The known unknowns of hydraulic engineering

Hydraulic engineers and researchers deal with the scientific challenges presented by turbulent flow and its interactions with the surroundings. Turbulent flows are characterised by unpredictable behaviour, and, as yet, little systematic research has been conducted in natural systems. This paper discusses the implications of recent developments in affordable instrumentation, which was previously characterised by intrinsic weaknesses that adversely affected the quality of the signal outputs. A challenging application is the unsteady turbulence field in tidal bores. The interactions between open channel flows and movable boundaries and the atmosphere illustrate another aspect of our limited knowledge. Rapid siltation of reservoirs and air entrainment in turbulent free-surface flows are discussed. In both applications, hydraulic engineers require some broad-based expertise. In turn, the education of future hydraulic engineers is of vital importance