New Proposal for Calculating the Cavitation Criterion of Marine Screw Propellers

Abstract

Although the methods of setting up the limit of cavitation of marine propellers have been introduced by various authors, it seems that the most eligible method may be the one introduced by Mr.Y.Nakajima utilizing the Schoenherr's pressure drop diagram of aerofoils reduced from Gutsche's wind tunnel experiments. In this process, Mr.Nakajima ingeniously made out the lift coefficient ζ_a by geometrical calculation, but his method appears to be rather difficult for unskilled designers to understand and somewhat complicated in calculation. In this connection the author tried and succeeded in obtaining the value of ζ_a very simply from propeller thrust and applied it to estimate the cavitation criterion. By this new method it is suggested that we can rather easily find the most convenient camber ratio of blade section at 0.9 Rand furthermore it may be emphasized that it allows us the capability of immediately obtaining the cavitation characteristics of blade section at any position such as 0.7R or 0.8R.