The empirically observed dependency of German KWU PWRs' neutron noise amplitudes in the range of 0-2 Hz on the mechanical type of fuel assemblies is currently actively researched and probably governed by fluid-structure interaction in the reactor core. In order to improve the state of knowledge about this range, an algorithm simulating the proposed mechanism of a coherent dynamical fuel assembly deflection changing the local reflector thickness and by this affecting the neutron flux on a larger scale was implemented in the reactor dynamics code DYN3D. The dynamical deflections are calculated prior to the DYN3D run and get translated to dynamical reflector thickness variations. The impact of the thickness variations on the group constants in DYN3D is quantified by respective coefficients obtained with the lattice code CASM05. The DYN3D simulation reproduces some important characteristics of the relevant noise phenomena and confirms that coherent fuel assembly deflection may play a crucial role in the KWU PWR neutron noise. It is pointed out that the actual mechanisms driving such deflection and transferring their action to the neutron detectors has to be matter of further investigation. Approaches for further research are given.