. Comprehensive studies of the direct-flow wave propulsor efficiency were performed, an inclined flat plate being fixed at the hulls of a semisubmerged ship as a working element. The optimal parameters of the propulsor were noted, when it efficiently operates on the waves with the greatest steepness (storm waves). Experiments showed that the efficiency of the wave propulsors of the swinging wing or underwater sail types in their operation ranges is somewhat higher than that of the direct-flow propulsor. However, under the rough water conditions the direct-flow propulsor has its own advantages, since precisely in this case it demonstrates its greatest efficiency, while the other versions considered are efficacious in the wavelength range dependent on the ship length and, generally speaking, do not coincide with the storm wave length.