Cavitation inception in a turbulent shear flow
Experimental investigations were made into the inception processes in a large turbulent free shear layer generated by a sharp edged plate in a water tunnel at Reynolds numbers up to 2 /times/ 10/sup 6/. Optical techniques were used to study the relation of cavitation inception to flow characteristics, in particular to the coherent vortices of the free shear layer turbulent structure. Two distinct types of vortex motion were evident, primary spanwise and secondary longitudinal vortices. Cavitation inception consistently occurs in the secondary shear layer vortices and more fully developed cavitation is visible in both structures, with the streamwise cavities typically confined to the braid regions between adjacent spanwise vortices. Measurements of fluctuating pressures in the turbulent shear layer were made by holographically monitoring the size of air bubbles injected into the non-cavitating flow, showing that pressure fluctuations were much stronger than previously reported, with positive and negative pressure peaks as high as 3 times the freestream dynamic pressure, sufficient to explain the occurrence of cavitation inception at high values of the inception index. The occurrence of inception in the secondary vortices of the shear layer, and previous reports of velocity dependence of these cores, may provide the key to explaining the commonly observed Reynolds number scaling of the inception index in shear flows. 20 refs., 9 figs., 1 tab.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (USA)
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 7128447
- Report Number(s):
- SAND-88-1110C; CONF-880716-5; ON: DE88011486
- Country of Publication:
- United States
- Language:
- English