Jr. Blake et al., COLLAPSING CAVITIES, TOROIDAL BUBBLES AND JET IMPACT, Philosophical transactions-Royal Society of London. Physical sciences and engineering, 355(1724), 1997, pp. 537-550
The present study is aimed at clarifying some of the factors which aff
ect the formation and direction of a liquid jet in a collapsing cavity
and the pressures induced on a nearby rigid boundary. The flow can be
accurately represented by a velocity potential leading to the use of
boundary integral methods to compute bubble collapse. For configuratio
ns with axial symmetry, the jet motion and that of the bubble centroid
are along the axis of symmetry. Examples are presented for bubbles cl
ose to a rigid surface and to a free surface. These are followed throu
gh to the toroidal stage after jet penetration. When there is no axis
of symmetry, fully three-dimensional computations show that the buoyan
cy force can cause the jet to move parallel to a vertical rigid bounda
ry, thus negating its damaging effect. The computational study is exte
nded to model cavitation bubble growth and collapse phases in a forwar
d;stagnation point flow as a model of reattachment of a boundary layer
a region where severe cavitation damage is often observed. The Kelvin
impulse is introduced to aid a better understanding of the mechanics
of bubble migration and jet direction in the examples presented. Final
ly a comparison between the spherical and axisymmetric theories is mad
e for an oscillating bubble in a periodic pressure field; this being o
f particular interest to current studies in acoustic cavitation and so
noluminescence.