• what does these wrong messages mean in Feflow?

    I am using Feflow 7. and there are several wrong messages shown when running the models which I don't know why that happened.
    I am running a 2D modeling of Dam seepage.

    1.'No convergence in Picard iteration at time 2.8.. with remaining residual 2.0..e-2 greater than 1.0 e-2.'
    This message shown when I using mixed based form of Richard equation, and I tried to use a smaller error tolerance, but it doesn't work

    2. 'Time step reduction at t=317... is given up after 12 cycles of rejections.'

    3.' Time-series 4: the value of the last point must not differ from the value of the first point for cyclic time series! resetting to non-cyclic mode...
    this happened every time when I import the time series. I don't choose a cyclic mode, but I don't know why this message showed.

    Please kindly to help me.
  • How to assign upstream hydraulic head boundary for a dam seepage modeling

    I am doing a dam seepage modeling and feel confused about how to set the hydraulic head boundary for the upstream face of the dam.
    I have reservoir level data varies with time as a function of h(t) which can be used as 1st type (Dirichlet) boundary. However, as reservoir level varies a lot in a year, can be 7m differences, this will make some nodes at the upstream boundary exposed to the air some time.
    For eg. if the reservoir level varies from elevation 30'-37', and I set the nodes which have elevation from 0-37' as the upstream boundary. In this case, for the nodes between 30'-37', like 35', it may exposed  to the air. So I just wondering, for the nodes between 30'-37', do I need to add some constraints or do some other treatments? or only a 1st type boundary is enough for this case.

    Because this make me thinking about the seepage face which should be used for the downstream face boundary, it has a constraint Qmax=0 to prevent inflow. The free surface also varies at the boundary. But I am not sure what I can do with the upstream boundary.

    I will be appreciated for any help.