Hey,
I'm modelling a tall stack (37.5 m high) and the main loading on it is wind load, as shown here : http://courses.cit.cornell.edu/arch264/calculators/example2.4/02.jpg . I want to model the acting wind pressure but my problem is that when I apply Pressure acting on Area in Ansys it applies it normal to the area of the stack and this is not right, the wind pressure acts in one direction only on the cylindrical surface of the stack as shown in attached picture.
I wanna know how to apply this type of load in Ansys 13.0 .
Thank you very much for your help.
Best Regards,
Omar Eladel
That is all you can do when model a 3D problem in 2D. Its better you show some pictures of the ANSYS model you have created. Then I can tell you what or what not you can do.
I uploaded the model for you.
http://www.4shared.com/file/M4mv88be/Stack.html
Thank you.
Omar, if you have access to hypermesh, what you intend to do is easy. In analysis/pressure subpanel, you can define pressure with its components which can be in any direction in any coordinate system.
Omar,
I dont have ANSYS 13.0. so I could not open the .db file. Take some pictures in Iso view, front view and top view and post them here. I assume u modeled it in 3D. If not take a picture from d best possible view.
I guess the problem is with the way you model it. I am thinking you modeled it a plane just as a circular ring. If it is so that is all what you can do.
Chennakesava,
I modeled it as a 3D Model, as a surface area, meshed it by Shell Elements and added its thickness and applied all the loads as it is but the problem is in the wind load.
The attached link contains 5 pics of the model, I hope that they are helpful in clarifying the problem to you.
http://www.4shared.com/file/x5JiqpoP/Pics.html
Good. There are really helpful in understanding your model.
If you want to apply external wind load which has its components in global X, Y directions, whatever you have shown in your first sketch is correct.
But, if you need to apply a radial/tangential pressure acting on the circumference of a circular face, you need to rotate the nodes on the circumference of the corresponding face such that they are in cylindrical/polar coordinate system.
In order to do this, first you need to create "a local cylindrical coordinate system" at the center of the circular hole. refer to ANSYS help manual on how to do this. Its straight forward. Once you create local coordinate system, those nodes on the circumference need to be rotated into that local coordinate system.
And, as you are using SHELL elements you need to adjust normals of shells also. Change the ESYS of elements to the same local coordinate system. And you should check if normals of all the shell elements point to correct direction.
I hope this information would help you.
Chennakesava,
The solution what you have said is what already Ansys does cuz it applies surface loads normal to the surface you apply it so I don't need to create "local cylindrical coordinate system".
I need to apply the pressure load in global X,Y,Z directions regardless of the surface which the load applied to. But I can't do this cuz it is applied by default in the local cylindrical coordinate system of the hole I apply the load to it.
Omar,
My bad. I was talking about FORCE load.
I dont think there is such option available in ANSYS. ANSYS only supports, I think, normal pressures. You cant even apply tangential traction loads. But there is another option one can use. You can apply the load as forces in X and Y direction.
As you have the pressure values in X, Y directions readily available, you can apply them as forces instead of pressures. Before you apply them as forces, you need to convert pressure loads into forces by taking into account the surface area exposed to particular pressure load. I think that should work well.
I'll try this if I don't find any solution but isn't there any solution to apply the load as it is (pressure) not force?
Thank you very much, Chennakesava.
I have nor used it, but using surf 154 elements seems to be your solution; http://www.kxcad.net/ansys/ANSYS/ansyshelp/Hlp_E_SURF154.html
Thank you very much Fatih :) I'll read the manual until I get what I want.
SURFXXX elements do not take any elastic properties like Young's modulus etc. They only take mass and damping. So you wont be able to model stiffness of the structure. They are used to model surface effects. For example, if you want to apply a torque load on the head of a bolt with circular head, it can be easily done using surf154 elements. I mean to say you cant use those elements alone. You should them along with other structural elements.
True. But they are to be applied over structural elements and will serve to transmit the loads to the underlying structural elements like stiff63. There will be two layer of elements, one with mechanical properties, and one with loads applied over it and sharing common nodes with the other layer.
Chennakesava, Does this mean that I mesh the geometry with SURF Elements then mesh them with SHELL elements or what shall I do ?
Fatih, How shall I do this multi-layer analysis ?
Thank you very much guys.
I dont think you can use SURF elements along with SHELL elements. I am not quite sure about this. As far as I know SURF elements are used with solid elements to model surface loads.
As per my knowledge in ANSYS, SHELL elements have nodes already rotated. So, for your problem, even if you create an overlay of SURF elements on SHELLs you may not be able to apply loads parallel to cartesian coordinate directions. Better thing would apply the pressure load by converting them to FORCEs.
Hi all,
I know it is a very old post, but I am wondering if in the end you found a way to apply pressure loads on SHELL elements with global X,Y,Z direction without converting them to forces.
Thank you!
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