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Error in Mechanical load summary

hi every one

 

I am having an issue in calculating sum forces which i applied on a conical surface.

 

I have CFD data in X,Y, Z & pressure Format which i got from cfd software. this text file i am reading it in  field table and applying the pressure on to the conical surface. the coordinates and the contour are matching to the CFD result. 

 

but when i am checking the mechanical load summary they are not matching to the CFD resultant force .

i.e the CFD resultant forrce is like Fx = 1000N Fy =1000n and Fz = 2000N

 

but in Nx the resultants force is Like Fx = 17000N fy = 1000n Fz = 2000N

 

X axis is along the length of cone y axis Vertical and Z axis lateral

 

plz clarify why the Fx force is not matching 

Note: all the pressures are applied normal to the surface.

7 REPLIES

Re: Error in Mechanical load summary

Try to show some steps how you apply the loads to the model and paste some screenshots, it will be easier to help. Which methode you use for application of laod?

 

I would also check the coordinate systems, with respecto to which you are checking the Mechanical Load Summary. Export of Lift and Drag is usually given in local coordinate system, and Mechanical Load Summary is by default given in Native CSYS.

Re: Error in Mechanical load summary

Thank you for your reply 

 

the Procedure i followed is 

 

1. Imported the geometry as a surface model and meshed.

cone_gem.jpg

2. creating a coordinate system which will match the CFD data

cone_cordinate_applying.jpg

( the High lighted one)

 

3. getting the CFD data in to the field 

cone_pressure_load.jpg

4. checking the pressure cloud before interpolation

cone_pressure_load_contour.jpg

5. applying pressure load

cone_pressure_load_contour_applying.jpg

6. cross verifying the interpolated data by extracting the contour

cone_pressure_contour after interpolation.jpg

7. Checking the mechanical load summary 

cone_mechanical_load summary.jpgcone_mechanical_load summary details.jpg

these are the steps i fallowed 

 

plz clarify the error 

 

Re: Error in Mechanical load summary

Can you clarify how you read forces / pressures from CFD ? Maybe you read also 'rear' surface of the cone that is not shown here (?). 

 

Another thing that may influence accuracy of readings is the difference between the meshes sizes, however such difference is too big.

 

What you can check also: units of output / import and interpolation methodes, but first check how you read forces from CFD model.

 

Re: Error in Mechanical load summary

the force is calculated by 

 

1.The total force component along the specified force vector is computed by summing the dot product of the pressure and viscous forces on each face with the specified force vector

Fa = a.Fp + a.Fv

 

Fa = total force component

a  =  specified force vector

Fp = pressure force vector

Fv = viscous force vector

 

2. there is no rear surface both in CFD and in FEM so i did not considered them

 

3. I am exporting in SI units and same has been used while Importing 

4 I have played with all the interpolation methods but the load summary is not changing 

Re: Error in Mechanical load summary

have you tried to read the forces in the way it is done on the video here (drag and lift feature?)

Check this: lift and drag

 

Re: Error in Mechanical load summary

sir

 

The cfd analysis was done in FLUENT software and the data was given to me to do the structural analysis, i have verified the process they followed.

 

note: same thing i have checked with FEMAP also the result is same  

 

karthik

Re: Error in Mechanical load summary

If you have obtained the same results from the same data using 2 different post processing tools, that suggests that the values extracted from the supplied data are correct and that maybe you should re-examine the process of obtaining the data from the source to ensure it really represents what you think it represents.