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[WB] Applying pressure on prejected surface, is it possible?
 
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boris.ghislain
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Joined: 12 May 2015
Posts: 3

PostPosted: Fri Jun 12, 2015 3:07 am  Reply with quote

Hello everyone,

Even if it is my first post on this forum, All the informations availaible here helped me a lot of time. Thank you all for that.

My english is not perfect but I will try to write good english enough to be understood.

My problem is the following (and is recurrent):

I have got a pipe modeled in design modeler and I want to apply a pressure on the lateral face with Workbench Mechanical. (To simulate wind pressure for example)

And I want the pressure to be applied not normal to the surface but in the X direction (perpendicular to the pipe). And I want the pressure to be applied on the projected surface.

So I want as result that the resulting force (F) of the pressure (P) on the surface (A) is F = P x A if the surface is perpendicular to the pressure and F = 0 if the surface is parralel to the pressure. (and F = P x a x cos[alpha] depending on the angle between the pressure and the surface)

Does one of you all have a solution for me?

Thank You a lot.

Boris Ghislain
Structural Engineer in Hamon Thermal Europe, Belgium
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Martin Liddle
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Joined: 15 Aug 2008
Posts: 1274
Location: Chesterfield, UK

PostPosted: Fri Jun 12, 2015 3:37 am  Reply with quote

On 12/06/2015 11:07, boris.ghislain wrote:
Quote:
And I want the pressure to be applied not normal to the surface but in the X direction (perpendicular to the pipe). And I want the pressure to be applied on the projected surface.

So I want as result that the resulting force (F) of the pressure (P) on the surface (A) is F = P x A if the surface is perpendicular to the pressure and F = 0 if the surface is parralel to the pressure. (and F = P x a x cos[alpha] depending on the angle between the pressure and the surface)
If you were doing it in Mechanical APDL then surface effect elements are
EXACTLY what you want eg SURF154. You can probably use a command object
to get them working in Workbench (if the functionality isn't exposed in
the latest versions of Workbench). I would recommend building a very
simple test model and experimenting with the choice of KEYOPTS as it
usually takes me a few attempts before I get exactly what I want.

--
Martin Liddle, Tynemouth Computer Services,
Chesterfield, Derbyshire, UK.
www.tynecomp.co.uk

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jose.galan
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Joined: 21 Oct 2008
Posts: 140

PostPosted: Fri Jun 12, 2015 3:44 am  Reply with quote

Dear Mr. Ghislain:

You can search the ansys help for section "2.5.7.6. Using Surface Effect
Elements to Apply Loads" (Mechanical APDL > Basic Analysis Guide)

"Sometimes, you may need to apply a surface load that the element type
you are using does not accept. For example, you may need to apply
uniform tangential (or any non-normal or directed) pressures on
structural solid elements, radiation specifications on thermal solid
elements, etc. In such cases, you can overlay the surface where you want
to apply the load with surface effect elements and use them as a
"conduit" to apply the desired loads. Currently, the following surface
effect elements are available: SURF151 and SURF153 for 2-D models and
SURF152, SURF154, SURF156, and SURF159 for 3-D models."

For 2D structures, you can use SURF153 elements to apply pressures in a
certain direction, specified by a vector (face 4), and with keyopt(11)
you can control wether the pressure is applied on full or projected
area, and in the latter case, .

For 3D structures, you can use SURF156 elements to apply pressure in a
certain direction, but load is applied on full area.

Best regards,

Jose M. Galan

Assistant Professor

Constr. Eng. Dept.

Universidad de Sevilla

Spain

El 12/06/2015 12:07, boris.ghislain escribió:

Quote:
Hello everyone,

Even if it is my first post on this forum, All the informations availaible here helped me a lot of time. Thank you all for that.

My english is not perfect but I will try to write good english enough to be understood.

My problem is the following (and is recurrent):

I have got a pipe modeled in design modeler and I want to apply a pressure on the lateral face with Workbench Mechanical. (To simulate wind pressure for example)

And I want the pressure to be applied not normal to the surface but in the X direction (perpendicular to the pipe). And I want the pressure to be applied on the projected surface.

So I want as result that the resulting force (F) of the pressure (P) on the surface (A) is F = P x A if the surface is perpendicular to the pressure and F = 0 if the surface is parralel to the pressure. (and F = P x a x cos[alpha] depending on the angle between the pressure and the surface)

Does one of you all have a solution for me?

Thank You a lot.

