Speaker
Marta Šlapanská
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.3005.pdf
Study of cavitation in liquid water under the action of inhomogeneous
pulsed electric fields: application to sub-nanosecond electrical breakdown
M. Šlapanská1 , M. Kubečka1 , A. Obrusník1 , J. Hnilica1 and Z. Bonaventura1
1 Department of Physical Electronics, Faculty of Science, Masaryk University, Brno, Czech
Republic
Sub-nanosecond electrical breakdown in dielectric liquids is of vital interest, e.g. for ap-
plications in high-voltage insulation and high-current switching. Liquid dielectrics in strong
nonuniform electric fields are under influence of electrostrictive force that tents to move the
fluid into the regions with higher electric field. If the voltage rise is fast enough, the liquid does
not have enough time to set into motion thanks to inertia. Then the poderomotive force induces
significant stress in the bulk of the liquid leading to generation of a negative pressure. At certain
threshold, the negative pressure causes cavitation ruptures of the fluid. Free electrons then can
be produced by emission from the surface inside the cavity and accelerated to energies exceed-
ing the energy for ionization of water and contribute thus to formation of microstreamers. In this
work we use hydrodynamic model for motion of dielectric fluid to study the dynamic of water
in a pulsed strongly inhomogeneous electric fields in the approximation of compressible flow
described by equation of continuity for mass and momentum [1, 2]
∂ρ
+ ∇ · (ρ~u) = 0
∂t
∂~u ~ 2 1
ρ + (~u · ∇)~u = −∇p + F + η ∇ ~u + ∇(∇ ·~u)
∂t 3
where ρ is the fluid density, p is the pressure, ~u is the velocity, η is the dynamic viscosity, and
~F ≈ ε0 ε∇E 2
is the force acting on the body of the fluid thanks to inhomogeneous electric field E. The set of
continuum equations is closed by the Tait equation of state for water [3, 4, 5].
The model allows to find pressure field in the liquid for considered electrode geometry and
high voltage pulse and calculate probability for cavitation voids generation.
This contribution is funded by the Czech Science Foundation grant no. 18-04676S.
References
[1] M. N. Shneider and M. Pekker, Phys. Rev. E 87, 043004 (2013)
[2] M. N. Shneider and M. Pekker, J. Appl. Phys. 114, 214906 (2013)
[3] R. I. Nigmatulin and R. Kh. Bolotnova, High Temperature 49 2, 303 (2011).
[4] R. I. Nigmatulin and R. Kh. Bolotnova, High Temperature 46 3, 325 (2011).
[5] Y.-H. Li, J. Geophys. Res. 70 10, 2665 (1967)
