The flow near the cavity detachment region of stable attached cavitation
was
examined using qualitative and quantitative flow visualization. The non-cavitating
and
cavitating flows around a hydrophilic brass and hydrophobic Teflon sphere
and cylinder
were examined. The location of non-cavitating boundary layer separation
and
cavity detachment was related to the free-stream Reynolds and cavitation
numbers.
The shape of the cavity near the detachment was greatly affected by the
material
of the cavitating object. The cavity interface on the hydrophilic test
objects curved
downstream to form a forward facing step. A region of recirculating fluid
existed
upstream of the cavity interface. The cavity detachment on the hydrophobic
test
objects was much closer to the location of boundary layer separation. The
forward
facing step and the recirculating region were nearly absent.
The measured flow field near the surface of the brass sphere, cylinder,
and hydrofoils
under cavitating and non-cavitating conditions was used to calculate the
position
of two-dimensional laminar boundary layer separation.
Thwaites' and Stratford's
methods were used to predict the location of boundary layer separation
upstream of
the cavity detachment. The predictions compared well with the observed
position of
separation.