Boris Ghislain
Structural Engineer in Hamon Thermal Europe, Belgium


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jose.galan
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Joined: 21 Oct 2008
Posts: 140

PostPosted: Fri Jun 12, 2015 3:52 am  Reply with quote

In my response I assumed that your pipe was modelled with pipe elements
(line elements). If you use shell elements, SURF154 would be your
choice, as Mr. Liddle pointed out in his post.

Best regards,

Jose M. Galan

Assistant Professor

Constr. Eng. Dept.

Universidad de Sevilla

Spain

El 12/06/2015 12:44, mfernan@us.es escribió:

Quote:
Dear Mr. Ghislain:

You can search the ansys help for section "2.5.7.6. Using Surface Effect
Elements to Apply Loads" (Mechanical APDL > Basic Analysis Guide)

"Sometimes, you may need to apply a surface load that the element type
you are using does not accept. For example, you may need to apply
uniform tangential (or any non-normal or directed) pressures on
structural solid elements, radiation specifications on thermal solid
elements, etc. In such cases, you can overlay the surface where you want
to apply the load with surface effect elements and use them as a
"conduit" to apply the desired loads. Currently, the following surface
effect elements are available: SURF151 and SURF153 for 2-D models and
SURF152, SURF154, SURF156, and SURF159 for 3-D models."

For 2D structures, you can use SURF153 elements to apply pressures in a
certain direction, specified by a vector (face 4), and with keyopt(11)
you can control wether the pressure is applied on full or projected
area, and in the latter case, .

For 3D structures, you can use SURF156 elements to apply pressure in a
certain direction, but load is applied on full area.

Best regards,

Jose M. Galan

Assistant Professor

Constr. Eng. Dept.

Universidad de Sevilla

Spain

El 12/06/2015 12:07, boris.ghislain escribió:

Quote:
Hello everyone, Even if it is my first post on this forum, All the informations availaible here helped me a lot of time. Thank you all for that. My english is not perfect but I will try to write good english enough to be understood. My problem is the following (and is recurrent): I have got a pipe modeled in design modeler and I want to apply a pressure on the lateral face with Workbench Mechanical. (To simulate wind pressure for example) And I want the pressure to be applied not normal to the surface but in the X direction (perpendicular to the pipe). And I want the pressure to be applied on the projected surface. So I want as result that the resulting force (F) of the pressure (P) on the surface (A) is F = P x A if the surface is perpendicular to the pressure and F = 0 if the surface is parralel to the pressure. (and F = P x a x cos[alpha] depending on the angle between the pressure and the surface) Does one of you all have a solution for me? Thank You a lot. Boris Ghislain
Structural Engineer in Hamon Thermal Europe, Belgium -------------------- m2f -------------------- Sent using Mail2Forum (http://www.mail2forum.com [1] [1 [1]]). Read this topic online here: http://xansys.org/forum/viewtopic.php?p=98202#98202 [2] [2 [2]] -------------------- m2f -------------------- +-------------------------------------------------------------+ | XANSYS web - www.xansys.org/forum [3] [3 [3]] | | The Online Community for users of ANSYS, Inc. Software | | Hosted by PADT - www.padtinc.com [4] [4 [4]] | | Send administrative requests to xansys-mod@tynecomp.co.uk | +-------------------------------------------------------------+
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Links:
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[1] http://www.mail2forum.com [1]
[2] http://xansys.org/forum/viewtopic.php?p=98202#98202 [2]
[3] http://www.xansys.org/forum [3]
[4] http://www.padtinc.com [4]
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| Send administrative requests to xansys-mod@tynecomp.co.uk |
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[2] http://xansys.org/forum/viewtopic.php?p=98202#98202
[3] http://www.xansys.org/forum
[4] http://www.padtinc.com
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boris.ghislain
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Joined: 12 May 2015
Posts: 3

PostPosted: Fri Jun 12, 2015 5:14 am  Reply with quote

Martin Liddle wrote:

If you were doing it in Mechanical APDL then surface effect elements are
EXACTLY what you want eg SURF154. You can probably use a command object
to get them working in Workbench (if the functionality isn't exposed in
the latest versions of Workbench). I would recommend building a very
simple test model and experimenting with the choice of KEYOPTS as it
usually takes me a few attempts before I get exactly what I want.



jose.galan wrote:


In my response I assumed that your pipe was modelled with pipe elements
(line elements).



Thank you for your quick answer!

Because the geometry of the problem is more complex than a simple pipe, I use Solid 186 and Solid187 elements.

Martin Liddle wrote:


For 3D structures, you can use SURF156 elements to apply pressure in a
certain direction, but load is applied on full area.


