Phenomenological models of cavitation erosion kinetics
Phenomenological models of cavitation erosion kinetics
Phenomenological models of cavitation erosion kinetics
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J.Steller, P.Kaczmarzyk: <strong>Phenomenological</strong> <strong>models</strong> <strong>of</strong> <strong>cavitation</strong> <strong>erosion</strong> progress. 74. NUMERICAL CODE TO CALCULATE PARAMETERSOF EROSION CURVESAND THE ANALYSIS OF OBTAINED RESULTSA computer code APROX [9] has been developed in the Borland Pascal language in orderto accomplish the necessary calculations. The code enables approximation <strong>of</strong> mass, volumeand mean depth <strong>of</strong> penetration curves following the <strong>models</strong> described in section 2, usingone <strong>of</strong> the above mentioned minimisation methods. The curves <strong>of</strong> instantaneous and cumulative<strong>erosion</strong> rate and basic single-number parameters are also determined. In case <strong>of</strong> severalspecimens the code determines also the averaged curves and parameters. A hard copy <strong>of</strong> thecomputer screen, taken during processing <strong>of</strong> the E04 data at the IMP PAN rotating disk canbe seen in Fig.4.Fig.4 A hard copy <strong>of</strong> the computer screen, taken during processing the E04 dataThe analysis conducted has proved very good convergence <strong>of</strong> all the methods in casethe process under consideration covers also the period <strong>of</strong> steady or quasi-steady damage rate(Fig.5a).The evident superiority <strong>of</strong> the simplex and Levenberg-Marquardt methods over that <strong>of</strong>Powell was stated already in the early stage <strong>of</strong> analysis. Currently, no problems occur whencalculating the <strong>erosion</strong> curves according to the <strong>models</strong> <strong>of</strong> K.Steller and L.Sitnik. Calculationby means <strong>of</strong> the simplex method does not always end in global minimisation <strong>of</strong> formula (11).