{"id":157234,"date":"2022-06-06T08:33:13","date_gmt":"2022-06-06T08:33:13","guid":{"rendered":"\/knowledge\/forums\/topic\/with-same-boundary-conditions-why-gray-and-non-gray-do-models-are-showing-different-results-2\/"},"modified":"2022-06-06T08:33:13","modified_gmt":"2022-06-06T08:33:13","slug":"with-same-boundary-conditions-why-gray-and-non-gray-do-models-are-showing-different-results-2","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/with-same-boundary-conditions-why-gray-and-non-gray-do-models-are-showing-different-results-2\/","title":{"rendered":"With same boundary conditions, why gray and non-gray DO models are showing different results?"},"content":{"rendered":"<p>The non-gray DO model specifies that BOTH radiation absorption and emission occur at different wavelength bands. These bands are specified in the non-gray DO model settings. In the wall boundary condition, instead of the wall Internal Emissivity being under the Thermal tab, it is now under the Radiation tab.  Since wall emission of radiation also occurs at the wavelength bands set out in the model, there is now one emissivity for each band.  The default value of these band emissivities is always 1.0.  This is not a bug: band emissivity will generally differ from spectrum average emissivity. However, since the overall Internal Emissivity for the two setups is different, thermal results will differ.<\/p>\n","protected":false},"template":"","class_list":["post-157234","topic","type-topic","status-publish","hentry","topic-tag-ansys-fluent","topic-tag-radiation"],"aioseo_notices":[],"aioseo_head":"\n\t\t<!-- All in One SEO 4.9.10 - aioseo.com -->\n\t<meta name=\"description\" content=\"The non-gray DO model specifies that BOTH radiation absorption and emission occur at different wavelength bands. These bands are specified in the non-gray DO model settings. In the wall boundary condition, instead of the wall Internal Emissivity being under the Thermal tab, it is now under the Radiation tab. Since wall emission of radiation also\" \/>\n\t<meta name=\"robots\" content=\"max-image-preview:large\" \/>\n\t<link rel=\"canonical\" href=\"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/with-same-boundary-conditions-why-gray-and-non-gray-do-models-are-showing-different-results-2\/\" \/>\n\t<meta name=\"generator\" content=\"All in One SEO (AIOSEO) 4.9.10\" \/>\n\t\t<meta property=\"og:locale\" content=\"en_US\" \/>\n\t\t<meta property=\"og:site_name\" content=\"Ansys Knowledge | Ansys Innovation Space\" \/>\n\t\t<meta property=\"og:type\" content=\"article\" \/>\n\t\t<meta property=\"og:title\" content=\"With same boundary conditions, why gray and non-gray DO models are showing different results? | Ansys Knowledge\" \/>\n\t\t<meta property=\"og:description\" content=\"The non-gray DO model specifies that BOTH radiation absorption and emission occur at different wavelength bands. These bands are specified in the non-gray DO model settings. In the wall boundary condition, instead of the wall Internal Emissivity being under the Thermal tab, it is now under the Radiation tab. Since wall emission of radiation also\" \/>\n\t\t<meta property=\"og:url\" content=\"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/with-same-boundary-conditions-why-gray-and-non-gray-do-models-are-showing-different-results-2\/\" \/>\n\t\t<meta property=\"article:published_time\" content=\"2022-06-06T08:33:13+00:00\" \/>\n\t\t<meta property=\"article:modified_time\" content=\"2022-06-06T08:33:13+00:00\" \/>\n\t\t<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n\t\t<meta name=\"twitter:title\" content=\"With same boundary conditions, why gray and non-gray DO models are showing different results? | Ansys Knowledge\" \/>\n\t\t<meta name=\"twitter:description\" content=\"The non-gray DO model specifies that BOTH radiation absorption and emission occur at different wavelength bands. These bands are specified in the non-gray DO model settings. In the wall boundary condition, instead of the wall Internal Emissivity being under the Thermal tab, it is now under the Radiation tab. 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