The Effects of Non-Uniformity and Turbulence of Flow on Hydrodynamic Characteristics of Propeller

Abstract

It is recently noticed that the non-uniformity of flow brings some deviation of the relative rotative efficiency from the unit and the difference of the effective wake factor from nominal one. The investigations are expected to enter in more details either experimentally or theoretically. The present paper is the report of the experiments and analysis works about the hydrodynamic characteristics of the model propeller acting in the wake flow of the alternate mesh screens of different patterns, such as some circumferential non-uniform wakes of the cos nθ function mode, a radial non-uniform wake and homogeneous wakes.The measurements of velocity fields of cos nθ mode have shown the well correlation of the intensity of turbulence with the shear rate of the velocity profile along the circumference. From the results of the performance tests of the propeller behind the one or two uniform meshes screen, it has been found that the influence of turbulence of flow reduces the low Reynolds number effect of the model propeller. Accordingly, the characteristics of the model propeller in the wake of the two uniform meshes screen has been offered to apply to the analysis of the self-propulsion factor at any low Reynolds no.It has been shown that the circumferential non-uniformity of the cos nθ mode, where n≤6, raises the efficiency of the propeller higher than that of the open condition, that is the high relative rotative efficiency over the unit. The results of analysis of data based on some theoretical considerations have allowed us to conclude that the relative rotative efficiency responds to the circumferential non-uniformity of flow nonlinearly and quasi-stationarily.