Estuary_test: are sediment size units and output critical stress right?

[stevenmiguelfigueroa]

Hi, I'm a new user of ROMS. I'm using version 3.7. I'm analyzing the default sed_toy and estuary_test test cases for practice. I noticed some differences in sediment size and the critical stresses between the log file and the output ocean_his.nc. Here is a copy of part of the log file:

Sediment Parameters, Grid: 01
=============================


Size Sd50 Csed Srho Wsed Erate poros
Class (mm) (kg/m3) (kg/m3) (mm/s) (kg/m2/s) (nondim)

1 1.5000E-01 0.0000E+00 2.6500E+03 5.0000E-01 1.0000E-04 9.0000E-01

tau_ce tau_cd nl_tnu2 nl_tnu4 Akt_bak Tnudg
(N/m2) (N/m2) (m2/s) (m4/s) (m2/s) (day)

1 5.0000E-02 5.0000E-02 0.0000E+00 0.0000E+00 5.0000E-06 0.0000E+00

morph_fac
(nondim)

1 1.0000E+00

The size, Sd50, is 0.15 mm. In the ocean_his.nc file, reading Sd50 gives 0.00015 mm. So, I think the units in the .nc file should be meters and not mm.

Also, above it can be seen tau_ce = 0.05 N m^-2, which is the expected value. In the .nc file, it is found to be tau_ce = 0.000048 N m^-2.
Alternatively, looking at erosion_stress in the output .nc file shows the expected value. But unexpectedly there spikes in time to a value of 1028 N m^-2, the same numerical value as the density of seawater. Plots showing this are attached for a erosion_stress vs. time at a point and erosion_stress vs. time and along-channel distance as a pcolor plot.

The times series shows marked at the bottom a sampled point with the expected critical stress for erosion (Y = 0.05). The pcolor plot shows unexpected structure for the along-channel erosion_stress, and that the spikes are affecting much of the domain.

[jcwarner]

sorry for the late reply.
i looked into this and the values written to the his files are ok, but the units may not be.
The stresses tau_ce tau_cd are /rho when read, so they are written out as m2/s2. so it should say m2/s2 in the his nc file.
The Sd50 is read in and converted to m, so that should also say meters.
For the erosion stress high values, i noticed the estaury tests is now set out with

# elif defined ESTUARY_TEST
DO j=JstrT,JendT
DO i=IstrT,IendT
!
! Set bed layer properties.
!
DO k=1,Nbed
bed(i,j,k,iaged)=time(ng)
bed(i,j,k,ithck)=0.001_r8
bed(i,j,k,iporo)=0.90_r8

so the 1 mm initial bed thickness is not enough for that system. you can change it to be 1.00 m or something, just to get some realistic values.
When the sed erodes away, the erosion stress gets high, but it is not doing anything since there is no sediment at that cell, so it does not matter.
i will make that be zero or something realistic.
-j