  In two-dimensional decaying homogeneous isotropic turbulence, kinetic energy
and enstrophy are respectively transferred to larger and smaller scales. In
such spatiotemporally complex dynamics, it is challenging to identify the
important flow structures that govern this behavior. We propose and numerically
employ two flow modification strategies that leverage the inviscid global
conservation of energy and enstrophy to design external forcing inputs which
change these quantities selectively and simultaneously, and drive the system
towards steady-state or other late-stage behavior. One strategy employs only
local flow-field information, while the other is global. We observe various
flow structures excited by these inputs and compare with recent literature.
Energy modification is characterized by excitation of smaller wavenumber
structures in the flow than enstrophy modification.
