Star clusters are composed of a large number of stars bounded by their self-gravity. Different kind of clusters, such as open clusters, globular clusters (GCs), young massive clusters (YMCs), nuclear clusters, are classified according to their mass, age, central density, concentration and their environments, etc. Star clusters are usually considered ideal systems to study stellar evolution since stars in clusters have been assumed to be coeval and share the same chemical properties. Thanks to the recent development of computational resources, it is now able to simulate realistic systems to understand the dynamical history behind observed star clusters. In this talk, I will present recent works that I have done here in KIAA. I will mainly cover two topics. One is the interpretation of multiple populations, which is recently found in some YMCs in the Magellanic Clouds. I tested two possible scenarios (ad hoc formation and merger scenarios) numerically to check how either scenario is likely. I will also discuss how two different scenarios produce different kinematic fingerprints. The other topic is binary black holes (BBH) from GCs as gravitational wave sources. Especially I will focus on the correlation between the production of gravitational wave BBHs and their host GCs' properties like mass, size, binary fractions. I will provide analytic expressions for the dependence of the number of BBH mergers from individual GCs on the main cluster’s structural properties and the time evolution of the merger rates of these BBHs. These expressions provide an essential ingredient for a general framework allowing to estimate the merger rate density.
