XANSYS Message: 92724 [Go back to message list] [bookmark on del.icio.us]
No rating yet Subject: Re: [STRU] Fluid Volume Displacement in ANSYS Author: anlafuente_at_etsii.upm.es Date: 2008-04-07 17:51:43Dear Ram,
I'm dealing with a problem similar to yours and I also needed the bulk modulus of a fluid which, in my case, is air. I was very curious about how you had estimated this value for a non-solid material. Is not so straightforwrd for me and i'm kind of new in all these things. Could you please give me a hand on this?
Thanks in advance
Regards
Antonio
> Dear Keith, > > Thanks for the reply. It is a good approach. Since, the fluid is going to > fill the gap generated due to structural deflections, the fluid > properties are trivial. First, I tried with the bulk modulus of the fluid > , by finding the equivalent Young's modulus. But later realised that it > won't work as the fluid is not actually "compressed" in the analysis. But > is there any base for assuming E=1 and nu=0?. Does it reflect any free > space?. Kindly explain me. > > I've tried a similar approach, with some trial values for E and nu. After > the analysis is over, I noted the initial volume, then issued UPGEOM > command to find the final volume. But I couldn't match the answer with > that of the test value. > > Thanks & Regards, > Ram Balasubramanian > Senior Engineer - CAE, > Chennai, India. > > > > ----- Original Message ----- > From: "Keith DiRienz" > To: "ANSYS User Discussion List" > Subject: RE: [Xansys] [STRU] Fluid Volume Displacement in ANSYS > Date: Fri, 04 Apr 2008 14:28:48 -0800 > > > Ram, > I would suggest meshing the fluid volume with SOLID45's with a > modulus of 1 psi and a NUXY of zero. Then use NLGEOM,ON and do the > analysis. You can then get the volume of the fluid using ETABLE > and SSUM. Do the analysis at zero pressure and at your actual > pressure to get the change in volume. Below is a simple input file > to illustrate the procedure. > Keith > > Keith DiRienz, P.E. > FEA Technologies > Email: fea-technologies_at_cox.net > Web site: http://members.cox.net/fea-technologies > "A man with a watch knows what time it is, a man with 2 watches is > never sure." > -------------------------------------------------------------------------------------------------------------------- > ! This sample input file creates a block whose > ! exterior is meshed with SHELL63 and the interior > ! is meshed with SOLID45's which have an EX=1 and NUXY=0. > ! Internal pressure is imposed on the shells. > ! NLGEOM is activated. After solution in /POST1 > ! the volume of the SOLID45's is obtained. You can do > ! solution with zero pressure to get the original volume. > ! > /prep7 > block,0,2,0,2,0,2 > et,1,63 > et,2,45 > type,1 > mat,1 > real,1 > esize,.25 > amesh,all > type,2 > mat,2 > real,2 > vmesh,all > ! > r,1,.1 > ! > ex,1,30e6 > nuxy,1,.3 > ! > ex,2,1 > nuxy,2,0 > ! > esel,s,type,,1 > nsle > sf,all,pres,1000 > ! > nsel,s,loc,x,0 > nsel,r,loc,y,0 > nsel,r,loc,z,0 > d,all,ux,0,0,,,uy,uz > nsel,s,loc,x,0 > nsel,r,loc,y,0 > nsel,r,loc,z,2 > d,all,ux,0,0,,,uy > nsel,s,loc,x,0 > nsel,r,loc,y,2 > nsel,r,loc,z,0 > d,all,ux,0 > ! > allsel > finish > ! > /solu > nlgeom,on > lnsrch,on > save > ! > solve > finish > ! > /post1 > esel,s,type,,2 > nsle > ! > etable,volu,volu > ! > ssum ! This prints the new volume > ! > --------------------------------------------------------------------------------------------------------------------- > At 12:16 PM 4/4/2008, you wrote: > > Thanks Chris and Anker, Chris:You are right. If the profiles of the > parts > > are simple cylinders , I can use the thick cylinder formulae to > calculate > > the volume change. But in case of complex geometry, I need a tool > for > > easily calculating this change. So I raised this query. Jan:Thanks > for > > the reply. You've guided me in another possible direction,i.e., > without > > modelling the fluid. Can you kindly explain further , how to > extract the > > face elements and change in volume. Any small clue will also be > very > > helpful for me. Sorry, for the delayed response, on this thread. I > was > > trying other methods for this problem. > > > > Thanks & Regards, > > Ram Balasubramanian > > Senior Engineer - CAE, > > Chennai, India. > > > > > > ----- Original Message ----- > > From: "Jan Christian Anker" > > To: "ANSYS User Discussion List" > > Subject: RE: [Xansys] [STRU] Fluid Volume Displacement in ANSYS > > Date: Sat, 15 Mar 2008 16:29:46 +0100 > > > > > > component. I want to find the additional volume consumed due to > > structural > > deflection.> > > < How to proceed with such analysis?. Fluid 80 element doesn't > appear > > to > > suit this problem.> > > > > Why model the fluid? Assuming that you know the pressure everywhere > > in the > > fluid, you can apply the pressure to the wetted surfaces and do a > > static > > analysis. Knowing the displacements, you can get the volume change > by > > summing the volumes between the un-deformed element face and the > > deformed > > and displaced element face. > > > > I have done this in the past in APDL (but cannot find the code > > anymore). > > > > Best Regards, > > Jan Christian Anker > > __________________________________________________ > > | ANKER - ZEMER Engineering AS > > | e-mail: jc.anker_at_anker-zemer.no > > | Phone: +47 22 06 44 21 > > | Visitors' Address: Aslakveien 14 (Inng. A), R