Nappe Oscillation

by H. Ivan Schwartz,

Serial Information: Journal of the Hydraulics Division, 1964, Vol. 90, Issue 6, Pg. 129-143

Document Type: Journal Paper


Sheets of water discharging freely from long weirs or spillways such as those on dams raised by stressing cables may exhibit the undesirable phenomenon of nappe oscillation, unless split at frequent intervals by suitable splitters. Tremendous noise is generated and structural damage to mechanical appurtenances may result where the water spills over crest gates. A theory is advanced to show that the air beneath the nappe vibrates at one of a particular set of frequencies, depending on certain nonlinear characteristics. Some aspects of the mechanism are examined in detail and it is shown that a range of possible frequencies can be determined if the initial velocity, height of fall, and angle of projection are know. The influence of damping is briefly examined.

Subject Headings: Cables | Spillways | Oscillations | Water discharge | Wave crest | Sheets | Weirs | Dams

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