Numerical Simulation On Scale Effect Of The Propeller-Rudder Interaction

Scale effects exist widely in the research of ship and ocean engineering.The scale effect in the interaction between the propeller and rudder will lead a deviation to the results and reduce the reliability of the results.Therefore,it is necessary to investigate the scale effect in the propeller-rudder interaction.Present paper studies the scale effect in the propeller-rudder interaction.The hydrodynamic performance,flow field pressure distribution,and rudder surface pulsation pressure in the propeller-rudder interaction under different scales and similarity principles have been investigated by a numerical method.Present study aimed to obtain the relationship between hydrodynamic performance coefficients,rudder surface pulsation pressure and scale under different similarity principles utilized several researches carried on open water propeller and propeller-rudder interaction under different similarity principles.First,based on a sufficient convergence analysis,the hydrodynamic performance of the single-blade INSEAN E779A propeller,the parameters of the flow field,and the cross section of the propeller tip vortex were studied under different similarity principles.The results show that when the Reynolds-Similarity not satisfied,the propeller thrust coefficient and efficiency will increase with when scale increase.The relative size of the propeller tip vortex cross section increases first and decrease afterwards with the increase of the scale no matter the Reynolds-Similarity satisfied or not.The relationship between the propeller tail vortex and flow field pressure distribution and scale of the propeller is identical with different similarity principles.The interaction between the single-blade INSEAN E779A propeller and NACA0020 rudder under different scales and similarity principles is analyzed.The analysis is also carried out based on a convergence analysis.Results under different scales and similarity principles are compared with the original results.The simulation was carried out under three conditions:the Reynolds-Similarity is not satisfied,the Reynolds-Similarity is satisfied,and the Fourier-Similarity is satisfied.Results show that as the scale increases,the propeller thrust coefficient increased but torque coefficient and rudder resistance coefficient decreased when Reynolds-Similarity is not satisfied.However,the pressure distribution of the flow field at the leading edge of the rudder and the pressure distribution at the side of the rudder appear to be very close under different scales and similarity principles.But the effect of the scale on the hydrodynamics performance become tiny when the Reynolds number approach critical Reynolds number.The time average value and frequency domain characteristics of rudder surface pulsating pressure caused by propeller tip vortices under different scales and similar conditions was investigated,and the dislocated of the tip vortex at different scales was analyzed using the frequency domain characteristics of pulsating pressure on rudder surface.It can be seen that the pressure on the surface of the rudder located in the region of the tip vortex flow mainly fluctuates on the blade frequency,and this phenomenon is independent of the scale under different similarity principles.When the Reynolds-Similarity is not satisfied,the amplitude of the pulsating pressure fluctuation on the pressure surface where the tip vortex collides with the rudder will increase with the increase of the scale,but the misalignment of the tip vortex on the rudder exists at different scales and similar conditions.The dislocation appeared on the rudder is not distinctly under a tiny scale but this dislocation in different scales is close when the Reynolds number beyond critical Reynolds number.The hydrodynamic coefficients of propellers and rudders,flow field pressure,the relationship between vortex-induced pulsation pressure,dislocation of tip vortex and the scale were analyzed under different similarity conditions,and it is of great significance to study the effects of scale and propeller-rudder interaction.