Gelombang graviti: Perbezaan antara semakan
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{{about|pergerakan bendalir|fenomena relativiti am | Gelombang graviti}}
[[Image:Waves.jpg|thumb|right|180px|Gelombang graviti permukaan, memecah di pantai lautan.]]
[[Image:wave clouds.jpg|thumb|right|180px|Gelombang awan di atas [[Theresa, Wisconsin]], Amerika Syarikat.]]
[[Image:GravityWaves ArabianSea.MODIS.2005may23.jpg|right|180px|thumb|Gelombang graviti atmosfera yang dilihat dari ruang angkasa.]]
Dalam [[dinamik bendalir]], '''glombang graviti''' ialah gelombang yang dijana dalam medium [[bendalir]] atau pada [[Antara muka (jirim)|antara muka]] antara dua medium apabila [[Daya (fizik)|daya]] [[graviti]] atau [[keapungan]] cuba mengembalikan keseimbangan. Contoh antara muka sedemikian ialah antara [[Atmosfera Bumi|atmosfera]] dan [[lautan]], yang menimbulkan [[gelombang angin]].
A gravity wave results when fluid is displaced from a position of [[mechanical equilibrium|equilibrium]]. The restoration of the fluid to equilibrium will produce a movement of the fluid back and forth, called a ''wave orbit''.<ref>{{Citation | publisher = Cambridge University Press | isbn = 9780521010450 | last = Lighthill | first = James |author-link = James Lighthill | title = Waves in fluids | year = 2001 | page = 205 }}</ref> Gravity waves on an air–sea interface of the ocean are called '''surface gravity waves''' or [[surface wave]]s, while gravity waves that are ''within'' the body of the water (such as between parts of different densities) are called [[internal wave]]s. [[Wind wave|Wind-generated waves]] on the water surface are examples of gravity waves, as are [[tsunami]]s and ocean [[tide]]s.
Wind-generated gravity waves on the [[free surface]] of the Earth's ponds, lakes, seas and oceans have a period of between 0.3 and 30 seconds (3 Hz to 0.03 Hz). Shorter waves are also affected by [[surface tension]] and are called [[capillary wave#Gravity–capillary waves|gravity–capillary wave]]s and (if hardly influenced by gravity) [[capillary wave]]s. Alternatively, so-called [[infragravity wave]]s, which are due to [[undertone series|subharmonic]] [[nonlinear system|nonlinear]] wave interaction with the wind waves, have periods longer than the accompanying wind-generated waves.<ref>{{Citation
| last1 = Bromirski
| first1 = Peter D.
| first2 = Olga V.
| last2 = Sergienko
| first3 = Douglas R.
| last3 = MacAyeal
| title = Transoceanic infragravity waves impacting Antarctic ice shelves
| journal = Geophysical Research Letters
| volume = 37
| issue = L02502
| publisher = [[American Geophysical Union]]
| location =
| year = 2010
| doi = 10.1029/2009GL041488
| postscript = .
| bibcode=2010GeoRL..3702502B}}</ref>
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