Changes between Version 1 and Version 2 of Ticket #590
- Timestamp:
- 05/22/13 01:04:07 (12 years ago)
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Ticket #590 – Description
v1 v2 1 Two new open boundary conditions have been added: 1) Explicit Chapman boundary condition s for free-surface, and 2) Shchepetkin boundary conditionsfor 2D momentum. Now, in ROMS standard input script '''ocean_*.in''' we have:1 Two new open boundary conditions have been added: 1) Explicit Chapman boundary condition for free-surface, and 2) Shchepetkin boundary condition for 2D momentum. Now, in ROMS standard input script '''ocean_*.in''' we have: 2 2 3 3 {{{ … … 49 49 }}} 50 50 51 * '''Explicit Chapman''' ('''Che''') '''boundary condition''': This explicit condition for free-surface is less dissipative and reflective than the Implicit Chapman ('''Cha'''). Anyway, the phase speed ('''Cx''','''Ce''') is bounded to be less than oneso there is not need for implicit treatment.51 * '''Explicit Chapman''' ('''Che''') '''boundary condition''': This explicit condition for free-surface is less dissipative and reflective than the Implicit Chapman ('''Cha'''). Anyway, the phase speed ('''Cx''','''Ce''') is bounded to be less than '''one''' so there is not need for implicit treatment. 52 52 53 * '''Shchepetkin''' ('''Shc''') '''boundary condition''': This is a better alternative to the so called Flather ('''Fla''') condition s for 2D momentum. The Flather boundary conditions are mentioned in Chapman (1985) paper but a derivation for a staggered grid is not presented. Actually, Flather (1976) discussed a radiation boundary condition (Equation 8) based on the Reid and Bodine (1968) relationship between elevation and currents at the boundary . Both Flather (1976) and Reid and Bodine (1968) papers are difficult to get. This may explain the misunderstanding. I read both papers recently. Many thanks to Sasha for providing a copy of these papers.53 * '''Shchepetkin''' ('''Shc''') '''boundary condition''': This is a better alternative to the so called Flather ('''Fla''') condition for 2D momentum. The Flather boundary condition is mentioned in Chapman (1985) paper but a derivation for a staggered grid is not presented. Actually, Flather (1976) discussed a radiation boundary condition (Equation 8) based on the Reid and Bodine (1968) relationship between elevation and currents at the boundary edge. Both Flather (1976) and Reid and Bodine (1968) papers are difficult to get. This may explain the misunderstanding and erroneous citation. I read both papers recently. Many thanks to Sasha for providing a copy of these papers. 54 54 55 Regardless if this boundary condition is attributed to Reid and Bodine (1968) or Flather (1976), it generates a instability when '''C=SQRT(g/h)=0.5'''. Sasha discussed this [http://www.myroms.org/Workshops/ROMS2007/presentations/Tuesday/Shchepetkin.pdf numerical instability] at the 2007 ROMS Workshop (UCLA). He also discussed a solution and reformulation of this boundary conditions. This boundary condition is discussed latter in Mason et al. (2010) paper.55 Regardless if this boundary condition is attributed to Reid and Bodine (1968) or Flather (1976), it generates an interesting instability when '''C=SQRT(g/h)=0.5'''. Sasha discussed this [http://www.myroms.org/Workshops/ROMS2007/presentations/Tuesday/Shchepetkin.pdf numerical instability] at the 2007 ROMS Workshop (UCLA). He also discussed a solution and reformulation of this boundary condition. This boundary condition is discussed latter in Mason et al. (2010) paper. 56 56 57 Sasha has been talking about this boundary condition for several years so I named here in ROMS after him. Many thanks to Sasha for implementing this more stable conditions and providing mehis code.57 Sasha has been talking about this boundary condition for several years so I named here in ROMS after him. Many thanks to Sasha for implementing this more stable conditions and providing us his code. 58 58 59 59 I also coded the '''TLM''', '''RPM''', and '''ADM''' versions of these boundary conditions. We are currently testing them.
