[MITgcm-support] adding uniform background flow to all water grid points smoothly.

[Li Jianing]

Hi again, the former e-mail is broken and I have
no idea. So I'm re-sending it from  my phone, hope this works. Here is the message:

Hi there,

 I'm trying to add a uniform background flow field (U=0.1m/s) to my 2D (x-z) simulation, which is laterally homogeneous and vertically uniformly stratified. To avoid obvious noise induced by flow-topography interaction, I hope the background flow field firstly grow slowly and then remain stable.
 I tried to use U_init+OBCS or RBCS to do that, but the results seem not so reasonable. I think the better way is to apply an additional forcing to the rhs of momentum equation (x: -fV; y: fU). So I altered the 'myPa_TendVelV' to fU in '/pkg/mypackage/mypackage_init_varia.F' and enabled this package and run for 12 hours. The result shows a gorwing U field (0 to 0.03m/s or so generally, bigger or smaller values at topography) but didn't reach 0.1 m/s at the end (12hr modeltime).
So,
  1. Is this a right way to adding uniform background field, any way to do this easier?
  2. By RBCS relaxing the flow field also makes U grow gradually from 0 to ~0.1. These show dramatic distinct patterns, which is more reasonable ?

Thanks.
Jianing Li

&&&this is how I modified 'mypackage'&&&
# mypackage_init_varia.F:
line 50: myPa_TendVelV (i,j,k,bi,bj) = 4.E-6

# MYPACKAGE_OPTIONS.h
line 14: #undef MYPACKAGE_2D_STATE

#data.mypackage(whole file):
&MYPACKAGE_PARM01
myPa_MNC=.FALSE.,
myPa_applyTendU=.TRUE.,
myPa_applyTendV=.TRUE.,
 &


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