The paper presents large eddy simulation (LES) study of a lifted hydrogen/nitrogen flame issuing from a pipe into a hot co-flowing gas stream. The basic configuration closely corresponds to the so-called Cabra flame, which we modified by: (i) mounting plates with circular and hexagonal orifices upstream of the exit section of the pipe; (ii) by adding flapping forcing at the nozzle exit. The role of the orifices and excitation is to intensify the mixing of large and small turbulent scales and to influence on the flame position and shape downstream of the nozzle exit. The combustion process is modelled using Conditional Moment Closure (CMC) model which is well suited for modelling of strongly unsteady flames. It was found that the magnitude of turbulent fluctuations in a direct vicinity of the orifices changes up to three times depending on the orifice shape and location. This translates in large differences in the flame dynamics. It was observed that excitation visibly alters the flame position and its shape.