Critical review of propeller performance scaling methods, based on model experiments and numerical calculations

Jan A. Szantyr,Heinrich Streckwall,Tomasz Bugalski

doi:10.2478/pomr-2013-0043

Abstract

ABSTRACT The article presents the results of experimental and numerical investigation of propeller scale effects, undertaken in co-operation of the Hamburg Ship Model Basin (HSVA), Germany, and Ship Design and Research Centre (CTO SA), Poland. The objective of the investigation was to test the adequacy of the methods currently used to account for the propeller scale effect and to develop possible improvement of the methods. HSVA has conducted model experiments in the large cavitation tunnel together with panel method and CFD calculations. CTO SA has performed model experiments in the towing tank, together with lifting surface and CFD calculations. Both institutions have suggested different new approaches to the problem and different new procedures to account for the propeller scale effects. In the article the procedures are presented together with the description of the underlying experimental and theoretical research.

Highlights

Despite a rapid development of the computational fluid dynamics (CFD) the open water model experiments remain the basic source of information about the hydrodynamic characteristics of ship propellers
As the complete hydrodynamic similarity between model experiments and full scale operation of propellers cannot be achieved, the appropriate methods for correction of the so called scale effect had to be developed and implemented in order to convert the hydrodynamic characteristics of a propeller model into their full scale equivalent
The differences between the model and full scale propeller characteristics arise mainly due to a marked difference in model and full scale Reynolds numbers, they are connected to viscous flow effects in both scales

Summary

INTRODUCTION

Despite a rapid development of the computational fluid dynamics (CFD) the open water model experiments remain the basic source of information about the hydrodynamic characteristics of ship propellers. For an experimental based access to the inviscid propeller it is considered reasonable to reduce mixture effect from simultaneous appearance of laminar and turbulent flow as far as possible In the experiments it was aimed at the largest Reynolds numbers achievable with existing propeller hardware and test facilities. For the ITTC’78 method this is obvious from Fig. 4, where for propeller 2004 the full scale η was predicted slightly below model scale efficiency (using the standard roughness setting) This finding rather supports the necessity of a detailed treatment of viscous effect in the range of full scale Reynolds numbers (which was not addressed in the Lerbs/Meyne-method). The results of computations for the propeller CP312 are shown in Fig. 16 and 17 in the form of scale effect corrections related to the model scale values of respective parameters at the lowest Reynolds number, i.e. at 13 rps. - the alternative formula for blade section drag, used in Variants 3 and 4, seems to predict scale effect corrections for torque much better than the original ITTC78 formula

GENERAL CONCLUSION

Findings

ITTC Performance Committee