AN INVESTIGATION OF A DIGITAL COMPUTER METHOD OF DETERMINING THE OPTIMUM DESIGN PARAMETERS OF SHROUDED PROPELLERS
GEORGIA INST OF TECH ATLANTA ENGINEERING EXPERIMENT STATION
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A digital computer method of determining the optimum design parameters of lightly loaded shrouded propellers is presented. For such a case the geometry of the vortex wake may be ideally described as a helical sheet of equalpitch vortex filaments arising from each blade trailing edge and a right circular boundary sheet composed of equal-pitch helical filaments arisingAT THE SHROUD TRAILING EDGE. The optimum condition for light loading requires that this wake vortex pattern move as a rigid body. This pattern of distributed vorticity is arbitrarily replaced with a finite number of finite, but unknown strength, vortex filaments. Using the Biot-Savart relation, an expression for the velocity components associated with each filament is obtained. Applying the boundary conditions to these sets of equations results in a set of simultaneous equations in terms of the unknown filament strengths. The blade bound vortex distribution obtained from the simultaneous solution is compared with the measurements previously obtained from potential tank models of a two- and four- bladed shrouded propeller. It is concluded that this digital computer method yields results that are adequate for design purposes, and it is recommended that this method be used instead of the potential tank method for obtaining the necessary charts and tables covering the range of design parameters for shrouded propellers.
- Marine Engineering