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Commit d565fa8b authored by Sibylle Techene's avatar Sibylle Techene
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Update section 3 of chap_DYN.tex it concerns up3 mostly

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...@@ -165,6 +165,10 @@ Note also that the $k$-axis is re-orientated downwards in the \fortran\ code com ...@@ -165,6 +165,10 @@ Note also that the $k$-axis is re-orientated downwards in the \fortran\ code com
the indexing used in the semi-discrete equations such as \autoref{eq:DYN_wzv} the indexing used in the semi-discrete equations such as \autoref{eq:DYN_wzv}
(see \autoref{subsec:DOM_Num_Index_vertical}). (see \autoref{subsec:DOM_Num_Index_vertical}).
When \np[=.true.]{ln_zad_Aimp}{ln\_zad\_Aimp},
a proportion of the vertical advection can be treated implicitly depending on the Courant number.
This option can be useful when the value of the timestep is limited by vertical advection \citep{lemarie.debreu.ea_OM15}.
%% ================================================================================================= %% =================================================================================================
\section{Coriolis and advection: vector invariant form} \section{Coriolis and advection: vector invariant form}
\label{sec:DYN_adv_cor_vect} \label{sec:DYN_adv_cor_vect}
...@@ -208,29 +212,6 @@ In the case of ENS, ENE or MIX schemes the land sea mask may be slightly modifie ...@@ -208,29 +212,6 @@ In the case of ENS, ENE or MIX schemes the land sea mask may be slightly modifie
vorticity term with analytical equations (\np[=.true.]{ln_dynvor_con}{ln\_dynvor\_con}). vorticity term with analytical equations (\np[=.true.]{ln_dynvor_con}{ln\_dynvor\_con}).
The vorticity terms are all computed in dedicated routines that can be found in the \mdl{dynvor} module. The vorticity terms are all computed in dedicated routines that can be found in the \mdl{dynvor} module.
% energy conserving scheme at T-point
%% =================================================================================================
\subsubsection[Energy conserving scheme (\forcode{ln_dynvor_enT})]{Energy conserving scheme (\protect\np{ln_dynvor_enT}{ln\_dynvor\_enT})}
\label{subsec:DYN_vor_enT}
The kinetic energy conserving scheme (ENT scheme) conserves the global kinetic energy but not the global enstrophy.
It is given by:
\begin{equation}
\label{eq:DYN_vor_enT}
\left\{
\begin{aligned}
&+\frac{1}{e_{1u}\,e_{2u}\,e_{3u}} \, \overline{ \left( f^T + \overline{\overline{ \zeta }}^{\,i,j} \right)
e_{1t}\,e_{2t}\,e_{3t} \, \overline{v}^{\,j}}^{\,i+1/2} \\
&-\frac{1}{e_{1v}\,e_{2v}\,e_{3v}} \, \overline{ \left( f^T + \overline{\overline{ \zeta }}^{\,i,j} \right)
e_{1t}\,e_{2t}\,e_{3t} \, \overline{u}^{\,i}}^{\,j+1/2}
\end{aligned}
\right.
\end{equation}
% enstrophy conserving scheme % enstrophy conserving scheme
%% ================================================================================================= %% =================================================================================================
\subsubsection[Enstrophy conserving scheme (\forcode{ln_dynvor_ens})]{Enstrophy conserving scheme (\protect\np{ln_dynvor_ens}{ln\_dynvor\_ens})} \subsubsection[Enstrophy conserving scheme (\forcode{ln_dynvor_ens})]{Enstrophy conserving scheme (\protect\np{ln_dynvor_ens}{ln\_dynvor\_ens})}
...@@ -420,12 +401,6 @@ the change of KE due to the gradient of KE (see \autoref{apdx:INVARIANTS}). ...@@ -420,12 +401,6 @@ the change of KE due to the gradient of KE (see \autoref{apdx:INVARIANTS}).
\end{aligned} \end{aligned}
\right. \right.
\] \]
When \np[=.true.]{ln_dynzad_zts}{ln\_dynzad\_zts},
a split-explicit time stepping with 5 sub-timesteps is used on the vertical advection term.
This option can be useful when the value of the timestep is limited by vertical advection \citep{lemarie.debreu.ea_OM15}.
Note that in this case,
a similar split-explicit time stepping should be used on vertical advection of tracer to ensure a better stability,
an option which is only available with a TVD scheme (see \np{ln_traadv_tvd_zts}{ln\_traadv\_tvd\_zts} in \autoref{subsec:TRA_adv_tvd}).
