[clementbrun]

Hello, I would like to solve a vibration problem. To put it simply, I have a glass tube held in certain places. This tube is placed in a flow. In reality, the tubes break and I suspect that they are in resonance. 


I've done some CFD simulations to get the frequencies induced by the water. I also ran mechanical simulations using frequency analysis to find out whether the orders of magnitude are the same. 
It turns out that the frequencies induced by the water are around 10Hz and the natural frequencies of the glass tube are 80Hz. Admittedly these are not the same frequencies, but in reality the tubes break. By adding a fixing point in the middle of the quartz, I realise that the first frequency of the tube is 700Hz. This is a far cry from the 11Hz induced by the flow and the 80Hz of the initial configuration.

My questions are as follows:
- Is my reasoning correct?
- How can we determine a "frequency safety margin", i.e. at what frequency difference (between those induced by the water and the natural frequencies of the glass tubes) can we assume that the tube won't break?


Thank you for your answers