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Context: The brightness of FUors increases by several magnitudes within oneto several years. The currently favoured explanation for this brightness boostis that of dramatically rising accretion from the disc material around a youngstar. The mechanism leading to this accretion increase is a point of debate.Aims: Choosing the Orion Nebula Cluster as representative we simulate accretionbursts driven by encounters in dense stellar environments. We investigatewhether properties like rise and decay times, event frequency etc. speak forencounters as a possible cause for FUor phenomena. Method: We combine clustersimulations performed with the Nbody6++ code with particle simulations thatdescribe the effect of a fly-by on the disc around a young star to determinethe induced mass accretion. Results: The induced accretion rates, the overalltemporal accretion profile, decay time and possibly the binarity rate we obtainfor encounter-induced accretion agree very well with observations of FUors.However, the rise-time of one year observed in some FUors is difficult toachieve in our simulations unless the matter is stored somewhere close to thestar and then released after a certain mass limit is transgressed. The severestargument against the FUors phenomenon being caused by encounters is that mostFUors are found in environments of low stellar density. We extend thediscussion to eccentric binaries and gravitationally unstable discs and findthat both models have similar problems in achieving the necessary rise-times.Conclusions: We predict that in dense young clusters these outbursts shouldpredominantly happen close to the cluster center and with large mass ratiosbetween the involved stars.(abridged)

Encounter-driven accretion in young stellar clusters - A connection to FUors?