Learning Forum

[apaul]

Greetings!

I am facing an issue when simulating a rotating fluid body within a fluid channel body. Here is a description of the situation and problem; along with an attached image and my questions.

Situation:

A 3D, Transient simulation involving 2 bodies was setup in FLUENT, as shown in attached image.

In 'DesignModeler', a 3D bluff body was drawn. A sphere 'enclosure' was made around the bluff body, and the bluff body was removed (deleted/suppressed). Then, a box 'enclosure' was made around this sphere. Both bodies were set to 'Fluid' condition. In 'Meshing', the default meshing conditions was taken; and mesh generated.

In Setup, 'Transient' mode was selected. 'Air' is the material given. In 'Setup>Cell Zone Conditions', the sphere was made rotating with 'mesh motion' selected, with a rotational speed of 2 rad/s. In 'Boundary Conditions', inlet velocity was given as 25 m/s. Outer walls was given a specified shear value of 0 units. Outlet is 'pressure outlet'. The inner walls of the bluff body shape is made 'rotating wall' with no rotational velocity specified.

In 'Solution' section, 'initialisation' was done & simulation done for a time step of 0.001 second, for 1000 time steps, and 6 iterations/time step.

Problem:

A separate 'Results' component was pulled in, and the '.cdat' results loaded. I created a plane along XY axis, and plotted the contour of "Velocity in Stn Frame'. The result is shown in the attached image. A gap occurs in the flow domain, which is unintended.

Questions:

• Could you tell me why it occurs? 


• Will the simulation be accurate, even if I get that gap?


• Any way to close that gap? Or, how to prevent it from occuring?

 

If you can help me, please help me. Should you need additional info, please reply. Thanks in advance, for your time and help.

• Regards,


• A Paul


• (Post graduate student, Aerospace Engg)

#EDIT_IN_ORIGINAL_POST

Picture:

[Rob]

Please post the images into the thread: as staff we're not permitted to open/download attachments. 

[apaul]

Hi! Thanks for your reply. I have attached the image below.

 

 

[Rob]

Thanks. Check the centre of rotation: there looks to be a slight overlap in the contour at 12 o'clock and 3 o'clock (it's visible there anyway) so I suspect you got the axis definition wrong. 

[apaul]

Hi!

Thanks for your reply. I checked the axis definitions and found a mistake, as the rotational axis didn't match with axis of the body. After fixing the error, the gaps in contours disappeared. I have attached the final result obtained after correction.

Thank you very much! Best regards!