Time-Dependence and Shocks
None of the hydraulically driven oceanic or atmospheric flows discussed in the introduction to this book are steady, and very few are approximately so. A~striking example of unsteadiness was discovered by Worthington (1969) who, in 1967, placed an array of 30 moored current meters in the Denmark Strait in order to measure the deep velocities of the overflow. When Worthington returned a year later he found that all but one of the instruments had been destroyed or could not be recovered. The surviving current meter showed a history of rapid velocity fluctuations ranging from near zero to 1.4 m/s, most likely due to the meandering of the edge of the jet-like overflow back and forth across the instrument. Worthington concluded “the currents associated with the overflow water were too strong on this occasion to be measured using existing mooring technology”.
KeywordsFroude Number Potential Vorticity Shallow Water Equation Hydraulic Jump Left Wall
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