Discussion Forum

Posted: 1 decade ago Sep 5, 2010, 12:57 p.m. EDT

Hi Allesandro interesting question you have there, I would like to know too ;) The only place I have found so far for coupled damping "eigenfrequency" is in the MEMS Sensor Squeezed film example, but they use the transient and not the eigensolver there (as the modes are not sustained it seems reasonnable) One of the new features in V4 is that damping is added to i.e. Linear Elastic Model, as an optional sub-node entry (right click the physics), an not as an explicit solver case, but I expect yu have seen this already -- Good luck Ivar

Posted: 1 decade ago Sep 6, 2010, 6:24 a.m. EDT

Hi Ivar, I've tried to do with v4.0a a tutorial of v3.5a about thermoelastic damping of a beam. Even if physics is different, I think the procedure is similar to mine in the case of the FSI analysis. The analysis fails with a similar error to the one found in the FSI case. Thus I think such kind of analysis is still not possible...(or maybe it requires some tuning that I don't know...) :-(... What a pity...! An other clue about such an impossibility is the fact that there are some missing tutorials in v4.0a, which instead were present in v3.5a. Maybe the Damped Eingenfrequency analysis is still a work in progress for what concerns v4.0a. Hi, let's see in Paris! Alessandro

Posted: 1 decade ago Sep 6, 2010, 10:22 a.m. EDT

Hi have you tried to compare the low level equation of physics (3.5 physics Equations setting and V4: options prefeerences Equations on) The main difficulty remaining is to get the equivalence between old and new names of the variables, normally the physics should be the same ? -- Good luck Ivar

Posted: 1 decade ago Apr 12, 2011, 7:57 a.m. EDT

Hi Alessandro, I am new to FSI and i am trying to model a stirrer in a pot of liquid. Now this is a cantilevered vibrating stirrer and my first task is to find its 1st resonance frequency when it is submerged in the liquid. It seems you have been doing this for a while, could you please help me out with this? Also, i could not figure out how to input a vibration input condition to the stirrer, you have any idea how to do this? I am working in v3.5a only, could not get used to the new GUI !! Thanks, Pranav [QUOTE] Hi to all, I'm trying to solve some FSI models which correctly ran with version 3.5a. The models calculated the eigenfrequencies of a solid structure vibrating in a fluid environment. Thanks to the "Damped Eigenfrequency analysis", that was possible, and results were correct. Now, unfortunately with version 4.0a, without changing any BC, the eigensolver always fails with the error "singular matrix". Clearly such a study is not a "default" one (as usual, the Fluid Flow module does not have any defaul analysis for the frequency domain) and thus I don't know if it is already possible with v4.0a. I'm wondering if it is a problem regarding the Fluid Flow equations (they cannot be converted in their frequency counterpart) or regarding the eigensolver. Is this last already able to solve Damped Eigenfrequency analyses too? Is there someone which has already tried (also with other physical couplings) this kind of analysis? Thanks in advance for the answer. Alessandro [/QUOTE]

Posted: 1 decade ago Sep 26, 2012, 4:24 a.m. EDT

Hi Alessandro Have you managed to get this your 2009 Conf paper working for V4.3 I have today a similar problem in the frequency mode. Even I would like to fully forget about the fluid, just add an inertia load to the solid boundary ;) -- Good luck Ivar

Posted: 1 decade ago Apr 18, 2013, 12:59 p.m. EDT

Have you had any progress with FSI models in the frequency domain in 4.3a? I am anxious to know! Thanks

Posted: 1 decade ago Apr 18, 2013, 1:52 p.m. EDT

Hi No, and I'm stil not happy, no easy solution yet perhaps in next release. Often its release before the summer holidays ;) -- Good luck Ivar