  We investigate the triggering of star formation and the formation of stellar
clusters in molecular clouds that form as the ISM passes through spiral shocks.
The spiral shock compresses gas into $\sim$100 pc long main star formation
ridge, where clusters forming every 5-10 pc along the merger ridge. We use a
gravitational potential based cluster finding algorithm, which extracts
individual clusters, calculates their physical properties and traces cluster
evolution over multiple time steps. Final cluster masses at the end of
simulation range between 1000 and 30000 M$_{\odot}$ with their characteristic
half-mass radii between 0.1 pc and 2 pc. These clusters form by gathering
material from 10-20 pc size scales. Clusters also show a mass - specific
angular momentum relation, where more massive clusters have larger specific
angular momentum due to the larger size scales, and hence angular momentum from
which they gather their mass. The evolution shows that more massive clusters
experiences hierarchical merging process, which increases stellar age spreads
up to 2-3 Myr. Less massive clusters appear to grow by gathering nearby
recently formed sinks, while more massive clusters with their large global
gravitational potentials are increasing their mass growth from gas accretion.
