A new simulation model for damage of cavitation and silt erosion.

Wenjuan Gou, Ji-Jian Lian, Jian-hua Wu

Thursday 2 july 2015

14:35 - 14:50h at South America (level 0)

Themes: (T) Water engineering, (ST) Hydraulic machinery and industrial flows

Parallel session: 12C. Engineering - Industrial

Damage of cavitation and silt erosion usually occur simultaneously in a silt-laden river. For a hydropower project with high dam, hydraulic structures and hydro-machinery have been subjected to this damage. A large number of models for simulation of damage have been built for several decades, but most of them separately simulated cavitation and abrasion. A new model is necessary to be proposed for prediction of this synergetic damage. A model derived from experiments of cavitation and silt erosion for ASMT 1045 carbon steel in silt-laden water by means of a special vibratory apparatus. Three concentrations of sediment were tested (25 kg/m3, 50 kg/m3, and 85 kg/m3) for five mean sizes (0.531 mm, 0.253 mm, 0.063 mm, 0.042 mm and 0.026 mm) with 4 hours duration time. The results present that sediments aggravated cavitation damage if their sizes were larger than a critical size; conversely, the damage was relieved. Hence, sediment size strongly dominates the various effects on damage and this model was built on the basis of the phenomenon. The model was thus proposed with three steps. (1) A relation between characteristics of single size sediments and damage was confirmed, which embodies the effect of single size sediments on cavitation; (2) quantification functions were defined for the interaction effects of mixed-size sediments on cavitation damage; and (3) the model was obtained by an integral with accessible superimposition between the relation and the functions as the integrand and the grading curve as domain of integration. Comparison of the simulation data with experimental data indicated that the model is significant and probably used in a predictive way to study practical problems in silt-laden river.