Analyse de l'influence de rugosités organisées sur les écoulements cavitants instationnaires

Abstract : There are too many examples around us which prove that in hydrodynamics a polite surface does not present systematically the hydrodynamics advantages were expected on a rough surface. The roughness influence actively the development of the turbulent boundary layers and interact differently according to their physical characteristics. Plunged into a hydraulic flow to high number of Reynolds, blades of propellers activate locally a physical phenomenon, called cavitation, which corresponds to the appearance of bubbles of gas and vapor in a liquid submitted to a depression. Within the framework of this thesis, the experiments are led in a tunnel of cavitation, and measures by LDV were realized so as to define the profile of the speed vector of the flow in the longitudinal direction. A very high-speed camera CCD allows the taking of image on the formation of pockets and clouds of cavitation. In the case of the 2D hydrofoil, the experiments led on the various partially grooved patches highlighted the character hydrodynamics different on each of them, because the size of cavitants pockets differs according to the characteristics of the indentations. The results showed that the depth of the indentations is a determining parameter, while the smallest depths of grooves (smaller than the height of the viscous sublayer) have no effect on the length of cavitants pockets. Certain patches provoke variations on the instabilities of cavitation for which the length of cavitants pockets is reduced. The study of the frequency of detachment of cavitants pockets, by means of the fast camera allowed to highlight two regimes of different cavitation. This study demonstrated the feasibility of a passive control of the cavitation over a profile of venturi by modifying the state of surface by indentations organized in the direction of the flow.
Complete list of metadatas

Cited literature [47 references]  Display  Hide  Download

https://pastel.archives-ouvertes.fr/pastel-01062146
Contributor : Abes Star <>
Submitted on : Tuesday, September 9, 2014 - 11:42:09 AM
Last modification on : Wednesday, May 29, 2019 - 5:53:28 PM
Long-term archiving on : Wednesday, December 10, 2014 - 12:06:48 PM

File

MEHAL.pdf
Version validated by the jury (STAR)

Identifiers

  • HAL Id : pastel-01062146, version 1

Collections

Citation

Jean Elie Mehal. Analyse de l'influence de rugosités organisées sur les écoulements cavitants instationnaires. Mécanique [physics.med-ph]. Ecole nationale supérieure d'arts et métiers - ENSAM, 2014. Français. ⟨NNT : 2014ENAM0013⟩. ⟨pastel-01062146⟩

Share

Metrics

Record views

3750

Files downloads

10040