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ravindersingh December 11, 2011 23:30

Mesh rotation due to flow field

I am simulating unsteady flow over 2d wind turbine. I want the turbine to start rotating due to flow field.

For this I am writing a UDF using the macro DEFINE_CG_MOTION which will rotate the domain containing the blade.

I am following the example given in the UDF manual. But in my UDF I want to calculate the rotational velocity from the moment.

From the forums I came to know about the command "Compute_Force_and_Moment", however I have no idea how to use it and also didn't find much information from internet. Also I get Cm curve from the menu Solve->Monitor->Forces. How can I use it within the UDF?

Please help. Also advide if there is an alternate method available.

tapanshah001 September 11, 2012 03:21

Facing the same problem
hey...i am trying to do similar thing.....please help me out if you have found a answer...

Hypersonicflow September 11, 2012 08:42


I have some UDF that calculate forces and moments at each time step. Send me your email adress than I could send them to you.:)

samidabest September 11, 2012 13:54


I am trying to make a simple heat exchanger in my 2d rectangle shaped pipe flow model. Since heat exchangers aren't what I'm focusing on in this project, I'd like to implement a very simple heat exchanger model in a specified zone. Basically one where I can tell it what the 'auxiliary' temp. is, and what effectiveness it has for a given primary fluid temp and let fluent work out the rest.

My model is basically a 2d rectangle with simple zones. It doesn't have heat exchanger pipes or tubes going though any region

When I turn on the Heat exchanger model in fluent, I see the three options ( dual cell, ungrouped macro, and macro model group) but the bottom two are greyed out leaving only "Dual Cell Model" available to select.. I tried going though this but it seems to be a lot more elaborate than my model and requires actually making another zone for the auxiliary cooling/heating fluid.

Can someone please give me some advice on Fluents heat exchanger models and why the other two options (ungrouped macro and macro) are not available.

Please, Please, Please! help, On a project and the dead line is approaching, if any of this is unclear please let me know and I'll try to describe it better.

Dorit October 13, 2012 05:36

Hi tapanshah001 and ravindersingh,

I'm also trying to model a wind turbines rotational speed based on the moment that it generates. I've also come across the DEFINE_CG_MOTION macro but I haven't quite figured how to use it. Did you get anywhere?

I tried to use the macro with some dummy values but it just won't update my rotational speed. It always uses 0.1 rather than increasing it. I'm using this equation inside the macro to update the rotational speed around the Y axis:


Do you know how it should be written?


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