This first of three volumes includes papers from the second series of NODYCON, which was held virtually in February of 2021. The conference papers reflect a broad coverage of topics in nonlinear dynamics, ranging from traditional topics from established streams of research to  those from  relatively unexplored and emerging venues of research. These includeFluid-structure interactions         Mechanical systems and structures        Computational nonlinear dynamics        Analytical techniques                 Bifurcation and dynamic instability        Rotating systems Modal interactions and energy transferNonsmooth systems