The Solar Loads Model
The Solar Loads model is used to model radiation loads from the sun — both direct and diffuse. This optional model is available with Surface-to-Surface Radiation and works with either the Gray or Multiband spectrum models.
The solar emissions are considered together with terrestrial emissions within the context of a given spectrum model. For the Gray spectrum model, the total solar loads are applied to the single transfer system representing the full-thermal spectrum. For the Multiband spectrum model, the solar loads are divided between spectral bands that are based on Planck’s distribution for a blackbody at the effective surface temperature of the sun. These per-band solar emissions are then subject to the radiation surface properties for the associated band as are all other per-band emissions.
When the Solar Loads model is selected for a continuum, a Solar Loads node becomes visible under the Models node for that continuum.
Some changes to input parameters of the solar load specification method can result in a change in solar direction and fluxes. When this change happens, solar load distribution on patches is immediately recalculated.
| Note | Each continuum using the Surface-to-Surface Radiation model can also use the Solar Loads model. However, if one such continuum uses Solar Loads, all such continua must use it, and the settings for Solar Loads in each continuum must be the same. If this condition is not met, Simcenter STAR-CCM+ displays an error message at run time. |
| Theory | See Theory Guide—Solar Radiation. | ||
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| Properties | Key properties are: Coordinate System, Solar Specification Option. See Solar Load Model Properties. | ||
| Activates | Model Controls (child nodes) | Manual Specification | |
| Field Functions | Direct Solar Incident Radiation, Direct Solar Incident Radiation of <band-name>, Diffuse Solar Irradiation, Diffuse Solar Irradiation on External Side, Direct Solar Irradiation, Direct Solar Irradiation on External Side. See Radiation Field Functions Reference. | ||
Solar Loads Model Properties
- Coordinate System
- Specifies the coordinate system (laboratory by default). The drop-down list of this property includes any local coordinate systems that exist in the simulation.
- Solar Specification Option
- Selects the method for specifying solar values.
- Manual specification
- Activates the Manual Specification sub-node, in which you can specify directions and fluxes.
- Solar calculator
- Activates the Solar Calculator sub-node, in which you can specify values such as date, time and geographical locations, and obtain calculations of directions and fluxes.
The solar emissions are subject to the radiative surface properties (see Radiation Properties on Boundaries) specified with the use of either the Gray or the Multiband Thermal Radiation models. No additional radiation property specification on boundaries is needed when the Solar Loads model is enabled.
Manual Specification
The Solar Loads model is fully closed by defining the following properties of the Manual Specification node: the sun direction vector in a specified coordinate system, the direct solar flux, and the diffuse solar flux. The properties can also be defined with field function syntax. For example, you can define the orientation of the sun as a function of time by defining the Azimuth and Altitude properties with expressions such as sin(100*$Time).
If the definitions of the angles and/or the direct solar flux are a function of time, the solar loads are recalculated automatically during each time-step.
- Manual Specification Properties
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- Azimuth
- Sets the sun direction vector horizontal component.
- Altitude
- Sets the sun direction vector vertical or elevation component.
- Direct Solar Flux
- Sets the solar radiative energy directly from the sun along the specified direction vector.
- Diffuse Solar Flux
- Sets the solar radiative energy from the surrounding environment.