Prediction of cavitation erosion: An energy approach

The objective is to define a prediction and transposition model for cavitat ion erosion. Experiments were conducted to determine the energy spectrum as sociated with a leading edge cavitation. Two fundamental parameters have be en measured on a symmetrical hydrofoil for a wide range of flow conditions: the volume of every transient vapor cavity and its respective rate of prod uction. The generation process of transient vapor cavities is ruled by a St rouhal-like law related to the cavity size. The analysis of the vapor volum e data demonstrated that vapor vortices can be assimilated to spherical cav ities. Results are valid for both the steady and unsteady cavitation behavi ors, this latter being peculiar besides due to the existence of distinct vo lumes produced at specific shedding rates. The fluid energy spectrum is for mulated and related to the flow parameters. Comparison with the material de formation energy spectrum shows a remarkable proportionality relationship d efined upon the collapse efficiency coefficient. The erosive power term for merly suggested as the ground component of the prediction model, is derived taking into account the damaging threshold energy of the material. Art ero sive efficiency coefficient is introduced on this basis that allows to quan tify the erosive potential of a cavitation situation for a given material. A formula for localization of erosion is proposed that completes the predic tion model. Finally, a procedure is described for geometrical scale and flo w velocity transpositions.