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YB and Mike Cullen Rigorous derivation of the x z semigeostrophic equations pdf final version in CMS

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Niveau: Supérieur, Doctorat, Bac+8
RIGOROUS DERIVATION OF THE X-Z SEMIGEOSTROPHIC EQUATIONS ? YANN BRENIER † AND MIKE CULLEN ‡ Abstract. We prove that smooth solutions of the semigeostrophic equations in the incompress- ible x?z setting can be derived from the Navier-Stokes equations with the Boussinesq approximation. Key words. Atmospheric sciences, fluid mechanics, asymptotic analysis subject classifications AMS 86A10 (35Q35 76B99 86A05). 1. Introduction We consider the Navier-Stokes equations with the Boussinesq approximation (NSB): ?(∂tv+(v ·?)v)+?Kv+?p= y, ?·v=0, (1.1) ∂ty+(v ·?)y=G(x,y), (1.2) where x?D, D being a smooth bounded domain in Rd (d=2,3), v= v(t,x)?Rd is the velocity field, p=p(t,x) is the pressure field, y= y(t,x)?Rd is a vector-valued forcing term, G(x,y) is a given smooth vector-valued source term D?Rd?Rd, ?,?>0 are scaling factors and K is the linear dissipative operator Kv=?∆v. We assume that the fluid sticks to the boundary: v=0 along ∂D. We now consider the formal limit of these equations obtained by dropping the inertia term and the dissipative term (i.

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RIGOROUS DERIVATION OF THE XZ SEMIGEOSTROPHIC EQUATIONS † ‡ YANN BRENIERANDMIKE CULLEN
Abstract.We prove that smooth solutions of the semigeostrophic equations in the incompress iblexzsetting can be derived from the NavierStokes equations with the Boussinesq approximation.
Key words.Atmospheric sciences, fluid mechanics, asymptotic analysis subject classifications AMS 86A10 (35Q35 76B99 86A05).
1. Introduction We consider the NavierStokes equations with the Boussinesq approximation (NSB): ǫ(tv+ (v∙ ∇)v) +αKv+p=y,∇ ∙v= 0,(1.1)
ty+ (v∙ ∇)y=G(x, y),(1.2) d d wherexD,Dbeing a smooth bounded domain inR(d= 2,3),v=v(t, x)Ris the d velocity field,p=p(t, x) is the pressure field,y=y(t, x)Ris a vectorvalued forcing d d term,G(x, y) is a given smooth vectorvalued source termD×RR,ǫ, α >0 are scaling factors andKis the linear dissipative operatorKv=Δv. Weassume that the fluid sticks to the boundary:v= 0along∂D. We now consider the formal limit of these equations obtained by dropping the inertia term and the dissipative term (i.e.settingε=α= 0)in the NSB equations. p=y,∇ ∙v= 0, v//∂D,(1.3)
ty+ (v∙ ∇)y=G(x, y).(1.4) We are going to show that these equations can be justified under a strong uniform convexity assumption on the pressure fieldpsituation of interest in this paper. The is the case whendand the source term= 2 G(x, y) = (x2, y1x1).(1.5) Then (1.31.4) are the semigeostrophic Eady model equations in the special incom pressible “xzBy” situation.xz, we mean thatDis part of a vertical section, the second coordinatex2of each pointx= (x1, x2)DThe sourcebeing the vertical one. term in (1.5) represents the effect of the missing third dimension.In this identifica tion,yrepresents the effects of rotation and stratification, and the relationp=yin (1.3) expresses geostrophic and hydrostatic balance. The semigeostrophic model was considered by Hoskins [Ho] to model front for mations in atmospheric sciences.The Eady model is defined in chapter 6 of [Cu], and models a quasiperiodic evolution in which fronts form and decay.There has been CNRS,FR2800,Universit´edeNice,Mathe´matiques,ParcValroseFR06108Nice,France(brenier@unice.fr). Met Office, Exeter, UK (mike.cullen@metoffice.gov.uk). 1