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thinh pham

Import pressure using linear interpolation

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Hello everyone, I'm doing a analysis to find the displacement and stress on a wing under the pressure field. And I imported the pressure field using linear interpolation with the data export from Ansys. And I have encountered a problem, the pressure field supposed to act in the outer surface of the wing skin. But instead only a part of the pressure is acting in the outer surface,other part acting in the inner surface of the wing. Could anyone tell me, why is that happening? And how can I correct it? 

I would be very grateful to receive your answers. Please help me out! 

Thank you so much!

P/s: I have uploaded here, the picture of my problem, the .hm file, and the pressure file, if you need to see it. 

press.PNG

6-9.hm

pressure8-6.csv

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Hi,

I am not sure what reason is. But to fix it, you can enter panel tools>normal, reverse normal of elems with "red" color outward

then enter analysis>pressure>update . select all pressure, set direction as "normal" then click update > vector > update

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15 minutes ago, tinh said:

Hi,

I am not sure what reason is. But to fix it, you can enter panel tools>normal, reverse normal of elems with "red" color outward

then enter analysis>pressure>update . select all pressure, set direction as "normal" then click update > vector > update

Hi, thank you for your help. I've done what you told me. But In the update radio button, there is no option for linear interpolation. So after a reverse normal of element with red color outward, I recreated the pressure. And the result is opposite. And not all the pressure is acting on the outer surface as you can see in the picture below. What else can I do to fix it? Please!

press2.PNG

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Normal vector is the same for the mesh. So if you got different pressure by doing mapping, the only cause is in your CSV file.

However, it seems to me logic. You have always different pressure between faces. By this way we got the lift, right?

Anyway, check you CFD pressure again.

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4 minutes ago, Q.Nguyen-Dai said:

Normal vector is the same for the mesh. So if you got different pressure by doing mapping, the only cause is in your CSV file.

However, it seems to me logic. You have always different pressure between faces. By this way we got the lift, right?

Anyway, check you CFD pressure again.

Thank you so much for your answers!

 Yes the different pressure between upper face and lower face make lift, but the problem I got here is that the pressure is not all acting on the outer surface. I have rechecked the CFD pressure again as you told me (even though I've check it multiple times before). This problem is so weird, I used the pressure file to import into other model, and it's find, all the pressure is acting on the outer surface. Don't know why it's different for this model. 

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1 hour ago, thinh pham said:

Hi, thank you for your help. I've done what you told me. But In the update radio button, there is no option for linear interpolation. So after a reverse normal of element with red color outward, I recreated the pressure. And the result is opposite. And not all the pressure is acting on the outer surface as you can see in the picture below. What else can I do to fix it? Please!

press2.PNG

 

 

In update panel, you need not to provide linear interpolation, we just update "vector" . Do step by step as I guide first

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19 minutes ago, tinh said:

 

 

In update panel, you need not to provide linear interpolation, we just update "vector" . Do step by step as I guide first

Hi I did as you told, I choose the pressure in loads and only update the vector. I got the pressure field all are acting on the outer surface. But then I noticed that the magnitude for the pressure seems to be multiplied to 10^4 times, not the original one. I also send the picture illustrated what I done in the update. Could you tell me, what I've done wrong please?

Thank you so much!

after.PNG

update.PNG

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Hi,

I am not sure. maybe => altair's bug :D

 

anyway, I found that in your csv file, pressure values are in different sign (sometimes plus, sometimes minus)

so it generates reversed pressure vector

Open it by excel and use abs function to unify pressure values. Then import it again => ok

 

sample:

pressure8-6___.csv

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19 minutes ago, tinh said:

Hi,

I am not sure. maybe => altair's bug :D

 

anyway, I found that in your csv file, pressure values are in different sign (sometimes plus, sometimes minus)

so it generates reversed pressure vector

Open it by excel and use abs function to unify pressure values. Then import it again => ok

 

sample:

pressure8-6___.csv

Oh, so it's because of the negative pressure value which caused the reversed vector. I got it. Thank you so much to help me out. I'm very grateful!

tinh likes this

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Suddently thinking that, if pressure values are all  minus or all plus then how the wing can fly?

Do you still think pressure vectors need to be unified?

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46 minutes ago, tinh said:

Suddently thinking that, if pressure values are all  minus or all plus then how the wing can fly?

Do you still think pressure vectors need to be unified?

No, I don't think the vector need to be unified anymore. I think the first picture I posted in the question is correct. It's not wrong. First I thought that the pressure value I import to HyperMesh will maintain its value(include the sign) so that, the vector should be unified. But then when recheck the imported pressure value. It's all positive, so the vector of the negative one must be at the opposite direction. 

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