Influence of Viscous Effects on Model/Full-Scale Cavitation Scaling

Pertinent experimental results and theoretical prediction techniques are summarized and evaluated in terms of the influence of viscous effects on cavitation inception and the extent to which the boundary-layer properties complicate the correlation of model and full-scale cavitation inception. Consideration is given both to bodies having natural transition and bodies having laminar flow separation. The present approach assumes that cavitation inception is controlled by the pressure fluctuations in the region of natural transition or laminar separation superimposed upon the static pressure. In general, these pressure fluctuations occur very close to the minimum potential-flow pressure for full-scale bodies but occur farther aft of the minimum pressure for corresponding models evaluated at a lower Reynolds number. Predictions are in good agreement with results from numerous experiments on cavitating bodies which have either natural transition or laminar separation. Numerical examples demonstrate the order of magnitude of viscous effects on model/full-scale cavitation-inception scaling for a typical propeller blade section. Areas for additional cavitation research to strengthen the present approach are recommended.