Abstract
For model tests on cavitation inception, the knowledge of the size distribution and frequency of occurrence of free nuclei is important. For this reason, an optical measuring method was developed for determining the bubble nuclei spectrum. In conjunction with measuring the bubble nuclei spectrum, a set of tests on cavitation inception was carried through, with each test leading basically to the same conclusions: The number and size of the bubble nuclei in water are dependent on the history of the particular water and on its content of contamination particles; the cavitation inception at a submerged body is strongly affected by the bubble nuclei content.