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Flutter Analysis

Pioneer
Pioneer

Hi,

I am doing flutter anaysis in femap. I am facing problem in putting the values of density. Can anyone please tell me that what density value we should consider in Aerodynamic Factor density function and after this what value of density we should consider for the Aerodynamic physical Data tab(Ref. length and ref. density).

 

and other problem is:

 

When i import mesh from hyermesh or ansys  femap dont read geometry of the model it just read mesh. 

Plz help! thanx in advance.

 

Shery

 

 

 

11 REPLIES

Re: Flutter Analysis

Solution Partner Phenom Solution Partner Phenom
Solution Partner Phenom

Dear Shery,

When you import a mesh from any FEA solver, this is simply mesh: a data collection of grid nodes, elements, material & element properties, loads, constraints, etc.., not geometry. Is the same in FEMAP: when you export a FE model to read in any FEA solver, the output is simply grid nodes, elements, material & elements properties, etc..

If you want to import geometry into FEMAP you need to export the geometry in the other FEM/FEA system using geometry translators like STEP, Parasolid, etc.. and then in FEMAP repeat the process of importing geometry using the same format.

Fortunately, in FEMAP -if required- we can associate geometry & mesh, take a look to command MODIFY > ASSOCIATIVITY > AUTOMATIC, this is a very useful feature if you need to remesh any part of the model, or add loads & constraints based in geometry.

Best regards,
Blas.

 

Blas Molero Hidalgo, Ingeniero Industrial, Director
IBERISA • 48004 BILBAO (SPAIN)
WEB: http://www.iberisa.com
Blog Femap-NX Nastran: http://iberisa.wordpress.com/

Re: Flutter Analysis

Pioneer
Pioneer

Hi BLAS,

 

Thnx for replying. 

i tried your suggestion and i found that we can only use this  fucntion when we have both geometry and mesh if anyone of them is missing then we cant use AUTOMATIC function. In my case geometry is missing when i import mesh with its geometry.

I am using hypermesh for meshing and i am exporting mesh with geometry but still geometry is missing when i import file. Is there any way of importing mesh with its geometry? 

 

Regards

Shery

 

Re: Flutter Analysis

Siemens Phenom Siemens Phenom
Siemens Phenom

Can you export the geometry seperately as one of the supported geometry formats in Femap?  Then you can import that geometry and associate it to the mesh.

Best Regards,
Chip Fricke
Principal Applications Engineer - Femap Product Development

Re: Flutter Analysis

Solution Partner Phenom Solution Partner Phenom
Solution Partner Phenom

Dear Shery,

I told you before, read me again, when you export a nastran (*.dat. *.nas, etc..) mesh from FEM you export grid & nodes, not geometry, this is the same in any FEM pre&postprocesor. If you want to have geometry as well simply export also separately the geometry and later in FEMAP you can import both, in the order you like, first geometry and next mesh, or reverse, it dosen't matter. 

And finally, when both geometry & mesh exist in your FEMAP model, you can associate geometry & mesh using Modify > Associativity > Automatic command. 

This command will attempt to associate the nodes of selected elements with selected solids (Tet or Hex Elements) or surfaces/sheet solids (Shell Elements). In addition to the nodes and elements being associated to the main entity (solids or surfaces/sheet solids), they will then also be associated to the surfaces of solids, curves on those surfaces, and points on those curves allowing you to use geometry based commands in FEMAP (i.e., Loads and Constraints on geometry, any selection method using a geometric entity, etc.), understood?.

Best regards,
Blas.

Blas Molero Hidalgo, Ingeniero Industrial, Director
IBERISA • 48004 BILBAO (SPAIN)
WEB: http://www.iberisa.com
Blog Femap-NX Nastran: http://iberisa.wordpress.com/

Re: Flutter Analysis

Pioneer
Pioneer

Hi BLAS,

thnx for replying.

Yeah , great thanx. Problem solved. 

Thnx again. 

 

Regards 

Shery

Re: Flutter Analysis

Pioneer
Pioneer

Hi Chip Fricke,

thnx for replying. 

yea problem solved. 

 

Regards 

Shery

Re: Flutter Analysis

Pioneer
Pioneer

and can you plz guide me for flutter analysis. I am having problem in defining groups for spline.

How much area should i define in group for spline?  and the area should be the uper skin of wing or it should be the whole wing?

 

Regards

Shery

Re: Flutter Analysis

Solution Partner Experimenter Solution Partner Experimenter
Solution Partner Experimenter

Hi Sherry,

 

My coworker, Ben Names, covered how to set up and run an aeroelastic flutter analysis in this webinar: 

 

https://youtu.be/O8ZGbmLKv8I?t=1602




Aswin John
Marketing Specialist
Structural Design and Analysis

Re: Flutter Analysis

Pioneer
Pioneer

Hi Aswin John,

 

Thnx for relying. 

Yeah i  saw this tutorial many times but i want to know how he set his process up before starting flutter analysis?

becasue main problem is setting the groups and splines and properties.

Can you please help me in this? like any walkthrough or anything? 

and can you also ask him that how to build equivalent model of ing or complete aircraft in NX NASTRAN?

 

Regards

Shery