# SOLAR_RADIATION_MODEL

Specifies a solar radiation model.

## Type

AcuSolve Command

## Syntax

SOLAR_RADIATION_MODEL("name") {parameters...}

## Qualifier

User-given name.

- specular_transmissivity_type (enumerated) [=constant]
- Type of the specular transmissivity.
- constant or const
- Constant specular transmissivity. Requires specular_transmissivity.
- piecewise_linear or linear
- Piecewise linear curve fit. Requires specular_transmissivity_curve_fit_values and specular_transmissivity_curve_fit_variable.
- cubic_spline or spline
- Cubic spline curve fit. Requires specular_transmissivity_curve_fit_values and specular_transmissivity_curve_fit_variable.

- specular_transmissivity (enumerated) >=0 <=1 [=0]
- Constant value of the specular transmissivity. Used with constant specular transmissivity type.
- specular_transmissivity_curve_fit_values (array) [={0,0;90,0}]
- A two-column array of independent-variable/emissivity data values. Used with piecewise_linear and cubic_spline specular transmissivity types.
- specular_transmissivity_curve_fit_variable (enumerated) [=incidence_angle]
- Independent variable of the curve fit. Used with piecewise_linear and
cubic_spline specular transmissivity types.
- incidence_angle or incident_angle or angle
- Incidence angle with respect to the surface.

- diffuse_transmissivity_type (enumerated) [=constant]
- Type of the diffuse transmissivity.
- constant or const
- Constant diffuse transmissivity. Requires diffuse_transmissivity.
- piecewise_linear or linear
- Piecewise linear curve fit. Requires diffuse_transmissivity_curve_fit_values and diffuse_transmissivity_curve_fit_variable.
- cubic_spline or spline
- Cubic spline curve fit. Requires diffuse_transmissivity_curve_fit_values and diffuse_transmissivity_curve_fit_variable.

- diffuse_transmissivity (enumerated) >=0 <=1 [=0]
- Constant value of the diffuse transmissivity. Used with constant diffuse transmissivity type.
- diffuse_transmissivity_curve_fit_values (array) [={0,0;90,0}]
- A two-column array of independent-variable/emissivity data values. Used with piecewise_linear and cubic_spline diffuse transmissivity types.
- diffuse_transmissivity_curve_fit_variable (enumerated) [=incidence_angle]
- Independent variable of the curve fit. Used with piecewise_linear and
cubic_spline diffuse transmissivity types.
- incidence_angle or incident_angle or angle
- Incidence angle with respect to the surface.

- specular_reflectivity_type (enumerated) [=constant]
- Type of the specular reflectivity.
- constant or const
- Constant specular reflectivity. Requires specular_reflectivity.
- piecewise_linear or linear
- Piecewise linear curve fit. Requires specular_reflectivity_curve_fit_values and specular_reflectivity_curve_fit_variable.
- cubic_spline or spline
- Cubic spline curve fit. Requires specular_reflectivity_curve_fit_values and specular_reflectivity_curve_fit_variable.

- specular_reflectivity (enumerated) >=0 <=1 [=0]
- Constant value of the specular reflectivity. Used with constant specular reflectivity type.
- specular_reflectivity_curve_fit_values (array) [={0,0;90,0}]
- A two-column array of independent-variable/emissivity data values. Used with piecewise_linear and cubic_spline specular reflectivity types.
- specular_reflectivity_curve_fit_variable (enumerated) [=incidence_angle]
- Independent variable of the curve fit. Used with piecewise_linear and
cubic_spline specular reflectivity types.
- incidence_angle or incident_angle or angle
- Incidence angle with respect to the surface.

- diffuse_reflectivity_type (enumerated) [=constant]
- Type of the diffuse reflectivity.
- constant or const
- Constant diffuse reflectivity. Requires diffuse_reflectivity.
- piecewise_linear or linear
- Piecewise linear curve fit. Requires diffuse_reflectivity_curve_fit_values and diffuse_reflectivity_curve_fit_variable.
- cubic_spline or spline
- Cubic spline curve fit. Requires diffuse_reflectivity_curve_fit_values and diffuse_reflectivity_curve_fit_variable.

- diffuse_reflectivity (enumerated) >=0 <=1 [=0]
- Constant value of the diffuse reflectivity. Used with constant diffuse reflectivity type.
- diffuse_reflectivity_curve_fit_values (array) [={0,0;90,0}]
- A two-column array of independent-variable/emissivity data values. Used with piecewise_linear and cubic_spline diffuse reflectivity types.
- diffuse_reflectivity_curve_fit_variable (enumerated) [=incidence_angle]
- Independent variable of the curve fit. Used with piecewise_linear and
cubic_spline diffuse reflectivity types.
- incidence_angle or incident_angle or angle
- Incidence angle with respect to the surface.

## Description

This command specifies an ideal grey-surface solar radiation model to calculate the solar heat flux. This model is only applicable to solar radiation surfaces, and is not used for the radiation_heat_flux variable in the ELEMENT_BOUNDARY_CONDITION command or for radiation surfaces. Four material properties of the surface are specified here: specular transmissivity, diffuse transmissivity, specular reflectivity, and diffuse reflectivity. The surface absorptivity is defined to be one minus the sum of these four. See the SOLAR_RADIATION command for further details.

```
SOLAR_RADIATION_MODEL( "my solar radiation model" ) {
specular_transmissivity_type = constant
specular_transmissivity = 0.2
diffuse_transmissivity_type = constant
diffuse_transmissivity = 0.15
specular_reflectivity_type = constant
specular_reflectivity = 0.1
diffuse_reflectivity_type = constant
diffuse_reflectivity = 0.05
}
SOLAR_RADIATION_SURFACE( "hot wall" ) {
solar_radiation_mdoel = "my solar radiation model"
...
}
```

```
SOLAR_RADIATION_MODEL( "curve fit specular transmissivity model" ) {
specular_transmissivity_type = piecewise_linear
specular_transmissivity_curve_fit_values = { 0, 0 ;30, 0 ;90, 0.2 }
specular_transmissivity_curve_fit_variable = incidence_angle
...
}
```

reduces the specular transmissivity from 0.2 at normal (90 degree) incidence to zero for incidence angles less than 30 degrees. In general, the problem must contain the variable defined by curve fit variable parameter; this is not an issue here since the incidence angle is always available. Each of the curve fit values parameters is a two-column array corresponding to the independent variable and the surface property values. The independent variable values must be in ascending order. The limit point values of the curve fit are used when the curve fit variable falls outside of the curve fit limits.

```
0 0
30 0
90 0.2
```

```
SOLAR_RADIATION_MODEL( "curve fit specular transmissivity model" ) {
specular_transmissivity_type = piecewise_linear
specular_transmissivity_curve_fit_values = Read( "spec_trans.fit" )
specular_transmissivity_curve_fit_variable = incidence_angle
...
}
```