In fact, this is the same problem that I get with Solid186/Solid187 elements
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janet.wolf
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Joined: 25 Nov 2013
Posts: 27
Location: Houston, TX

PostPosted: Fri Jun 12, 2015 6:33 am  Reply with quote

I think you want SURF154 with KEYOPT(11) set to 1 and the load applied to
face 5 of the element.

Janet Wolf, PMP, PE
Trendsetter Vulcan Offshore
Janet.wolf@vulcanoffshore.com
Tel: 281-944-2824

-----Original Message-----
From: Xansys [mailto:xansys-bounces@xansys.org] On Behalf Of boris.ghislain
Sent: Friday, June 12, 2015 7:15 AM
To: xansys@xansys.org
Subject: Re: [Xansys] [WB] Applying pressure on prejected surface, is it
possible?


Martin Liddle wrote:
Quote:

If you were doing it in Mechanical APDL then surface effect elements
are EXACTLY what you want eg SURF154. You can probably use a command
object to get them working in Workbench (if the functionality isn't
exposed in the latest versions of Workbench). I would recommend
building a very simple test model and experimenting with the choice of
KEYOPTS as it usually takes me a few attempts before I get exactly what I
want.



jose.galan wrote:
Quote:


In my response I assumed that your pipe was modelled with pipe
elements (line elements).




Thank you for your quick answer!

Because the geometry of the problem is more complex than a simple pipe, I
use Solid 186 and Solid187 elements.


Martin Liddle wrote:
Quote:


For 3D structures, you can use SURF156 elements to apply pressure in a
certain direction, but load is applied on full area.



In fact, this is the same problem that I get with Solid186/Solid187 elements






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Martin Liddle
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Joined: 15 Aug 2008
Posts: 1274
Location: Chesterfield, UK

PostPosted: Fri Jun 12, 2015 8:09 am  Reply with quote

On 12/06/2015 13:14, boris.ghislain wrote:
Quote:
Martin Liddle wrote:
Quote:

For 3D structures, you can use SURF156 elements to apply pressure in a
certain direction, but load is applied on full area.

I did not say that and it isn't true with a careful of selection of
options. Please be more careful with your quoting in future.

Also your signature is missing from this post. Please be careful to
attach a signature to all posts to XANSYS.

--
Martin Liddle, Tynemouth Computer Services,
Chesterfield, Derbyshire, UK.
www.tynecomp.co.uk

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christopher.wright
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Joined: 17 Jun 2009
Posts: 927

PostPosted: Fri Jun 12, 2015 3:25 pm  Reply with quote

On Jun 12, 2015, at 5:07 AM, boris.ghislain wrote:

Quote:
I have got a pipe modeled in design modeler and I want to apply a
pressure on the lateral face with Workbench Mechanical. (To
simulate wind pressure for example)

And I want the pressure to be applied not normal to the surface but
in the X direction (perpendicular to the pipe). And I want the
pressure to be applied on the projected surface.

Give some thought to the fact that fluid pressure always acts normal
to a bounding surface. There may be a component of viscous or
turbulent shear, but the effects are very small. Thus mother nature
in her wisdom makes it possible to apply a normal pressure to the
upstream face of the pipe which is statically equivalent to the
pressure applied along a diameter.

Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw@skypoint.com | this distance" (last words of Gen.
.......................................| John Sedgwick, Spotsylvania
1864)
http://www.skypoint.com/members/chrisw/



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boris.ghislain
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Joined: 12 May 2015
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PostPosted: Wed Jun 17, 2015 1:32 am  Reply with quote

christopher.wright wrote:

Give some thought to the fact that fluid pressure always acts normal
to a bounding surface. There may be a component of viscous or
turbulent shear, but the effects are very small. Thus mother nature
in her wisdom makes it possible to apply a normal pressure to the
upstream face of the pipe which is statically equivalent to the
pressure applied along a diameter.


You are right Christopher. I wanted to make some simplifications, but sometimes simplifications are more difficult than the true behavior of the system.

For your information, I explain what I did to solve (or avoid) my problem:

I wanted to model a wind pressure on a duct and what I did is:

-defining a new cylindrical coordinate system (with the origin in the center of the cross section of the duct)

-Apllying a normal pressure on the outer face of the duct with a magnitude defined by a function. The function variable is the "y" coordinate of the cylindrical coordinate system (which is the angular value) and the function is a fourier serie.


I think this way is the simplest way to model wind pressure on a pipe without losing the information on the roundness variation of the pipe itself.

Thank you all for your posts.
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Boris Ghislain
Structural engineer at HTEB S.A. - Belgium
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