Skip to content

Boundary conditions

The boundary conditions for uDALES are specified under the &BC header in namoptions.###.

Momentum

Top

Determined by BCtopm. Possible values:

  • 1: free-slip, i.e. zero flux.
  • 2: no-slip, i.e. zero velocity.
  • 3: variable vertical velocity (necessary with inflow-outflow lateral boundary conditions).

Bottom

NB: only relevant if the bottom of the domain is not covered by floor facets. Determined by BCbotm. Possible values:

  • 1: free slip, i.e. zero flux.
  • 2: flux given by wall function involving temperature.
  • 3: flux given by neutral wall function.

Walls

Determined by iwallmom. Possible values:

  • 1: free-slip, i.e. zero flux.
  • 2: flux given by wall function involving temperature.
  • 3: flux given by neutral wall function.

x

Determined by BCxm. Possible values:

  • 1: periodic
  • 2: inflow-outflow, fixed profile
  • 3: inflow-outflow, inflow given by time-varying profile from precursor simulation

y

Determined by BCym. Possible values:

  • 1: periodic
  • 2: inflow-outflow, fixed profile

Temperature

Only required when ltempeq = .true.

Top

Determined by BCtopT. Possible values:

  • 1: constant flux given by wttop.
  • 2: constant temperature given by thl_top.

Bottom

Determined by BCbotT. Possible values:

  • 1: constant flux given by wtsurf.
  • 2: flux given by wall function. Temperature of ghost cells below floor facets given by thls.

Walls

Determined by iwalltemp. Possible values:

  • 1: constant flux given by bctfxm/bctfxp for facets with normal in -/+ x-direction, bctfym/bctfyp for facets with normal in -/+ y-direction, and bctfz for facets with normal in +z direction.
  • 2: flux given by wall function.

Moisture

Determined by iwallmoist. Possible values:

  • 1: constant flux given by bcqfxm/bcqfxp for facets with normal in -/+ x-direction, bcqfym/bctfyp for facets with normal in -/+ y-direction, and bcqfz for facets with normal in +z direction.
  • 2: flux given by wall function.

Scalars

Only relevant when nsv > 0.

Top

Determined by BCtops. Possible values:

  • 1: constant flux given by wsvtop.
  • 2: constant value given by sv_top.

Bottom

NB: only relevant if the bottom of the domain is not covered by floor facets. Determined by BCbots. Possible values:

  • 1: zero flux.

x

Determined by BCxs. Possible values:

  • 1: periodic
  • 2: inflow-outflow, fixed profile
  • 3: inflow-outflow, inflow given by time-varying profile from precursor simulation
  • 4: inflow-outflow, fixed profile imposed only in a narrow strip around the domain's central y-plane; used for demonstration/testing purposes rather than production use.

y

Determined by BCys. Possible values:

  • 1: periodic
  • 2: inflow-outflow, fixed profile