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Subject: Re: FSI/Fluid30 + Solid98 + Damping?
Author: Olaf Heintze
Date: 2008-10-07 16:51:13

Alessandro,

I did not use the Solid98 element yet. Although, I have read in the
manual that pressure is an appropriate surface load. In my understanding
the FSI flag results in a coupling of the acoustic wave equation and the
EOM of the structure to be solved in a coupled manner. But you did not
specify the FSI flag via the sf-command. Therefore, I assume that the
pressure DOF from your Fluid30 does not interfere with your Solid98. For
more info check Chapter 8 in the ANSYS Theory Reference as well as the
Fluid30 Element Description.

BTW, please follow the rules of the list by, e.g., providing an
appropriate signature. ( http://www.xansys.org/rules.html )

Best regards,
Olaf


German Aerospace Center (DLR)
Member of the Helmholtz-Association

Institute of Composite Structures and Adaptive Systems

Dr. Olaf Heintze

Braunschweig, Germany


> -----Original Message-----
> From: xansys-bounces_at_xansys.org [mailto:xansys-bounces_at_xansys.org] On
> Behalf Of Alessandro Bellina
> Sent: Tuesday, October 07, 2008 4:23 PM
> To: ANSYS User Discussion List
> Subject: Re: [Xansys] FSI/Fluid30 + Solid98 + Damping?
>
> Olaf,
> Thank you for your answer. I did manage to get it to work. The issue
> was that I wasn't using EMODIF to change the type of the elements in
> the vicinity of the fluid/structure interface. I thought that just
> using TYPE would do the trick...
>
> Have you used Solid98? If you have, do you get pressure values at
> their nodes even though they are structural?
>
> Thanks for the help,
>
> Alessandro
>
>
> On Oct 7, 2008, at 2:22 AM,
> wrote:
>
> > Allessandro,
> >
> > There is one more thing to do to have the effect of a boundary
> > impedance
> > to be taken into account. You need to mesh the fluid30 elements in
> > contact with your structure having the FSI flag switched on:
> > et,'YOURELEMENTTYPE#',fluid30,,0
> > All other fluid elements will be meshed w/o the FSI flag
> > et,'YOURELEMENTTYPE#',fluid30,,1
> > Furthermore (as you did), you need to specify the boundary impedance
> > mp,mu,'YOURMATERIAL#','YOURIMPEDANCEVALUE'
> > and set the impedance flag by selecting all elements in touch with
the
> > structure and specifying the surface load
> > sf,all,impd,1
> >
> > It seems to work for me. Hope that helps.
> >
> > Best regards,
> > Olaf
> >
> >
> > German Aerospace Center (DLR)
> > Member of the Helmholtz-Association
> >
> > Institute of Composite Structures and Adaptive Systems
> >
> > Dr. Olaf Heintze
> >
> > Braunschweig, Germany
> >
> >> -----Original Message-----
> >> From: xansys-bounces_at_xansys.org [mailto:xansys-bounces_at_xansys.org]
On
> >> Behalf Of Alessandro Bellina
> >> Sent: Tuesday, October 07, 2008 12:11 AM
> >> To: xansys_at_xansys.org
> >> Subject: [Xansys] FSI/Fluid30 + Solid98 + Damping?
> >>
> >> Hello,
> >> I am under the impression that to accurately model a structure
> >> submerged in a fluid, damping needs to be added to the system (i.e.
> >> Ansys doesn't automatically take this into account.) Because of
this
> >> I've added a "mu" parameter to the boundary fluid30 elements
> >> (touching
> >> the FSI). I've also turned on the IMPD flag for the fluid elements.
> >> However, I am not finding this to take any effect. Regardless of
the
> >> value of "mu", the model is not damping at the fluid-structure
> >> boundary. Any of you have dealt with this issue?
> >>
> >> Thanks,
> >>
> >> Alessandro
> >>
> >> Alessandro A. Bellina
> >> bellina_at_illinois.edu
> >> ---
> >> Graduate Student
> >> Bioacoustics Research Laboratory
> >> Electrical and Computer Engineering
> >> ---
> >>
> >>
> >>
> >>
> >>
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> > ^----------------------------------------------------
>
> Alessandro A. Bellina
> bellina_at_illinois.edu
> ---
> Graduate Student
> Bioacoustics Research Laboratory
> Electrical and Computer Engineering
> ---
>
>
>
>
>
> ^----------------------------------------------------
> | XANSYS web - www.xansys.org |
> | XANSYS blog - xansys.blogspot.com |
> | The Online Community for users |
> | of ANSYS, Inc. Software |
> | Hosted by PADT - www.padtinc.com |
> ^----------------------------------------------------
Posts possibly associated with message #95373AuthorDateScore
95365FSI/Fluid30 + Solid98 + Damping?Alessandro Bellina 2008/10/06 
95366Re: FSI/Fluid30 + Solid98 + Damping?Olaf Heintze2008/10/0710
95372Re: FSI/Fluid30 + Solid98 + Damping?Alessandro Bellina 2008/10/07 
95373Re: FSI/Fluid30 + Solid98 + Damping?Olaf Heintze2008/10/07