Spectral Radiation

The radiation model can include the effects of temperature-dependent emissivity. This allows the simulation of the effects of spectral radiation. This variation is in the form of a piece-wise linear table, and is entered on the Material Editor by clicking the Emissivity button, and selecting Piecewise Linear from the Variation Method drop menu.

To account for the spectral characteristics of a surface, use the radiation functions in the following table to construct a second table of total emissivity as a function of temperature to be used in Autodesk Simulation CFD:

0 0 0.0 10,200 5666.7 0.70754
1000 555.6 1.70e-8 10,400 5777.8 0.71806
1200 666.7 7.56e-7 10,600 5888.9 0.72813
1400 777.8 1.06e-5 10,800 6000 0.73777
1600 888.9 7.38e-5 11,000 6111.1 0.74700
1800 1000 3.21e-4 11,200 6222.2 0.75583
2000 1111.1 0.00101 11,400 6333.3 0.76429
2200 1222.2 0.00252 11,600 6444.4 0.77238
2400 1333.3 0.00531 11,800 6555.6 0.78014
2600 1444.4 0.00983 12,000 6666.7 0.78757
2800 1555.6 0.01643 12,200 6777.8 0.79469
3000 1666.7 0.02537 12,400 6888.9 0.80152
3200 1777.8 0.03677 12,600 7000 0.80806
3400 1888.9 0.05059 12,800 7111.1 0.81433
3600 2000 0.06672 13,000 7222.2 0.82035
3800 2111.1 0.08496 13,200 7333.3 0.82612
4000 2222.2 0.10503 13,400 7444.4 0.83166
4200 2333.3 0.12665 13,600 7555.6 0.83698
4400 2444.4 0.14953 13,800 7666.7 0.84209
4600 2555.6 0.17337 14,000 7777.8 0.84699
4800 2666.7 0.19789 14,200 7888.9 0.85171
5000 2777.8 0.22285 14,400 8000 0.85624
5200 2888.9 0.24803 14,600 8111.1 0.86059
5400 3000 0.27322 14,800 8222.2 0.86477
5600 3111.1 0.29825 15,000 8333.3 0.86880
5800 3222.2 0.32300 16,000 8888.9 0.88677
6000 3333.3 0.34734 17,000 9444.4 0.90168
6200 3444.4 0.37118 18,000 10,000 0.91414
6400 3555.6 0.39445 19,000 10,555.6 0.92462
6600 3666.7 0.41708 20,000 11,111.1 0.93349
6800 3777.8 0.43905 21,000 11,666.7 0.94104
7000 3888.9 0.46031 22,000 12,222.2 0.94751
7200 4000 0.48085 23,000 12,777.8 0.95307
7400 4111.1 0.50066 24,000 13,333.3 0.95788
7600 4222.2 0.51974 25,000 13,888.9 0.96207
7800 4333.3 0.53809 26,000 14,444.4 0.96572
8000 4444.4 0.55573 27,000 15,000 0.96892
8200 4555.6 0.57267 28,000 15,555.6 0.97174
8400 4666.7 0.58891 29,000 16,111.1 0.97423
8600 4777.8 0.60449 30,000 16,666.7 0.97644
8800 4888.9 0.61941 40,000 22,222.2 0.98915
9000 5000 0.63371 50,000 27,777.8 0.99414
9200 5111.1 0.64740 60,000 33,333.3 0.99649
9400 5222.2 0.66051 70,000 38,888.9 0.99773
9600 5333.3 0.67305 80,000 44,444.4 0.99845
9800 5444.4 0.68506 90,000 50,000 0.99889
10,000 5555.6 0.69655 100,000 55,555.6 0.99918

Determine the emissivity from the values in this table using the equation:

is the non-dimensional Spectral blackbody emissive power.

is the Spectral Temperature (and units)

is the emittance below 3

is the emittance at longer wavelengths (above 3)

Example:

To determine the Spectral Temperature at 100°F, multiply the wavelength (3) by the temperature in absolute units (560 R). To determine the non-dimensional Spectral blackbody emissive power, use the table above to interpolate the value at the computed spectral tremperature:

1680 9.888e-5

The emissivity at 100°F is:

To determine the Spectral Temperature at 1200°F, multiply the wavelength (3) by the temperature in absolute units (1660 R). To determine the non-dimensional Spectral blackbody emissive power, use the table above to interpolate the value at the computed spectral tremperature:

4980 0.220354

The emissivity at 1200°F is:

Enter the Emissivity and temperature values in a Piecewise Linear property table in the Material Editor:

Emissivity Temperature (F)
0.8 100
0.69 1200
Parent topic: Radiation