Numerical analysis and experimental investigation of combined erosion of cavitation and sandy water erosion

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Based on the computational fluid dynamics method, simulating the actual working conditions of turbines, the internal vapor–liquid–solid flow fields (total pressure and volume fraction of vapor phase) on the test turntable surface with cavitation source holes are numerically calculated under the combined erosion of cavitation and sandy water erosion. The vapor–liquid–solid combined erosions of different materials (Q235, 45#, 40Cr, and HT200) are tested on the reconstructive rotary wear test rig. The scanning electron microscopic photos and three-dimensional morphologies of different material specimens are displayed and analyzed. The numerical results show that the high pressure on the specimen surface is mainly distributed near the cavitation hole along the direction of the water flow (counterclockwise), and it outspreads at a certain angle from the both side of the cavitation hole, and the high pressure distribution looks like fishtail shape. The vapor phase mainly exists in the vicinity of the cavitation hole, and it looks like a big long comet tail and spreads along the direction of the water flow. The combined erosion region is mainly near the cavitation hole and here there are the vapor phase and large pressure gradient, and the combined erosion is more severe than the single cavitation erosion or single sandy water erosion. The experimental results show that in the regions of much vapor phase and a little pressure gradient, the main failure mode of the plastic materials (Q235 and 45#) is sandy water erosion, and the main failure mode of the plastic material of larger hardness (40Cr) and the brittle material (HT200) is cavitation erosion. The experimental results basically coincide with the calculated results. The scanning electron microscopic photos and three-dimensional morphologies of different material specimens are consistent with the macro-erosion photos.