A few thoughts on proper orthogonal decomposition in turbulence

Proper orthogonal decomposition was originally introduced in turbulence to identify large-scale patterns in turbulent flows. Over the years, several extensions have been formulated in order to strengthen its model-predictive abilities, with limited success in the case of fully developed turbulence. We argue that physics-based insight obtained from the proper orthogonal decomposition structures and other turbulence analysis techniques could lead to significant developments in that respect. Numerical results from channel flow simulations are used to illustrate our conjectures.