Section: ABL

This section is for setting atmospheric boundary layer parameters.

ABL.kappa

type: Real, optional, default = 0.41

Wall model coefficient.

ABL.surface_roughness_z0

type: Real, optional, default = 0.1

Wall model surface roughness length (in meters). When specified, this sets both the aerodynamic (pertaining to velocity) and thermal (pertaining to temperature) roughness lengths. These roughness lengths can be set separately using the two parameters listed below; however, if this parameter (which sets both) is used with either of the roughness parameters below, the code will abort to prevent using conflicting parameters.

ABL.aerodynamic_roughness_length

type: Real, optional, default = 0.1

Wall model surface roughness length (in meters) for aerodynamic processes, i.e., the wall momentum flux/shear stress model.

ABL.thermal_roughness_length

type: Real, optional, default = 0.1

Wall model surface roughness length (in meters) for thermal processes, i.e., the wall temperature flux model.

ABL.normal_direction

type: Integer, optional, default = 2

Wall model normal direction. x-direction = 0, y-direction = 1, z-direction = 2.

ABL.log_law_height

type: Real, optional

Height to evaluate the log law for the wall model. Currently, if this parameter is not specified in the input file, the first half cell height is calculated and is used to set the log law height. Therefore the log law height depends on the domain size and number of elements in the normal direction. If this parameter is set to a number the log law is evaluated at a fixed height. Note: currently the fluctuating velocity terms in the shear stress model are only available at the first cell center above the wall. This limitation will be removed soon.

ABL.surface_temp_flux

type: Real, optional

Surface temperature flux setting for the ABL wall function. Specifies a constant temperature flux at the wall-modeled boundary. This is not a required argument because there are other options for setting up the surface temperature condition.

ABL.surface_temp_timetable

type: String, optional

File name of surface temperature time table, allowing the surface temperature to change with time without specifying a surface temperature rate.

ABL.surface_temp_rate

type: Real, optional

Constant rate at which the surface temperature changes.

ABL.surface_temp_init

type: Real, optional

Initial temperature of the wall-modeled surface. This parameter is only active when the surface temperature rate is specified. If this parameter is active but not specified, the initial temperature will be set to the reference temperature of the simulation.

ABL.surface_temp_rate_tstart

type: Real, optional

Start time of the surface temperature rate of change. Prior to this time, the surface temperature remains at the initial value. This parameter is only active when the surface temperature rate is specified. The default start time is 0.

ABL.temperature_heights

type: List of Reals, mandatory

Height(s) in meters at which temperature values are prescribed.

ABL.temperature_values

type: List of Reals (has to be same length as ABL.temperature_heights), mandatory

Temperature values in Kelvin at the corresponding ABL.temperature_heights. The temperature below the first height is assumed to be constant and equal to the first temperature value. The temperature between values is initialized to have linear variation. The final temperature is constant above the last specified height.

ABL.perturb_velocity

type: Boolean, optional, default = true

If true this flag turns on perturbations to the freestream flow.

ABL.pertub_ref_height

type: Real, optional, default = 50.0

Reference height for velocity perturbations, perturbations exist below this height and decay above this height. Only active when ABL.perturb_velocity = true.

ABL.Uperiods

type: Real, optional, default = 4.0

Number of sinusoidal waves in x-direction. Only active when ABL.perturb_velocity = true.

ABL.Vperiods

type: Real, optional, default = 4.0

Number of sinusoidal waves in y-direction. Only active when ABL.perturb_velocity = true.

ABL.deltaU

type: Real, optional, default = 1.0

Amplitude of fluctuations in x-direction. Only active when ABL.perturb_velocity = true.

ABL.deltaV

type: Real, optional, default = 1.0

Amplitude of fluctuations in y-direction. Only active when ABL.perturb_velocity = true.

ABL.perturb_temperature

type: Boolean, optional, default = false

Perturb temperature field with random fluctuations.

ABL.theta_amplitude

type: Real, optional, default = 0.8 K

Amplitude of the temperature perturbations added to the initial field. Only active when ABL.perturb_temperature is true.

ABL.cutoff_height

type: Real, optional, default = domain height

Height below which temperature perturbations are added

ABL.random_gauss_mean

type: Real, optional, default = 0.0

Mean for the Gaussian random number generator

ABL.random_gauss_var

type: Real, optional, default = 1.0

Variance for the Gaussian random number generator

ABL.bndry_file

type: String, optional, default = “”

NetCDF-4 file name for ABL inflow

ABL.bndry_io_mode

type: Int, optional, default = -1

IO mode (0=output, 1=input)

ABL.bndry_planes

type: String, optional, default = “”

IO planes for ABL inflow

ABL.bndry_output_start_time

type: Real, optional, default = 0.0

Time at which to start ABL inflow output

ABL.bndry_var_names

type: String, optional, default = “”

Variables for IO for ABL inflow

ABL.wall_shear_stress_type

type: String, optional, default = “Moeng”

Wall shear stress model: options include “constant”, “local”, “Schumann”, and “Moeng”

ABL.bndry_output_format

type: String, optional, default = “native”

Output of boundary plane files. Valid values are netcdf and native.

ABL.initial_condition_input_file

type: String, optional, default= “”

File that contains initial conditions for the velocity field in netcdf file format. This file is expected to have the same dimensions as the simulation. Values are passed directly from the file to the velocity field inside the code. Only spanwise velocity components are supported.

ABL.anelastic

type: Boolean, optional, default= false

Activate anelastic behavior. This adds reference_density and reference_pressure fields.

ABL.bottom_reference_pressure

type: Real, optional, default = 1.01325e5

Reference pressure at the bottom of the domain. Used for anelastic ABL.

ABL.initial_wind_profile

type: Boolean, optional, default= false

Activates the reading of wind speed profile from a file. Recommended for RANS models and also for wind conditions input from climate model.

ABL.rans_1dprofile_file

type: String, optional, default = “”

This input is required when the ABL.initial_wind_profile is set to True.

ABL.meso_sponge_start

type: Real, optional, default = 650

Approximate height of the planetary boundary layer height to enable the forcing in the free atmosphere. Recommended for use with RANS model and optionally to run LES with non canonical flow conditions. The method is enabled by default for turbulent kinetic energy. To enable this option for temperature and velocity, the following flags have to be added to the input file.

Temperature.source_terms = TemperatureFreeAtmosphereForcing

ICNS.source_terms = VelocityFreeAtmosphereForcing

ABL.wall_het_model

type: String, optional, default = “none”

Allows the use of different surface model options for the Monin-Obukhov length. Currently supports two options: (i) “none” - original model in the code and (ii) “mol” - Monin-Obukhov length is constant while heat-flux varies

ABL.monin_obukhov_length

type: Real, optional, default = -1e30

Used in conjunction with ABL.wall_het_model. The default value runs a neutral boundary layer.

ABL.terrain_aligned_profile

type: Boolean, optional, default= false

Used in conjunction with immersed forcing for terrain. This option allows the user to align the wind, temperature and turbulence profiles to be aligned with the terrain.