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® 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:

• The range of temperatures in a model is between 100°F and 1200°F.
• = 0.3.
• = 0.8.

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