Calculation of the vertical shear (Source File: shear.F90)


INTERFACE:

    subroutine shear(nlev,cnpar)
DESCRIPTION:

The (square of the) shear frequency is defined as

$\displaystyle M^2 = \left( \dfrac{\partial {U}}{\partial {z}} \right)^2 + \left( \dfrac{\partial {V}}{\partial {z}} \right)^2 \quad .$ (36)

It is an important parameter in almost all turbulence models. The $ U$- and $ V$-contributions to $ M^2$ are computed using a new scheme which guarantees conservation of kinetic energy for the convertion from mean to turbulent kinetic energy, see Burchard (2002a). With this method, the discretisation of the $ U$-contribution can be written as

$\displaystyle \left( \dfrac{\partial {U}}{\partial {z}} \right)^2 \approx \frac{(\bar U_{j+1}-\bar U_j) (\tilde U_{j+1}-\tilde U_j)}{(z_{j+1}-z_j)^2}$ (37)

where $ \tilde U_j=\frac12(\hat U_j+U_j)$. The $ V$-contribution is computed analogously. The shear obtained from (37) plus the $ V$-contribution is then used for the computation of the turbulence shear production, see equation (146).


USES:

    use meanflow,   only: h,u,v,uo,vo
    use meanflow,   only: SS,SSU,SSV
 
    IMPLICIT NONE
INPUT PARAMETERS:
 
    number of vertical layers
    integer,  intent(in)                :: nlev
 
    numerical "implicitness" parameter
    REALTYPE, intent(in)                :: cnpar
REVISION HISTORY:
    Original author(s): Lars Umlauf
    $Log: shear.F90,v $
    Revision 1.1  2005-06-27 10:54:33  kbk
    new files needed

Karsten Bolding 2012-01-24