| This thesis reports studies of dynamics and coherent structures in two-dimensional turbulence. Measurements of a quasi-two-dimensional laboratory flow were made using particle tracking velocimetry. Velocity fields were extracted and analyzed using a variety of computational tools, and results from the data analysis were interpreted to gain a better understanding of the relationship between the turbulent dynamics and the coherent structures.;The turbulent dynamics were primarily characterized using Filter Space Techniques (FSTs) that allow the calculation of spatially resolved scale-to-scale fluxes of both energy and enstrophy. The theoretical basis of FSTs is discussed, and it is shown that the energy and enstrophy fluxes can be decomposed into three logically distinct components that correspond to different types of wavevector triad interactions in spectral space. Both experimental measurements and analytical calculations show that each flux component plays a distinct dynamical role in energy and enstrophy transfer, indicating a link between features of triad interactions in spectral space and features of the spatial structure of the flow field. This link is further explored and supported by geometric considerations. In addition, this thesis also reports intriguing spatial ordering of the turbulent stress, which suggests future research toward identifying spatial flow structures with dynamical significance.;Finally, a new method for predicting and modeling flow dynamics based on Lagrangian averaging is discussed, with results that suggest a relation between the filtered Okubo--Weiss parameter and the dynamics of the flow averaged along Lagrangian trajectories. This link is explained by noting that Lagrangian averaging acts as a coherence filter. |
