1. A system for controlling the flow of a medium across or through a region constrained by a primary solid that interferes with the flow of the medium, the system comprising: at least one sensor located in proximity to the primary solid for measuring and quantifying at least one flow parameter of the medium; a processor coupled to the at least one sensor for calculating a time-varying measure of relative patternness for the medium in proximity to the primary solid, the measure of relative patternness including a quantification of approximate entropy; and a secondary solid responsive to the time-varying measure of relative patternness to affect the flow of the medium in proximity to the primary solid.