Image Analysis of Fine Structures of Supercavitation in the Symmetric Wake of a Cylinder

The fine structure of supercavitation in the wake of a symmetrical cylinder is studied with high-speed video cameras. The flow is observed in a cavitation tunnel at the speed of 8m/sec when the sidewall and the wake are partially filled with the massive cavitation bubbles. The present experiment observed that a two-dimensional ripple wave with a wave length of 0.3mm is propagated in a downstream direction, and then abruptly increases to a thicker three-dimensional layer. IR-photography recorded that the wakes originated from the horseshoe vortexes alongside the cylinder. The wake was developed to inside the dead water zone, which absorbed the bubbly wake propelled from the separated vortices at the center of the cylinder. A remote sensing classification technique (maximum most likelihood) determined that the surface porosity was 0.2, and the mean speed in the mixed wake was 7m/sec. To confirm the existence of two-dimensional wave motions in the interface, the experiments were conducted at a very low frequency, and showed similar gravity waves in both the upper and lower interfaces.

Authors:

• Y. Obikane
• M.Kaneko
• K.Kakioka
• K.Ogura

Keywords:

• Supercavitation
• density gradient correlation

References:

[1] Y.Obikane, "Research on the Correlation of the fluctuating Density
Correlation of the compressible Flows", Journal of Energy and Power
Engineering, Volume4, Number7, July 2010(Serial Number 32), pp27-31.
[2] O.Furuya,A.J.Acosta, "A note on the calculation of Super-Cavitation
Hydrofoils with Rounded Noses", Journal of Fluid Engineeering 1973
June pp221-228
[3] Jean-Baptishe Leroux Olivier Coutier-Delgosha Jacques Andre Astolfi,"
A joint experimental and numerical study of mechanisms associated to
instability of partial cavitation on two-dimensional Hydrofoil", Fifth
International Symposium on Cavitation (CAV2003) Osaka, Japan,
November 1-4,2003