| Summary: | Cavitation phenomenon is important in hydraulic turbomachineries. With the construction of pumping stations and hydro power stations on plateau, the influence of nuclei fraction on cavitation becomes important. As a simplified model, a twisted hydrofoil was used in this study to understand the cavitation behaviors on pump impeller blade and turbine runner blade at different altitude levels. The altitudes of 0 m, 1000 m, 2000 m, 3000 m and 4000 m were comparatively studied for simulating the plateau situation. Results show that the cavitation volume proportion <i>f<sub>cav</sub></i> increases with the decreasing of cavitation coefficient <i>C<sub>σ</sub></i>. At a specific <i>C<sub>σ</sub></i>, high altitude and few nuclei will cause smaller size of cavitation. The smaller <i>C<sub>σ</sub></i> is, the higher the sensitivity Δ<i>f<sub>cav</sub></i> is. The larger <i>C<sub>σ</sub></i> is, the higher the relative sensitivity Δ<i>f<sub>cav</sub><sup>*</sup></i> is. On the twisted foil, flow incidence angle increases from the sidewall to mid-span with the decreasing of the local minimum pressure. When <i>C<sub>σ</sub></i> is continually decreasing, the size of cavitation extends in spanwise, streamwise and thickness directions. The cavity is broken by the backward-jet flow when <i>C<sub>σ</sub></i> becomes small. A tail generates and the cavity becomes relatively unstable. This study will provide reference for evaluating the cavitation status of the water pumps and hydroturbines installed on a plateau with high altitude level.
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