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Propagating and evanescent internal waves in a deep ocean model
We present experimental and computational studies of the propagation of
internal waves in a stratified fluid with an exponential density profile that
models the deep ocean. The buoyancy frequency profile (proportional to
the square root of the density gradient) varies smoothly by more than an order
of magnitude over the fluid depth, as is common in the deep ocean. The
nonuniform stratification is characterized by a turning depth , where
is equal to the wave frequency and .
Internal waves reflect from the turning depth and become evanescent below the
turning depth. The energy flux below the turning depth is shown to decay
exponentially with a decay constant given by , which is the horizontal
wavenumber at the turning depth. The viscous decay of the vertical velocity
amplitude of the incoming and reflected waves above the turning depth agree
within a few percent with a previously untested theory for a fluid of arbitrary
stratification [Kistovich and Chashechkin, J. App. Mech. Tech. Phys. 39,
729-737 (1998)].Comment: 13 pages, 4 figures, 4 table
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