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 include Fluid-structure interactions          Mechanical systems and structures         Computational nonlinear dynamics         Analytical techniques                  Bifurcation and dynamic instability         Rotating systems  Modal interactions and energy transfer Nonsmooth systems