CAVITATION EROSION AND UNSTEADINESS
Abstract
This project, conducted in close cooperation with Prof. S. Ceccio and Prof. E. Johnsen(University of Michigan), will investigate the relationship between cavitation erosion andunsteadiness. It is motivated by a few publications indicating that cavitation aggressivenessmight be significantly enhanced by global flow unsteadiness. In order to further investigatethis hypothesis, we propose to carry out tests in the hydrodynamic tunnel of the LEGIlaboratory on a hydrofoil undergoing a transient pitching motion. Three differentexperimental techniques will be used. In a first step, visualizations will be made in order toidentify a number of unsteady cases for which the cloud, shed by the leading edge cavity,undergoes a quite violent collapse potentially associated to a highly erosive cavitating flow.These identified cases will be further investigated by impact load measurements usingpolyvinylidene fluoride (PVDF) pressure sensors flush mounted on the hydrofoil surface. Flowaggressiveness will be characterized by impact load histograms and the effect of unsteadinesson flow aggressiveness will be analyzed. In addition, an attempt will be made to carry outpitting tests in the most aggressive situations. It could be conjectured that, in spite of therelatively small free-stream velocity, the increase in flow aggressiveness due to unsteadinesswill cause some pitting. For the best chance of success, particularly soft materials will be usedsuch as annealed Aluminum. The project will conclude on the effect of unsteadiness on theerosive potential of the cavitating flow around a pitching hydrofoil. It will also provideconclusions on a number of related issues such as the use of PVDF sensor arrays for estimatingcavitation aggressiveness, the consistency of impact load measurements and pitting tests forassessing cavitation aggressiveness, the self-similarity of impact load histograms as well as pithistograms, the relevance of flow visualizations for assessing cavitation aggressiveness, andscaling laws followed by cavitation aggressiveness, all under unsteady conditions.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Nov 26, 2019
- Source ID
- N629091912146
Entities
People
- Henda Djeridi
Organizations
- National Center for Scientific Research
- Office of Naval Research
- United States Navy