Opened 5 years ago
Last modified 4 years ago
#2237 closed Bug
no/partial/strong slip condition is actually free slip in one-point straits — at Version 1
Reported by: | davestorkey | Owned by: | davestorkey |
---|---|---|---|
Priority: | low | Milestone: | Unscheduled |
Component: | LBC | Version: | |
Severity: | minor | Keywords: | momentum boundary slip |
Cc: |
Description (last modified by nicolasmartin)
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Context
Analysis
The boundary condition on velocities tangential to topography is set via the value of fmask initialised in dom_msk as follows (NEMO 4 code):
Calculate from tmask:
fmask(ji,jj,jk) = tmask(ji,jj ,jk) * tmask(ji+1,jj ,jk) & & * tmask(ji,jj+1,jk) * tmask(ji+1,jj+1,jk)
Apply slip condition:
IF( rn_shlat /= 0 ) THEN ! Not free-slip lateral boundary condition ! ALLOCATE( zwf(jpi,jpj) ) ! DO jk = 1, jpk zwf( : , : ) = fmask(:,:,jk) DO jj = 2, jpjm1 DO ji = fs_2, fs_jpim1 ! vector opt. IF( fmask(ji,jj,jk) == 0._wp ) THEN fmask(ji,jj,jk) = rn_shlat * MIN( 1._wp , MAX( zwf(ji+1,jj), zwf(ji,jj+1), & & zwf(ji-1,jj), zwf(ji,jj-1) ) ) ENDIF END DO END DO
This selects fmask points at the topography-sea boundary by looking for points where fmask is zero but has a neighbouring fmask which is one. But this criterion doesn't work for single-point channels. A better criterion would be to check the neighbouring umask and vmask values:
Instead of:
MAX( zwf(ji+1,jj), zwf(ji,jj+1),zwf(ji-1,jj), zwf(ji,jj-1) )
this would be better:
MAX( umask(ji,jj,jk), umask(ji,jj+1,jk), vmask(ji,jj,jk), vmask(ji+1,jj,jk) )
Maybe this was deliberate? But if you want no-slip with free-slip in channels it is probably better to do that explicitly via a spatially varying shlat parameter.
Fix
...
Commit History (3)
Changeset | Author | Time | ChangeLog |
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13271 | clem | 2020-07-08T16:53:09+02:00 | counterpart of ticket #2237 for sea-ice |
13270 | clem | 2020-07-08T16:41:20+02:00 | should solve ticket #2237 |
10648 | davestorkey | 2019-02-07T16:57:16+01:00 | UKMO dev_r10037_shlat2d branch: bug fix - make sure modified shlat values are applied to single-point channels. (This fix relates to ticket #2237). |