no stress bottom (#60)

* no stress bottom

* change name for calc_bottom_stress

Author: bderembl

src/meanflow/friction.F90

@@ -58,6 +58,7 @@ subroutine friction(nlev,kappa,avmolu,tx,ty,plume_type)
    use meanflow,      only: h,z0b,h0b,MaxItz0b,z0s,za
    use meanflow,      only: u,v,gravity
    use meanflow,      only: u_taub,u_taubo,u_taus,drag,taub
+   use meanflow,      only: calc_bottom_stress
    use meanflow,      only: charnock,charnock_val,z0s_min
 !
    IMPLICIT NONE
@@ -83,6 +84,8 @@ subroutine friction(nlev,kappa,avmolu,tx,ty,plume_type)
 !BOC
 
    drag = _ZERO_
+   rr_s = _ZERO_
+   rr_b = _ZERO_
 
 !  use the Charnock formula to compute the surface roughness
    if (charnock) then
@@ -92,32 +95,35 @@ subroutine friction(nlev,kappa,avmolu,tx,ty,plume_type)
       z0s=z0s_min
    end if
 
-   if (first) then
-      u_taub = u_taubo
-      first = .false.
-   else
-      u_taubo = u_taub
-   end if
-!  iterate bottom roughness length MaxItz0b times
-   do i=1,MaxItz0b
-
-      if (avmolu.le.0) then
-         z0b=0.03*h0b + za
+   if (calc_bottom_stress) then
+      if (first) then
+         u_taub = u_taubo
+         first = .false.
       else
-         z0b=0.1*avmolu/max(avmolu,u_taub)+0.03*h0b + za
+         u_taubo = u_taub
       end if
+!     iterate bottom roughness length MaxItz0b times
+      do i=1,MaxItz0b
 
-!     compute the factor r (version 1, with log-law)
-      rr_b=kappa/(log((z0b+h(1)/2)/z0b))
+         if (avmolu.le.0) then
+            z0b=0.03*h0b + za
+         else
+            z0b=0.1*avmolu/max(avmolu,u_taub)+0.03*h0b + za
+         end if
 
-!     compute the factor r (version 2, with meanvalue log-law)
-!     frac=(z0b+h(1))/z0b
-!     rr=kappa/((z0b+h(1))/h(1)*log(frac)-1.)
+!        compute the factor r (version 1, with log-law)
+         rr_b=kappa/(log((z0b+h(1)/2)/z0b))
 
-!     compute the friction velocity at the bottom
-      u_taub = rr_b*sqrt( u(1)*u(1) + v(1)*v(1) )
+!        compute the factor r (version 2, with meanvalue log-law)
+!        frac=(z0b+h(1))/z0b
+!        rr=kappa/((z0b+h(1))/h(1)*log(frac)-1.)
+
+!        compute the friction velocity at the bottom
+         u_taub = rr_b*sqrt( u(1)*u(1) + v(1)*v(1) )
+
+       end do
+   end if
 
-   end do
 !  compute the factor r (version 1, with log-law)
    if (plume_type .eq. 1) rr_s=kappa/(log((z0s+h(nlev)/2)/z0s))
 

src/meanflow/meanflow.F90

@@ -90,6 +90,7 @@ module meanflow
 
 !  the 'meanflow' configuration
    REALTYPE, public                    :: h0b
+   logical,  public                    :: calc_bottom_stress
    REALTYPE, public                    :: z0s_min
    logical,  public                    :: charnock
    REALTYPE, public                    :: charnock_val
@@ -168,6 +169,8 @@ subroutine init_meanflow_yaml()
    LEVEL1 'init_meanflow_yaml'
 
    branch => settings_store%get_typed_child('bottom')
+   call branch%get(calc_bottom_stress, 'calc_bottom_stress', 'compute bottom stress (default: true)', &
+                   default=.true.)
    call branch%get(h0b, 'h0b', 'physical bottom roughness', 'm', &
                 minimum=0._rk,default=0.05_rk, description='physical bottom roughness or bed roughness. This variable, h0b, relates to the hydrodynamic bottom roughness z0b as z0b = 0.03*h0b + 0.1*nu/ustar.')
    call branch%get(MaxItz0b, 'max_it_z0b', 'number of iterations for hydrodynamic bottom roughness', &
@@ -238,6 +241,7 @@ subroutine post_init_meanflow(nlev,latitude)
 !  Initialize bottom and surface stress to zero
 !  They will be set in friction, but also used as input in the same routine.
    u_taub = _ZERO_
+   u_taubo = _ZERO_
    u_taus = _ZERO_
    taub = _ZERO_
 
@@ -551,7 +555,7 @@ subroutine print_state_meanflow()
       grid_method,c1ad,c2ad,c3ad,c4ad,Tgrid,NNnorm, &
       SSnorm,dsurf,dtgrid,grid_file,gravity,        &
       rotation_period,rho_0,avmolu,avmolT, avmolS,  &
-      MaxItz0b,no_shear
+      MaxItz0b,no_shear,calc_bottom_stress
 
    LEVEL2 'z0b,z0s,za',z0b,z0s,za
    LEVEL2 'cori',cori