{"id":45466,"date":"2020-06-25T09:18:52","date_gmt":"2020-06-25T09:18:52","guid":{"rendered":"\/forum\/forums\/topic\/choosing-a-real-gas-model\/"},"modified":"2020-06-25T09:18:52","modified_gmt":"2020-06-25T09:18:52","slug":"choosing-a-real-gas-model","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/choosing-a-real-gas-model\/","title":{"rendered":"Choosing a Real Gas Model"},"content":{"rendered":"

Hello,<\/p>\n

<\/p>\n

for my thesis I am currently calculating\/deciding whether I need to implement a real gas model or if it’s sufficient whether I use the ideal gas law.<\/p>\n

<\/p>\n

Case 1:<\/p>\n

<\/p>\n

h=30km, Ma=8<\/p>\n

<\/p>\n

p= 1,197kPa, p_t=1,16e7 Pa<\/p>\n

<\/p>\n

T= 226,5K, T_t=3125,7 K<\/p>\n

<\/p>\n

 <\/p>\n

<\/p>\n

Case 2:<\/p>\n

<\/p>\n

h=50 km, Ma=12<\/p>\n

<\/p>\n

p=79,77 Pa, p_t=1,15e7 Pa<\/p>\n

<\/p>\n

T=270,6K, T_t=3734,28 K<\/p>\n

<\/p>\n

 <\/p>\n

<\/p>\n

Now in the Fluent User Guide I discovered the two terms in which the ideal gas model can be used.<\/p>\n

<\/p>\n

p\/p_c<<1<\/p>\n

<\/p>\n

 <\/p>\n

<\/p>\n

or<\/p>\n

<\/p>\n

 <\/p>\n

<\/p>\n

T\/T_c>2 and p\/p_c<1<\/p>\n

<\/p>\n

 <\/p>\n

<\/p>\n

Now my question is which pressure and temperature I should use to determine the required gas model. If I use the ambient (static) pressure (as the “p” in the above equations) I should use the ideal gas law (this was done in similar final papers aswell for Ma=\"8)\". If I use the total pressure I should use a real gas model.<\/p>\n

<\/p>\n

In another final year paper the flow in a height of 80 km with a Ma=23 was simulated. This person used the Redlich-Kwong Real Gas model. My above mentioned calculations\/observations apply to this case aswell which confuses me on which model I should use…<\/p>\n

<\/p>\n

 <\/p>\n

<\/p>\n

Thank you very much in advance for your support.<\/p>\n

<\/p>\n

 <\/p>\n

<\/p>\n

Best regards<\/p>\n

<\/p>\n

 <\/p>\n","protected":false},"template":"","class_list":["post-45466","topic","type-topic","status-closed","hentry"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_old_topic_id":["17647"],"_bbp_old_topic_author_name_id":["Anonymous"],"_bbp_old_is_topic_anonymous_id":["false"],"_bbp_old_closed_status_id":["publish"],"_bbp_author_ip":[null],"_bbp_old_sticky_status_id":["normal"],"_bbp_likes_count":["0"],"_btv_view_count":["2570"],"_bbp_subscription":["250933"],"_bbp_topic_status":["unanswered"],"_bbp_status":["publish"],"_bbp_topic_id":["45466"],"_bbp_forum_id":["27792"],"_bbp_engagement":["22555","176774"],"_bbp_voice_count":["2"],"_bbp_reply_count":["7"],"_bbp_last_reply_id":["118955"],"_bbp_last_active_id":["118955"],"_bbp_last_active_time":["2020-06-25 12:42:46"]},"test":"cfdger"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/45466","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics"}],"about":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/types\/topic"}],"version-history":[{"count":0,"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/45466\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=45466"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}