  We have developed a simulation model of particle acceleration in coronal
shock waves. The model is based on a Monte Carlo method, where particles are
traced in prescribed large-scale electromagnetic fields utilizing the guiding
center approximation. The particles are scattered in the turbulence according
to quasilinear theory, with the scattering amplitude directly proportional to
the intensity of Alfv\'en waves at gyro-resonant wavenumbers. The Alfv\'en
waves are traced simultaneously with the particles, so that the wave field is
propagated outwards from the Sun using WKB propagation supplemented with a
phenomenological wavenumber diffusion term and a growth rate computed from the
net flux of the accelerated particles. We consider initial wave amplitudes
small enough to allow rapid escape of particles from the shock to the ambient
medium. Thus, in our model the Alfv\'en waves responsible for the diffusive
acceleration of particles are generated by the accelerated particles
themselves. In this work, we study the effects of non-constant shock velocity
and non-monotonic Alfv\'en velocity on particle acceleration scenarios. We
report in particular how the deceleration of a shock affects particle intensity
and turbulence power evolution in the vicinity of the shock.
