Despite the recent progress in experimental and computational techniques, the phenomenon of condensation in freely expanding flows is still poorly understood. In this paper, a computational method directly representing the physics of the coupled cluster formation - gas expansion processes, Molecular Dynamics (MD), is used to characterize clustering in a supersonic jet expansion. The obtained results favor the scenario in which the condensation starts from dimer formation in triple collisions of monomers. Since due to the inherent MD limitations the simulated system is very small, another computational technique, direct simulation Monte Carlo (DSMC) is proposed to simulate the condensation in real-size supersonic jets. Implementation of various types of interactions among monomers and clusters in DSMC is discussed and a way to effectively characterize them via separate MD calculations is proposed. In this way, the DSMC method keeps the accuracy of the MD method, while at the same time being capable of simulating practically important systems.