• MIKE3-Instability : water surface oscillations in upstream boundary of a channel

    Hello every body,

    I am running a physical model, a channel scaled 1/6000 in XY plane and 1/400 in Z direction, with MIKE3D. the characteristics of the model are:

    0- channel bathymetry is not the same along the channel: maximum depth: 15cm, maximum width: 12 cm and length : 3-4 meter
    1- Ten vertical sigma variable layers and rectangular mesh.
    2- 10000, 0.01 sec timesteps
    3-Navier Stokes-equations
    4- minimum and maximum time steps: 0.0001, 0.01 sec
    5- Riemann factor and filter coefficient: 1, 0.02
    6-Drying/wetting depth: 0.001, 0.002 m
    7- Minimum and Maximum eddy viscosities: 2.25e-10 , 0.000125 m2/s
    8- Roughness height: 2.425e-05 m
    9- Upstream and downstream boundary conditions: 0.000707 m3/s and 0.0054 m
    10- initial condition: water surface elevation: 0.0054 m
    11- TKE and Dissipation of TKE in upstream and downstream boundaries: 3.75e-09 m2/s2 and 5.625e-09 m2/s3

    When I ran the model under above conditions, there is a huge oscillation/fluctuation of water surface in upstream boundary of the channel. This causes the model NOT to get stable.
    Any comments/help/guide would be appreciated.
    Regards