Checking the Center of Gravity

ahmadi · June 11, 2014, 08:42

hi
need some help regarding specifying Center of Gravity of dynamic zone in fluent(rigid body motion)
i use update button in dynamic mesh panel but Value is always zero.

sriny1512 · June 27, 2014, 03:37

Hi ahmadi,
I am doing a CFD analysis of an oil pump using 2.5D re-meshing approach in Ansys 15. The oil pump is of lobe (inner and outer rotor) type. I have the UDF (user defined function) ready where I have defined the RPM of the rotors. In Ansys, in Design modeller, the user can select any body/surface/profile and click on "Tools>Analysis Tools>Mass Properties. This will display the centroid of the selected feature (defined by x, y and z co-ordinates) with respect to global co-ordinate system.

In my case, below is what I did,

1. In Fluent where we define the dynamic mesh zone under "Dynamic mesh"
2. Click on "create/edit" button in "Dynamic mesh zone" window.
3. Select the type as rigid body.
4. In the small selection window (where there is arrow mark to scroll down). Select the appropriate zone defined in UDF (i.e., inner or outer rotor). This selection is made in the "Geometry definition" tab.
5. In the same "Geometry definition", define the centroid by entering the x, y and z values. (I did the same for inner and outer rotors)
6. The contact interface of the rotors fluid volume should be selected as deforming type and is defined by selecting the plane option in the "Geometry definition"tab. In "Meshing options" smoothing and remeshing is ticked.
7. The bottom interface of the rotors fluid volume (non contact one) is defined as per step 6, except that only smoothing option is selected for this.

sriny1512 · June 27, 2014, 04:56

The above method has been used in solving one of the problems. But, I too have a doubt defining x, y and z co-ordinates for dynamic mesh zone. I mean, the method above is correct as it has solved a problem. In another problem, if I use the same method, the rotation of the rotors is not proper when I check in "display zone motion". I guess it is the x, y and z co-ordinates not defined properly is causing the problem.

Anyone, please clearly explain how to define dynamic zones using options available in Fluent.

June 11, 2014, 08:42	Checking the Center of Gravity	#1
ahmadi New Member ahmady.a Join Date: Oct 2013 Posts: 19 Rep Power: 12	hi need some help regarding specifying Center of Gravity of dynamic zone in fluent(rigid body motion) i use update button in dynamic mesh panel but Value is always zero.

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June 27, 2014, 03:37		#2
sriny1512 New Member sreenivas devaraju Join Date: Jun 2014 Posts: 7 Rep Power: 11	Hi ahmadi, I am doing a CFD analysis of an oil pump using 2.5D re-meshing approach in Ansys 15. The oil pump is of lobe (inner and outer rotor) type. I have the UDF (user defined function) ready where I have defined the RPM of the rotors. In Ansys, in Design modeller, the user can select any body/surface/profile and click on "Tools>Analysis Tools>Mass Properties. This will display the centroid of the selected feature (defined by x, y and z co-ordinates) with respect to global co-ordinate system. In my case, below is what I did, 1. In Fluent where we define the dynamic mesh zone under "Dynamic mesh" 2. Click on "create/edit" button in "Dynamic mesh zone" window. 3. Select the type as rigid body. 4. In the small selection window (where there is arrow mark to scroll down). Select the appropriate zone defined in UDF (i.e., inner or outer rotor). This selection is made in the "Geometry definition" tab. 5. In the same "Geometry definition", define the centroid by entering the x, y and z values. (I did the same for inner and outer rotors) 6. The contact interface of the rotors fluid volume should be selected as deforming type and is defined by selecting the plane option in the "Geometry definition"tab. In "Meshing options" smoothing and remeshing is ticked. 7. The bottom interface of the rotors fluid volume (non contact one) is defined as per step 6, except that only smoothing option is selected for this.

June 27, 2014, 04:56		#3
sriny1512 New Member sreenivas devaraju Join Date: Jun 2014 Posts: 7 Rep Power: 11	The above method has been used in solving one of the problems. But, I too have a doubt defining x, y and z co-ordinates for dynamic mesh zone. I mean, the method above is correct as it has solved a problem. In another problem, if I use the same method, the rotation of the rotors is not proper when I check in "display zone motion". I guess it is the x, y and z co-ordinates not defined properly is causing the problem. Anyone, please clearly explain how to define dynamic zones using options available in Fluent.