Abstract
This paper describes the discharge coefficient C d and the critical cavitation number σcr in sea water through sharp-edged, bevel-edged and round-edged long orifices.
The ranges of test conditions are 0.39-0.59 MPa for the upstream pressure, 295-355 K for the upstream temperature and 7.7-28.5 m/s for the mean velocity, so that the cavitation number σ=0.11-10.99 and the Reynolds number Re = (2.1-15.4) ×104. Further, the cavitation characteristics of sea water are compared with those of fresh water. And the results are summarized as follows:
(1) Cd and σcr in sea water for sharp-edged long orifices agree well with those in fresh water. That is, the difference between sea water and fresh water has little effect on the cavitation characteristics. The same can be said about the effect of sea water temperature on the cavitation characteristics.
(2) As for sharp-edged long orifices, the ratio of orifice length to orifice diameter has an effect on Cd. But the effect in the supercavitating region of σ<σcr is different from that in the subcavitating and transient regions of σ>σcr. This is because the separated supercavitating cavity exists in the supercavitating region, and it does not exist in the subcavitating and transient region.
(3) The tendency of Cd and σcr for bevel-edged long orifice agrees qualitatively with those for sharp-edged one.
