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In mathematical physics, the Whitham equation is a non-local model for non-linear dispersive waves: : This integro-differential equation for the oscillatory variable ''η''(''x'',''t'') is named after Gerald Whitham who introduced it as a model to study breaking of non-linear dispersive water waves in 1967. For a certain choice of the kernel ''K''(''x'' − ''ξ'') it becomes the Fornberg–Whitham equation. ==Water waves== * For surface gravity waves, the phase speed ''c''(''k'') as a function of wavenumber ''k'' is taken as:〔 :: while :with ''g'' the gravitational acceleration and ''h'' the mean water depth. The associated kernel ''K''ww(''s'') is:〔 :: * The Korteweg–de Vries equation emerges when retaining the first two terms of a series expansion of ''c''ww(''k'') for long waves with :〔 :: :with ''δ''(''s'') the Dirac delta function. * Bengt Fornberg and Gerald Whitham studied the kernel ''K''fw(''s'') – non-dimensionalised using ''g'' and ''h'': :: and with :The resulting integro-differential equation can be reduced to the partial differential equation known as the Fornberg–Whitham equation:〔 :: :This equation is shown to allow for peakon solutions – as a model for waves of limiting height – as well as the occurrence of wave breaking (shock waves, absent in e.g. solutions of the Korteweg–de Vries equation).〔〔 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Whitham equation」の詳細全文を読む スポンサード リンク
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