TRANSACTIONS OF THE KRYLOV STATE RESEARCH CENTRE

Science journal

 
ISSN (print) 2542-2324 /(online) 2618-8244


Articles of The Transactions of KSRC








Prediction of cavity volumes on rotating blades and scale effects



Full text article ( in russian)

Year

 
2021

Issue

 
397

Volume

 
3

Pages

 
13-24

Caption

 
Prediction of cavity volumes on rotating blades and scale effects

Authors

 
Amromin E.

Keywords

 
кавитация, лопасти, след, пограничный слой, поверхностное натяжение, масштабные эффекты

DOI

 
10.24937/2542-2324-2021-3-396-13-24

Summary

 
Object and purpose of research. Pressure pulsations induced by cavitating blades substantially contribute to flowinduced loads and amplify structural vibration. These pulsations depend on oscillation of the volume of cavities over blades. Prediction of them usually involves model tests and there are three kinds of scale effects influencing the cavity volumes. The first one is associated with the non-uniform inflows. The second one is associated with the combined influence of the blade boundary layer and surface tension on the cavity surface. The third one is associated with the cavity buoyancy.
Subject matter and methods.Because of complexity of blade flows, a qualitative analysis of similar unsteady non-uniform flows around 3D hydrofoils is useful. This paper presents such an analysis for a hydrofoil with the sections copied from a marine propeller blade. The inflows correspond to the wakes of a ship and of her model. Computations carried out using an analysis of viscous-inviscid interaction.
Main results. The qualitative explanation of observed trends and scale effects is obtained due to this analysis. In particular, the role of pressure side cavitation in full scale conditions is pointed out.
Conclusion. The difference of model and ship wakes results in the substantial difference in blade section angles of attack at the same blade loading. Therefore, in model tests the suction side cavitation is more extensive, whereas the pressure side cavitation may not appear, though it exists on full-scale ship propeller blade. This substantial scale effect has been usually out of previous considerations.

Rubrics

 
Naval architecture

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ISSN (print) 2542-2324 / ISSN (online) 2618-8244

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