{"id":295681,"date":"2023-07-31T14:45:14","date_gmt":"2023-07-31T14:45:14","guid":{"rendered":"\/forum\/forums\/topic\/time-step-determination-for-les-based-case\/"},"modified":"2023-07-31T14:45:14","modified_gmt":"2023-07-31T14:45:14","slug":"time-step-determination-for-les-based-case","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/time-step-determination-for-les-based-case\/","title":{"rendered":"Time-step determination for LES based case"},"content":{"rendered":"

Hi everyone,<\/p>\n

I have some doubts regarding time step calculations and i am using CFL = (u * Δ<\/span>t\/Δ<\/span>x)<\/strong> formular. I use CFL <\/strong>number as 1<\/em> , for u <\/strong>i am using 383.9 m\/s<\/em> but Δ<\/span>x<\/strong> is what confusing me. According to some resources Δ<\/span>x<\/strong> represent the meaning of ,characteristic length<\/span>, x direction cell length<\/span>, minimum grid size<\/span>, and cell length<\/span>. So I don’t know what definition to choose in this case.<\/p>\n

My Δ<\/span>x<\/strong>, Δ<\/span>y<\/strong>, and Δ<\/span>z<\/strong> mesh sizes around my blade (wall) are below,<\/p>\n

\u2206Y<\/strong>           <\/span>1.66E-06m (Y+ = 1<\/em>)<\/p>\n

\u2206X<\/strong>           <\/span>1.99E-04m (X+ = 120<\/em>)<\/p>\n

\u2206Z<\/strong>           <\/span>4.98E-05m (Z+ = 30<\/em>)<\/p>\n

So, what value should i use for my time-step calculations ?<\/p>\n

Also, i have seen some people are using cube root method as well, can someone explain this method as well, and are there any other methods that ANSYS has recommended to calculate time-step ?<\/p>\n

 <\/p>\n

Highly appreciate for the guidance.<\/p>\n","protected":false},"template":"","class_list":["post-295681","topic","type-topic","status-closed","hentry"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t