Seiche (source code)
= Seiche
A <seiche> is a standing oscillation of water in an enclosed or partly enclosed basin. A disturbance can displace water toward one end; restoring gravity and reflection at boundaries then support repeated oscillation. Wind and atmospheric-pressure changes can excite such motion in natural basins.<What is a seiche? by National Oceanic and Atmospheric Administration>[Standing-wave definition, basin examples and wind-driven excitation]{ref}
For an ideal straight basin of length $L$, uniform shallow depth $h$ and two closed ends, no normal flow at the walls gives surface-displacement modes proportional to $\cos(m\pi x/L)$. The <shallow-water dispersion relation> then gives $\omega_m=m\pi\sqrt{gh}/L$ for $m=1,2,\ldots$. The fundamental period is $T_1=2L/\sqrt{gh}$.
An illustrative model with $L=2\,\mathrm m$, $h=0.10\,\mathrm m$ and $g=9.81\,\mathrm{m\,s^{-2}}$ gives $T_1\simeq4.04\,\mathrm s$. A gently disturbed tank can test the period. Variable depth, open connections, friction and finite wave amplitude modify this ideal prediction.
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