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Nonlinear wind pressure load on a cylindrical surface

Nonlinear wind pressure load on a cylindrical surface

Nonlinear wind pressure load on a cylindrical surface

(OP)
Hi,
I’m trying to model nonlinear wind pressure load on a cylindrical surface (see attachment). I think I should use cylindrical coordinate and function dependent pressure load. Does anyone have an idea how to create a function for this? Pressure should change in proportion to angle.

Regards
VonFea

RE: Nonlinear wind pressure load on a cylindrical surface

You should create a cylindrical CSYS and use the THETA direction to vary the load.

Seif Eddine Naffoussi, Stress Engineer
www.Innovamech.com
33650 Martillac – France

RE: Nonlinear wind pressure load on a cylindrical surface

(OP)
I know I should use cylindrical CSYS and THETA direction to vary the load, but I don't know how to do it in practice.

Here is the function I have created (I think you can find my mistake here more quickly). X is angle in radians and Y is factor to multiply basic pressure. I think the problem is how to tell that X=THETA. When I expand my load I get only linear distribution and I know it's wrong.
http://files.engineering.com/getfile.aspx?folder=7...

Regards
VonFea

RE: Nonlinear wind pressure load on a cylindrical surface

In fact you can do it by using the Data Surface powerful tool.
Here is an example I made quickly to apply pressure on element depending on the Theta angle.


http://files.engineering.com/getfile.aspx?folder=6...

step by step:

1/ go to data surface editor and choose Tabular Data Surface


http://files.engineering.com/getfile.aspx?folder=c...

2/ Under Variation type choose XYZ Table, under Data Options select Scalar and hit Options to select your cylindrical CSYS.


http://files.engineering.com/getfile.aspx?folder=7...


http://files.engineering.com/getfile.aspx?folder=1...

3/ Under Define Variation Data Select Define Data and hit Theta (you can also vary the load in Z at the same time) choose a number of divisions (six for your case).
R, T, Z must appears in the dialog box if you properly selected the cylindrical CSYS:


http://files.engineering.com/getfile.aspx?folder=e...


4/ Now fill your table with the THETA value and P value to be applied and save the data surface as shown in the next figure:


http://files.engineering.com/getfile.aspx?folder=4...

5/ Go to Load / Pressure on Element / put 1 in load value in order to take into account the data surface that you will select from the menu.
Under Method choose Data Surface and select the one you created.

6/ Tip: to visualise the load pressure with a magnification scale, go to View Options (F6) Labels, Entities and Color / Load Vectors / select scale by magnitude and hit OK.

Hope this helps,



Seif Eddine Naffoussi, Stress Engineer
www.Innovamech.com
33650 Martillac – France

RE: Nonlinear wind pressure load on a cylindrical surface

You can also visualize the pressure application as a contour plot by creating an output from the applied load.

To do so, Create a new output set from Model / Output / Create/Manage Set

Activate this output set from the model info tree and activate the load set containing the pressure application.

Go to Model / Output / From Load / Select Elemental Pressure hit OK.

Press F5 and select the output vector created for the pressure output set.

And you are done!

Regards,

Seif Eddine Naffoussi, Stress Engineer
www.Innovamech.com
33650 Martillac – France

RE: Nonlinear wind pressure load on a cylindrical surface

(OP)
Hi,
Thanks for the excellent tips. I got the nonlinear pressure, but I have little problem with the distribution. When I expand the load it shows only on half circle. Is there something wrong with my data surface?

Pressure load
http://files.engineering.com/getfile.aspx?folder=c...

Pressure load expanded
http://files.engineering.com/getfile.aspx?folder=d...

Regards
VonFea

RE: Nonlinear wind pressure load on a cylindrical surface

why not applying directly the pressure on elements ??

Seif Eddine Naffoussi, Stress Engineer
www.Innovamech.com
33650 Martillac – France

RE: Nonlinear wind pressure load on a cylindrical surface

It depends on how you 2D elements normal are orientated. Be sure that all your elements have the same normal vector. Go to F6 / Labels, Entities and colors / Element Directions / Backface shading or Normal Vectors /Ok.
So You can pick one of the CQUAD face and see in which direction the pressure will be applied. Then you will be able to edit the face, front face/ back face... to invert the pressure path. Right click on the load definition / Edit Load, click no to access to the face selection dialog box..

You can also keep the pressure definition and reverse the elements normal , Modify/Update Element/Reverse Normal..

Regards,


Seif Eddine Naffoussi, Stress Engineer
www.Innovamech.com
33650 Martillac – France

RE: Nonlinear wind pressure load on a cylindrical surface

(OP)
I check element normal vectors and those are correct.
I get error message "Unable to create 620 Load(s) on Element(s). Locations in Data Surface evaluate to zero or are outside the extents of the Data Surface." I tried to change all zero values to something else but it didn't help.

http://files.engineering.com/getfile.aspx?folder=9...

RE: Nonlinear wind pressure load on a cylindrical surface

Try to put -135, -85,-60,-30,0 instead of 225,275...
List a node at approximately Theta = 225 in the cylindrical CSYS and you will see that a negative value is shown (-85)...

Seif Eddine Naffoussi, Stress Engineer
www.Innovamech.com
33650 Martillac – France

RE: Nonlinear wind pressure load on a cylindrical surface

You welcome,

Regards,

Seif Eddine Naffoussi, Stress Engineer
www.Innovamech.com
33650 Martillac – France

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