Compact approximations to the bottom friction term, for the study of tides propagating in channels

摘要: Abstract Approximations to the bottom friction term Ku | u |/( H + Z ), found in equations of tidal hydrodynamics, are presented, taking fully into account its nonlinear character. In upstream regions where current no longer reverses, becomes 2 0 1 / as a first approximation, being steady current, oscillatory contribution. A two-term approximation reproduces quadratic variation field term, zones reverses: this suffices predict and understand peculiarities damping incoming components, associated with friction. It also helps identify evaluate compound harmonics which result from their frictional interactions. three-term should be applied when numerical accuracy necessary. The approximations described have already shown themselves most helpful understanding effects phenomena.