23.3. How-To

NEF materials are applied via the DIRSIG materials database (.mat) and are specified using the DIRSIG4 format. The following example shows a NEF material file being used to compute the reflectance. In the example, THERM is being used to predict the surface temperatures.

MATERIAL_ENTRY {
    NAME = asphalt
    ID = 1

    SURFACE_PROPERTIES {
        REFLECTANCE_PROP_NAME = NEFBeardMaxwell
        REFLECTANCE_PROP {
            NEF_MAT_FILE = /home/NEFDS/dbmF_05-1/Materials/Single_Materials/0693UUUASP.nmf
        }
    }

    RAD_SOLVER_NAME = Generic
    RAD_SOLVER {
        INITIAL_SAMPLE_COUNT = 25
        MAX_BOUNCES = 2
        SAMPLE_DECAY_RATE = 10
    }

    TEMP_SOLVER_NAME = Therm
    TEMP_SOLVER {
        SPECIFIC_HEAT = 0.4650
        THERMAL_CONDUCTIVITY = 20.9300
        MASS_DENSITY = 1.0000
        SPECULARITY = 0.10
        VISIBLE_EMISSIVITY = 0.95
        THERMAL_EMISSIVITY = 0.65
        EXPOSED_AREA = 0.40
    }
}

Note that some NEF material files actually come with much of the information needed by THERM. This includes thermal conductivity, specific heat, and mass density. DIRSIG does not automatically parse this information in to a thermal model at this time. However, this information can still be manually added by the user if desired. The NEF User's Guide details the file format of the materials files and explains where this information can be found.