{"id":394254,"date":"2024-11-19T11:16:59","date_gmt":"2024-11-19T11:16:59","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/incorrect-velocity-streamlines-and-observed-velocities-profile\/"},"modified":"2024-11-19T11:16:59","modified_gmt":"2024-11-19T11:16:59","slug":"incorrect-velocity-streamlines-and-observed-velocities-profile","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/incorrect-velocity-streamlines-and-observed-velocities-profile\/","title":{"rendered":"Incorrect velocity streamlines and observed velocities profile"},"content":{"rendered":"

<p>Hello everyone. I’m conducting an MRF simulation of a ceiling fan in a room. The domain(Please check image-1) is set up in a way that there is an outer chamber, inner chamber, a rotating domain(cylinder) which contains the fan. We follow this domain setup based on the directions of the Board of Indian Standards. \"\"<\/p><p>Based on widely used methodolgy, I have given 3 booleans:<\/p><p>1) Outer chamber subtracted from inner chamber, preserve tools ‘no’ and hence the inner chamber becomes walls<\/p><p>2) Subtract the MRF cylinder disk from the outer chamber, preserve tool bodies ‘yes’.<\/p><p>3) Subtract the fan from the rotating disk, preserve tool bodies ‘no’, the fan becomes wall.<\/p><p>Thus I have only two bodies now, one outer chamber and one cylinder disk. I select them both and make it a single part to ensure conformal mesh interface between both.<\/p><p>The mesh is of very fine nature with very acceptable orthogonal(>0.01) and skewness values(<0.95). I then create named selection and select the fan(hub included) faces and describe them as walls.<\/p><p><\/p><p>In setup phase, I select steady state then SA turbulence model, then cell zone is set up like this:<\/p><p>\"\"<\/p><p>I’ve set up the coordinates of axis of rotation properly.<\/p><p>\"\"<\/p><p>In boundary conditions I have set the fan to moving wall with 0 rpm. The coordinates of axis of rotation of fan are same as that of cylinder. <\/p><p><\/p><p>\"\"I then set up the interface properly.<\/p><p>Then I use simple method with second order upwind.<\/p><p>Then I set up report definitions for fields of interest. Lift, drag, velocity average on a plane above the rotating disk and then a plane 1.5m below the disk to ensure global convergence is reached.<\/p><p>I then run the simulation and after my scaled residuals and variables of interest have converged. I extract the solution.<\/p><p>Now, If i were to plot axial velocity on a line 1.5m below the fan, from the hub to root it would appear something like the plot below(red line). The plot also shows our curve(blue line):<\/p><p><\/p><p>The red line curve is for a fan in the market. I DONT expect similar values as the operating conditions have changed. But i do expect similar behaviour i.e. like a bell curve. Every ceiling fan research paper has similar curve. Now, our new design is elliptical, has a winglet and has aifoils with changing Angles of attack over the blade but would that affect this curve? or is the simulation incorrect somewhere?<\/p><p>I have tried to eliminate every possible error, refined the mesh, tried the sliding mesh with non conformal, reduced time step size, simpled and coupled solver but to no avail. Im left helpless right now.<\/p><p>I have been investing days and nights into this since May and extreme amount of efforts have gone into this. I have a lot at stake as they want to 3D print our model for experimental investigation and I can’t afford to get vague values.<\/p><p>Kindly help me. I’ll provide you with whatever information you deem as necessary.<\/p><\/p>\n","protected":false},"template":"","class_list":["post-394254","topic","type-topic","status-publish","hentry","topic-tag-boolean","topic-tag-boundary-conditions","topic-tag-mrf","topic-tag-mrf-frozen-rotor","topic-tag-sliding-mesh","topic-tag-steady-state","topic-tag-transient","topic-tag-velocity-contours-1"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_subscription":["482699","199"],"_bbp_author_ip":["103.120.31.122"],"_btv_view_count":["226"],"_bbp_topic_status":["unanswered"],"_bbp_notification_enabled":["482699"],"_bbp_topic_id":["394254"],"_bbp_forum_id":["27792"],"_bbp_engagement":["199","482699"],"_bbp_voice_count":["2"],"_bbp_reply_count":["12"],"_bbp_last_reply_id":["394499"],"_bbp_last_active_id":["394499"],"_bbp_last_active_time":["2024-11-20 11:45:42"]},"test":"msm19b039iiitdm-ac-in"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/394254","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\/394254\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=394254"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}