XANSYS Message: 92731 [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: 2008-04-08 04:16:44Dear Ram,
Thank you. I forgot telling you that I'm considering my fluid incompressible since it will be filling a narrow gap! In that situation there should be a way of calculating this equivalent Youngs Modulus!
Tanks and regards
Antonio
> Dear Antonio, > > In my case, the fluid is brake fluid, for which the bulk modulus is > readily available with the manufacturer. To my knowledge, one can estimate > bulk modulus for nearly incompressible fluids like water, oil or solids. > But, since air is compressible, I think it will have near zero bulk > modulus. Correct me if I'm wrong. > > Thanks & Regards, > Ram Balasubramanian > Senior Engineer - CAE, > Chennai, India. > > > > > ----- Original Message ----- > From: anlafuente_at_etsii.upm.es > To: "ANSYS User Discussion List" > Subject: RE: [Xansys] [STRU] Fluid Volume Displacement in ANSYS > Date: Mon, 7 Apr 2008 19:52:42 +0200 (CEST) > > > Dear 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