%% ================================================================================================= %% =================================================================================================
\section{Coriolis and advection: flux form} \section{Coriolis and advection: flux form}
...@@ -454,9 +429,31 @@ It is given by: ...@@ -454,9 +429,31 @@ It is given by:
- \overline u ^{j+1/2}\delta_{j+1/2} \left[ {e_{1u} } \right] } \ \right) - \overline u ^{j+1/2}\delta_{j+1/2} \left[ {e_{1u} } \right] } \ \right)
\end{multline*} \end{multline*}
Any of the (\autoref{eq:DYN_vor_ens}), (\autoref{eq:DYN_vor_ene}) and (\autoref{eq:DYN_vor_een}) schemes can be used to % energy conserving scheme at T-point
%% =================================================================================================
\subsubsection[Energy conserving scheme (\forcode{ln_dynvor_enT})]{Energy conserving scheme (\protect\np{ln_dynvor_enT}{ln\_dynvor\_enT})}
\label{subsec:DYN_vor_enT}
The kinetic energy conserving scheme at T-point (ENT scheme) conserves the global kinetic energy but not the global enstrophy.
It is given by:
\begin{equation}
\label{eq:DYN_vor_enT}
\left\{
\begin{aligned}
&+\frac{1}{e_{1u}\,e_{2u}\,e_{3u}} \, \overline{ \left( f^T + \overline{\overline{ \zeta }}^{\,i,j} \right)
e_{1t}\,e_{2t}\,e_{3t} \, \overline{v}^{\,j}}^{\,i+1/2} \\
&-\frac{1}{e_{1v}\,e_{2v}\,e_{3v}} \, \overline{ \left( f^T + \overline{\overline{ \zeta }}^{\,i,j} \right)
e_{1t}\,e_{2t}\,e_{3t} \, \overline{u}^{\,i}}^{\,j+1/2}
\end{aligned}
\right.
\end{equation}
Any of the (\autoref{eq:DYN_vor_ens}), (\autoref{eq:DYN_vor_ene}), (\autoref{eq:DYN_vor_enT}) and (\autoref{eq:DYN_vor_een})
schemes can be used to
compute the product of the Coriolis parameter and the vorticity. compute the product of the Coriolis parameter and the vorticity.
However, the energy-conserving scheme (\autoref{eq:DYN_vor_een}) has exclusively been used to date. However, the energy-conserving schemes (\autoref{eq:DYN_vor_een} and \autoref{eq:DYN_vor_enT})
have exclusively been used to date.
This term is evaluated using either a leapfrog scheme or a RK3 scheme. This term is evaluated using either a leapfrog scheme or a RK3 scheme.
In the leapfrog case it is centred in time (\textit{now} velocity). In the leapfrog case it is centred in time (\textit{now} velocity).
In the RK3 case it is forward in time (\textit{before} velocity) at stage 1, In the RK3 case it is forward in time (\textit{before} velocity) at stage 1,
...@@ -486,9 +483,9 @@ The discrete expression of the advection term is given by: ...@@ -486,9 +483,9 @@ The discrete expression of the advection term is given by:
Two advection schemes are available: Two advection schemes are available:
a $2^{nd}$ order centered finite difference scheme, CEN2, a $2^{nd}$ order centered finite difference scheme, CEN2,
or a $3^{rd}$ order upstream biased scheme, UBS. or a $3^{rd}$ order upstream biased scheme, UP3.
The latter is described in \citet{shchepetkin.mcwilliams_OM05}. The latter is described in \citet{shchepetkin.mcwilliams_OM05}.
The schemes are selected using the namelist logicals \np{ln_dynadv_cen2}{ln\_dynadv\_cen2} and \np{ln_dynadv_ubs}{ln\_dynadv\_ubs}. The schemes are selected using the namelist logicals \np{ln_dynadv_cen2}{ln\_dynadv\_cen2} and \np{ln_dynadv_up3}{ln\_dynadv\_up3}.
In flux form, the schemes differ by the choice of a space and time interpolation to define the value of In flux form, the schemes differ by the choice of a space and time interpolation to define the value of
$u$ and $v$ at the centre of each face of $u$- and $v$-cells, \ie\ at the $T$-, $f$-, $u$ and $v$ at the centre of each face of $u$- and $v$-cells, \ie\ at the $T$-, $f$-,
and $uw$-points for $u$ and at the $f$-, $T$- and $vw$-points for $v$. and $uw$-points for $u$ and at the $f$-, $T$- and $vw$-points for $v$.
...@@ -515,17 +512,17 @@ produce a sensible solution. ...@@ -515,17 +512,17 @@ produce a sensible solution.
The associated time-stepping is performed using a leapfrog scheme in conjunction with an Asselin time-filter, The associated time-stepping is performed using a leapfrog scheme in conjunction with an Asselin time-filter,
so $u$ and $v$ are the \emph{now} velocities. so $u$ and $v$ are the \emph{now} velocities.
% UBS scheme % UP3 scheme
%% ================================================================================================= %% =================================================================================================
\subsubsection[UBS: Upstream Biased Scheme (\forcode{ln_dynadv_ubs})]{UBS: Upstream Biased Scheme (\protect\np{ln_dynadv_ubs}{ln\_dynadv\_ubs})} \subsubsection[UP3: Upstream Biased Scheme (\forcode{ln_dynadv_up3})]{UP3: Upstream Biased Scheme (\protect\np{ln_dynadv_up3}{ln\_dynadv\_up3})}
\label{subsec:DYN_adv_ubs} \label{subsec:DYN_adv_up3}
The UBS advection scheme is an upstream biased third order scheme based on The UP3 advection scheme is an upstream biased third order scheme based on
an upstream-biased parabolic interpolation. an upstream-biased parabolic interpolation.
