[fredicenci]

Hello all,

My problem is a cylinder attached to a spring (no damping). The cylinder is immersed on air. It should result in a sine with little decay (because water viscosity). However, what I find is a small amplification of the sine, seems like the problem is gaining energy somehow. Attached are pictures of the transverse amplitude through time.

First, I thought the problem was mesh resolution and residuals, but decreasing these factors doesn’t help.
Secondly, I tried to put a little damping (C = zeta*wn*2*m), with zeta = 0.5%. But the results give me a decay with zeta = 0.14%.

I have a guess that the problem may be my BC. I put a fixedValue inlet with velocity (0,0,0) and all domain with zero velocity as well.

Here is the link ok my testcase. https://drive.google.com/file/d/1Fmm...UIkeKyhJ7/view

May someone give me a hint of what could be the issue?

Thanks in advance.

39146173_1893991114026776_2290834838703308800_o.jpg

39188348_1893991104026777_1563691592680734720_o.jpg

[Zhi Cheng]

Hi! Excuse me, can I know how to get the oscillating amplitude change or the spring length change? like your pic showing the change of y?
Best regards,
ZHI CHENG

[anon_q]

Originally Posted by Zhi Cheng

Hi! Excuse me, can I know how to get the oscillating amplitude change or the spring length change? like your pic showing the change of y?
Best regards,
ZHI CHENG

Download the case and take a look to the file dynamicMeshDict.