{"id":196164,"date":"2021-10-29T13:41:18","date_gmt":"2021-10-29T13:41:18","guid":{"rendered":"\/forum\/forums\/reply\/196164\/"},"modified":"2021-10-29T13:41:18","modified_gmt":"2021-10-29T13:41:18","slug":"196164","status":"publish","type":"reply","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/196164\/","title":{"rendered":"Reply To: For analysis of flow over cylinder or sphere in 2D- How does ANSYS knows it&#8217;s sphere or cylinder."},"content":{"rendered":"<p><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/forum-uploads\/956\/EF7E9JPEAFHJ.png\" width=\"411\" height=\"233\" \/>Let me explain what I did with a 2D circle for Lumped Heat Analysis. I created a circle (assuming the cross-section of the sphere will be a circle). This circle I assumed as made of silver. So from the Biot formula (Bi = 0.05- assumed), I found the value of heat transfer coefficient (h)- in this case, many web resources used R as characteristic length (Lc) but according to the conventional formula, it should be Volume\/Surface Area. <strong>Question 1: Why Lc has been chosen as R instead of R\/3. <\/strong><br \/>\nAfter meshing and named selections, in fluent I set the outer wall as constant temperature with convective heat transfer coefficient as obtained from Biot formula and solved the system. <strong>Question 2: I found that the obtained value from ANSYS doesn&#8217;t match with either case of cylinder or sphere analytical formula (attached image).<\/strong> But once I did a 3D analysis of the sphere, I got the correct answer- matching with analytical results.<br \/>\nSo, <strong>Doubt came to my mind: how will ANSYS determine sphere and cylinder in 2D. But you answered it and I am satisfied- I will try and let you know the results.<\/strong><br \/>\nIf I need to simulate for flow analysis (assuming the whole circle- considering as sphere- since at Re = 200 or so, we get vortices so I assume it better to go with full circle), but based on my past experience I found that coefficient of lift and drag doesn&#8217;t match with lift force and drag force- as they are linked by analytical formula. <strong>Question 3: Will I get an answer if I calculate the lift and drag coefficient from the lift and drag forces, <\/strong>because I know it must be sphere- so the surface area constricts the flow. <i>Is this a good alternative? <\/i><\/p>\n","protected":false},"template":"","class_list":["post-196164","reply","type-reply","status-publish","hentry"],"aioseo_notices":[],"aioseo_head":"\n\t\t<!-- All in One SEO 4.9.10 - aioseo.com -->\n\t<meta name=\"description\" content=\"Let me explain what I did with a 2D circle for Lumped Heat Analysis. I created a circle (assuming the cross-section of the sphere will be a circle). This circle I assumed as made of silver. So from the Biot formula (Bi = 0.05- assumed), I found the value of heat transfer coefficient (h)- in\" \/>\n\t<meta name=\"robots\" content=\"max-image-preview:large\" \/>\n\t<link rel=\"canonical\" href=\"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/196164\/\" \/>\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 Learning Forum | Ansys Innovation Space\" \/>\n\t\t<meta property=\"og:type\" content=\"article\" \/>\n\t\t<meta property=\"og:title\" content=\"Reply To: For analysis of flow over cylinder or sphere in 2D- How does ANSYS knows it\u2019s sphere or cylinder. | Ansys Learning Forum\" \/>\n\t\t<meta property=\"og:description\" content=\"Let me explain what I did with a 2D circle for Lumped Heat Analysis. I created a circle (assuming the cross-section of the sphere will be a circle). This circle I assumed as made of silver. So from the Biot formula (Bi = 0.05- assumed), I found the value of heat transfer coefficient (h)- in\" \/>\n\t\t<meta property=\"og:url\" content=\"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/196164\/\" \/>\n\t\t<meta property=\"og:image\" content=\"https:\/\/innovationspace.ansys.com\/forum\/forum\/wp-content\/uploads\/forum-uploads\/956\/EF7E9JPEAFHJ.png\" \/>\n\t\t<meta property=\"og:image:secure_url\" content=\"https:\/\/innovationspace.ansys.com\/forum\/forum\/wp-content\/uploads\/forum-uploads\/956\/EF7E9JPEAFHJ.png\" \/>\n\t\t<meta property=\"article:published_time\" content=\"2021-10-29T13:41:18+00:00\" \/>\n\t\t<meta property=\"article:modified_time\" content=\"2021-10-29T13:41:18+00:00\" \/>\n\t\t<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n\t\t<meta name=\"twitter:title\" content=\"Reply To: For analysis of flow over cylinder or sphere in 2D- How does ANSYS knows it\u2019s sphere or cylinder. | Ansys Learning Forum\" \/>\n\t\t<meta name=\"twitter:description\" content=\"Let me explain what I did with a 2D circle for Lumped Heat Analysis. I created a circle (assuming the cross-section of the sphere will be a circle). This circle I assumed as made of silver. So from the Biot formula (Bi = 0.05- assumed), I found the value of heat transfer coefficient (h)- in\" \/>\n\t\t<meta name=\"twitter:image\" content=\"https:\/\/innovationspace.ansys.com\/forum\/forum\/wp-content\/uploads\/forum-uploads\/956\/EF7E9JPEAFHJ.png\" \/>\n\t\t<script type=\"application\/ld+json\" class=\"aioseo-schema\">\n\t\t\t{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/forums\\\/reply\\\/196164\\\/#breadcrumblist\",\"itemListElement\":[{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum#listItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\",\"nextItem\":{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/forums\\\/reply\\\/196164\\\/#listItem\",\"name\":\"Reply To: For analysis of flow over cylinder or sphere in 2D- How does ANSYS knows it&#8217;s sphere or cylinder.\"}},{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/forums\\\/reply\\\/196164\\\/#listItem\",\"position\":2,\"name\":\"Reply To: For analysis of flow over cylinder or sphere in 2D- How does ANSYS knows it&#8217;s sphere or cylinder.\",\"previousItem\":{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum#listItem\",\"name\":\"Home\"}}]},{\"@type\":\"Organization\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/#organization\",\"name\":\"Ansys Learning Forum\",\"description\":\"Ansys Innovation Space\",\"url\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/\"},{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/forums\\\/reply\\\/196164\\\/#webpage\",\"url\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/forums\\\/reply\\\/196164\\\/\",\"name\":\"Reply To: For analysis of flow over cylinder or sphere in 2D- How does ANSYS knows it\\u2019s sphere or cylinder. | Ansys Learning Forum\",\"description\":\"Let me explain what I did with a 2D circle for Lumped Heat Analysis. 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