For example, the evaluation of $u_T^{ubs} $ is done as follows: For example, the evaluation of $u_T^{up3} $ is done as follows:
\begin{equation} \begin{equation}
\label{eq:DYN_adv_ubs} \label{eq:DYN_adv_up3}
u_T^{ubs} =\overline u ^i-\;\frac{1}{6} u_T^{up3} =\overline u ^i-\;\frac{1}{6}
\begin{cases} \begin{cases}
u"_{i-1/2}& \text{if $\ \overline{e_{2u}\,e_{3u} \ u}^i \geqslant 0$ } \\ u"_{i-1/2}& \text{if $\ \overline{e_{2u}\,e_{3u} \ u}^i \geqslant 0$ } \\
u"_{i+1/2}& \text{if $\ \overline{e_{2u}\,e_{3u} \ u}^i < 0$ } u"_{i+1/2}& \text{if $\ \overline{e_{2u}\,e_{3u} \ u}^i < 0$ }
...@@ -542,28 +539,21 @@ As the scheme already includes a diffusion component, it can be used without exp ...@@ -542,28 +539,21 @@ As the scheme already includes a diffusion component, it can be used without exp
(\ie\ \np[=]{ln_dynldf_lap}{ln\_dynldf\_lap}\np[=.false.]{ln_dynldf_bilap}{ln\_dynldf\_bilap}), (\ie\ \np[=]{ln_dynldf_lap}{ln\_dynldf\_lap}\np[=.false.]{ln_dynldf_bilap}{ln\_dynldf\_bilap}),
and it is recommended to do so. and it is recommended to do so.
The UBS scheme is not used in all directions. The UP3 scheme is used in all directions.
In the vertical, the centred $2^{nd}$ order evaluation of the advection is preferred, \ie\ $u_{uw}^{ubs}$ and UP3 is diffusive and is associated with vertical mixing of momentum. \cmtgm{ gm pursue the
$u_{vw}^{ubs}$ in \autoref{eq:DYN_adv_cen2} are used.
UBS is diffusive and is associated with vertical mixing of momentum. \cmtgm{ gm pursue the
sentence:Since vertical mixing of momentum is a source term of the TKE equation... } sentence:Since vertical mixing of momentum is a source term of the TKE equation... }
For stability reasons, the first term in (\autoref{eq:DYN_adv_ubs}), For stability reasons, the first term in (\autoref{eq:DYN_adv_up3}),
which corresponds to a second order centred scheme, is evaluated using the \textit{now} velocity (centred in time), which corresponds to a second order centred scheme, is evaluated using the \textit{now} velocity (centred in time),
while the second term, which is the diffusion part of the scheme, while the second term, which is the diffusion part of the scheme,
is evaluated using the \textit{before} velocity (forward in time). is evaluated using the \textit{before} velocity (forward in time).
This is discussed by \citet{webb.de-cuevas.ea_JAOT98} in the context of the Quick advection scheme. This is discussed by \citet{webb.de-cuevas.ea_JAOT98} in the context of the Quick advection scheme.
Note that the UBS and QUICK (Quadratic Upstream Interpolation for Convective Kinematics) schemes only differ by Note that the UP3 and QUICK (Quadratic Upstream Interpolation for Convective Kinematics) schemes only differ by
one coefficient. one coefficient.
Replacing $1/6$ by $1/8$ in (\autoref{eq:DYN_adv_ubs}) leads to the QUICK advection scheme \citep{webb.de-cuevas.ea_JAOT98}. Replacing $1/6$ by $1/8$ in (\autoref{eq:DYN_adv_up3}) leads to the QUICK advection scheme \citep{webb.de-cuevas.ea_JAOT98}.
This option is not available through a namelist parameter, since the $1/6$ coefficient is hard coded. This option is not available through a namelist parameter, since the $1/6$ coefficient is hard coded.
Nevertheless it is quite easy to make the substitution in the \mdl{dynadv\_ubs} module and obtain a QUICK scheme. Nevertheless it is quite easy to make the substitution in the \mdl{dynadv\_up3} module and obtain a QUICK scheme.
Note also that in the current version of \mdl{dynadv\_ubs},
there is also the possibility of using a $4^{th}$ order evaluation of the advective velocity as in ROMS.
This is an error and should be suppressed soon.
\cmtgm{action : this have to be done}
%% ================================================================================================= %% =================================================================================================
\section[Hydrostatic pressure gradient (\textit{dynhpg.F90})]{Hydrostatic pressure gradient (\protect\mdl{dynhpg})} \section[Hydrostatic pressure gradient (\textit{dynhpg.F90})]{Hydrostatic pressure gradient (\protect\mdl{dynhpg})}
......
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