8 research outputs found
A new reduced network to simulate detonations in superbursts from mixed H/He accretors
We construct a new reduced nuclear reaction network able to reproduce the
energy production due to the photo-disintegration of heavy elements such as Ru,
which are believed to occur during superbursts in mixed H/He accreting systems.
We use this network to simulate a detonation propagation, inside a mixture of
C/Ru. As our reference, we use a full nuclear reaction network, including 14758
reactions on 1381 nuclides. Until the reduced and full networks converge to a
good level of accuracy in the energy production rate, we iterate between the
hydrodynamical simulation, with a given reduced network, and the readjustment
of a new reduced network, on the basis of previously derived hydrodynamical
profiles. We obtain the thermodynamic state of the material after the passage
of the detonation, and the final products of the combustion. Interestingly, we
find that all reaction lengths can be resolved in the same simulation. This
will enable C/Ru detonations to be more easily studied in future
multi-dimensional simulations, than pure carbon ones. We underline the
dependence of the combustion products on the initial mass fraction of Ru. In
some cases, a large fraction of heavy nuclei, such as Mo, remains after the
passage of the detonation front. In other cases, the ashes are principally
composed of iron group elements.Comment: 6 pages, 12 figure
Effect of Initial Disturbance on The Detonation Front Structure of a Narrow Duct
The effect of an initial disturbance on the detonation front structure in a
narrow duct is studied by three-dimensional numerical simulation. The numerical
method used includes a high resolution fifth-order weighted essentially
non-oscillatory scheme for spatial discretization, coupled with a third order
total variation diminishing Runge-Kutta time stepping method. Two types of
disturbances are used for the initial perturbation. One is a random disturbance
which is imposed on the whole area of the detonation front, and the other is a
symmetrical disturbance imposed within a band along the diagonal direction on
the front. The results show that the two types of disturbances lead to
different processes. For the random disturbance, the detonation front evolves
into a stable spinning detonation. For the symmetrical diagonal disturbance,
the detonation front displays a diagonal pattern at an early stage, but this
pattern is unstable. It breaks down after a short while and it finally evolves
into a spinning detonation. The spinning detonation structure ultimately formed
due to the two types of disturbances is the same. This means that spinning
detonation is the most stable mode for the simulated narrow duct. Therefore, in
a narrow duct, triggering a spinning detonation can be an effective way to
produce a stable detonation as well as to speed up the deflagration to
detonation transition process.Comment: 30 pages and 11 figure