User Forum of Software BASEMENT

Eva Ammann

User

Registered: 2021-08-26

Posts: 6

Error mass balance - Rainfall

Dear Basement Community,

I am trying to model a rainfall event in the city of Bern. When I try to do the simulation with the rainfall as external source, I always get a lot of mass balance problems and the simulation has to be aborted. However, if I let water flow in through a inflow.txt file everything works fine.

My model.json looks like this with the rainfall:
{
  "SETUP": {
    "DOMAIN": {
      "BASEPLANE_2D": {
        "GEOMETRY": {
          "REGIONDEF": [
            {
              "index": [
                0
              ],
              "name": "zero"
            },
            {
              "index": [
                1
              ],
              "name": "one"
            },
            {
              "index": [
                2
              ],
              "name": "two"
            },
            {
              "index": [
                3
              ],
              "name": "three"
            }
          ],
          "STRINGDEF": [
            {
              "name": "Gleis",
              "upstream_direction": "left"
            },
            {
              "name": "Depotstrasse",
              "upstream_direction": "left"
            },
            {
              "name": "Stadtbachstrasse_West",
              "upstream_direction": "left"
            },
            {
              "name": "Inflow",
              "upstream_direction": "left"
            }
          ],
          "mesh_file": "Test_LG_West_computational-mesh_v8.2dm"
        },
        "HYDRAULICS": {
          "BOUNDARY": {
            "STANDARD": [
              {
                "name": "Gleis",
                "string_name": "Gleis",
                "type": "zero_gradient_out"
              },
              {
                "name": "Depotstrasse",
                "string_name": "Depotstrasse",
                "type": "zero_gradient_out"
              },
              {
                "name": "Stadtbachstrasse_West",
                "string_name": "Stadtbachstrasse_West",
                "type": "zero_gradient_out"
              }
            ]
          },
          "FRICTION": {
            "default_friction": 30,
            "type": "strickler"
          },
          "INITIAL": {
            "type": "dry"
          },
          "PARAMETER": {
            "CFL": 0.5,
            "fluid_density": 1000.0,
            "max_time_step": 100.0,
            "minimum_water_depth": 0.01,
            "safe_mode": "off"
          },
          "SOURCE": [
            {
              "data": 20.0,
              "name": "Rainfall_for_MATID_zero",
              "region_name": "zero",
              "sink": "exact",
              "type": "distributed"
            },
            {
              "data": 20.0,
              "name": "Rainfall_for_MATID_one",
              "region_name": "one",
              "sink": "exact",
              "type": "distributed"
            },
            {
              "data": 20.0,
              "name": "Rainfall_for_MATID_two",
              "region_name": "two",
              "sink": "exact",
              "type": "distributed"
            },
            {
              "data": 20.0,
              "name": "Rainfall_for_MATID_three",
              "region_name": "three",
              "sink": "exact",
              "type": "distributed"
            }
          ]
        }
      },
      "PHYSICAL_PROPERTIES": {
        "gravity": 9.81
      }
    },
    "simulation_name": "RUNFILE"
  }
}

Is there an obvious mistake with my defined rainfall?

Thank you for your help,
Eva

Lukas Vonwiller

Developer

Registered: 2014-09-04

Posts: 130

Re: Error mass balance - Rainfall

hi Eva

you add exactly the same amount of water/rainfall using the inflow.txt, e.g. 20.0?
Does the 'minimum_water_depth' change the behavior of the simulation?

cheers,
Lukas

Eva Ammann

User

Registered: 2021-08-26

Posts: 6

Re: Error mass balance - Rainfall

Yes, well I had to recalculate it. If I understand correctly, the inflow.txt file for the hypothetical river is in m3/s and the rainfall as external source is in mm/h. If that is true, then the mass balance problems also occur even if I use the same total amount of water that will enter the system during the rainfall event.

Cheers,
Eva