Off-Design Performance Characteristics of Supercavitating Hydrofoils in Cascade

Abstract

The performance characteristics of supercavitating flapped foils in cascade, (such as the lift coefficient, the drag-lift ratio, and the limiting inlet flow speed) are calculated, for various cascade arrangements and flap angles, as well as flap-chord ratios, e. The extreme case when e = 1.0 corresponds simply to adjusting the cascade angle, such as in the Kaplan-turbine runner. It is found that the poor supercavitating cascade performance characteristics at conditions other than the designed condition, that is, the off-design performance characteristics, are noticeably improved with the use of flapped foils. The characteristics of cascaded foils without flaps, especially where there are no adjustments in cascade angle, make their use impractical in the off-design condition.