Azimuthal anisotropies such as the elliptic flow v2 are important tools for the study of the quark-gluon plasma (QGP) properties. Recent studies with transport models have suggested that most parton v2 comes from the anisotropic escape of partons, not from the hydrodynamic flow, even for semi-central Au+Au collisions at sNN=200 GeV. In this talk I will first introduce a multi-phase transport (AMPT) model and summarize our earlier findings on the parton escape mechanism. Then I will present our recent results on the flavor dependence in heavy ion as well as small system collisions at RHIC and LHC energies. In contrast to naive expectations, we find the charm v2 to be much more sensitive to the hydrodynamic flow than lighter quark’s v2, indicating that heavy quark flows are better probes of the QGP properties than light quark flow.